Research | NightOwling.com

Timing of food intake during simulated night shift impacts glucose metabolism: a controlled study

Cardiometabolic Chrononutrition Chronotype

This controlled laboratory study tested how meal timing affects glucose metabolism during simulated night shifts. Eleven healthy men completed four consecutive night shifts and were assigned either to eat a 1:30 a.m. meal or avoid eating overnight while keeping total daily calories the same. Blood sugar control (glucose AUC) worsened only in those who ate at night, while those who avoided overnight meals maintained more stable glucose levels. Insulin responses increased after returning to day shifts in both groups, suggesting that night work itself can strain metabolism.

Association Between Rotating Night Shift Work and Risk of Coronary Heart Disease Among Women

Cardiometabolic Cardiovascular Circadian

This prospective study tracked over 189,000 nurses across 24 years to examine whether rotating night-shift work raises the risk of coronary heart disease (CHD). Women with longer durations of rotating night shifts had a small but significant increase in CHD risk compared to women who never worked nights. The risk was strongest among those with many years of rotating night duty and appeared to lessen after workers stopped night shifts, suggesting that some of the excess risk may decline over time.

Effects of the Internal Circadian System and Circadian Misalignment on Glucose Tolerance in Chronic Shift Workers

Cardiometabolic Chrononutrition Circadian

This randomized crossover study tested how circadian timing and circadian misalignment affect glucose tolerance in chronic shift workers. In tightly controlled lab conditions, workers ate identical meals during their biological morning and evening, both with and without circadian misalignment. Results showed that blood sugar control was 6–7% worse in the biological evening compared to the morning, and that circadian misalignment independently worsened glucose tolerance by about 6%, even with the same sleep, food, and activity schedules. The impairments were tied to weaker insulin secretion in the evening and reduced insulin sensitivity under misalignment.

Near‑Crash Driving Events After Night‑Shift Work: Real‑World Driving Study

Circadian Commute safety Epidemiology

This experimental study tested driving performance in 16 night-shift workers using an instrumented vehicle on a closed track. Each participant completed two daytime drives: one after a normal night’s sleep and one immediately after a 12-hour night shift. After night duty, drivers showed marked increases in drowsiness (measured by EEG, eye movements, and blink duration), lane excursions, and performance lapses. Eleven near-crash events occurred in the post–night shift condition, but none after normal sleep. All near-crashes happened after 45 minutes of driving, showing that risk builds with time on the road.

Night Shift Work and Erosive Esophagitis: Endoscopy‑Verified Association

Chrononutrition Circadian Cross-sectional

This large study looked at more than 6,000 male shipyard workers in South Korea to see whether working night shifts was linked to digestive problems. All participants underwent endoscopy to check for erosive esophagitis, a condition where repeated acid reflux damages the lining of the esophagus. The results showed that men working night shifts were more likely to have erosive esophagitis compared to those who only worked daytime hours. Lifestyle habits also played a role: obesity, smoking, and frequent drinking increased the risk, while workers who had Helicobacter pylori infection were less likely to show signs of the condition.

Armodafinil Improves Simulated Driving and Alertness in Shift Work Disorder

Armodafinil Circadian Cognitive function

This randomized crossover study tested whether a single 150 mg dose of armodafinil could help night-shift workers with Shift Work Disorder stay alert and drive more safely. Twenty participants completed overnight lab sessions with either armodafinil or placebo. Compared to placebo, armodafinil reduced lane drifting and off-road errors in a driving simulator, increased time before falling asleep in lab tests, and improved performance on a creativity task. Benefits lasted up to 9.5 hours after dosing, covering the critical early morning period when many shift workers are commuting home.

Negative Impacts of Shiftwork and Long Work Hours (NIOSH Review)

Cardiometabolic Chronic disease Circadian

This umbrella review from the National Institute for Occupational Safety and Health (NIOSH) outlines how shift work and long hours affect healthcare workers, especially nurses. Across studies, these schedules are consistently linked to short and poor-quality sleep, lower job performance, higher rates of obesity and workplace injuries, and greater risk of chronic illnesses like heart disease and diabetes. Fatigue also raises the chance of medical errors and commuting accidents.

Exposure to Shift Work as a Risk Factor for Diabetes: Workplace Study

Aging Cardiometabolic Circadian

This cross-sectional survey of 1,111 retired U.S. adults (age 65+) examined whether years of shift work were linked to diabetes later in life. Participants reported their lifetime shift work exposure and whether they had diabetes requiring medication. Compared to those who never worked shifts, people with any history of shift work had about 1.5–2 times higher odds of reporting diabetes, even after adjusting for gender and body mass index. Shift work exposure was also associated with higher BMI.

Two 15‑Minute Naps on the Night Shift: Effects on Sleepiness, Fatigue, and HRV

Cardiovascular Circadian Fatigue

This field study followed 15 night-shift nurses to test whether two 15-minute naps during a shift could improve alertness and physiological stress markers. While both nap and no-nap groups reported rising fatigue and sleepiness toward early morning, the nap group showed more stable heart rate variability, with a lower LF/HF ratio and no sudden morning spike in parasympathetic activity. These findings suggest short naps may help reduce physiological strain even if they don’t immediately change how tired workers feel.

Impact of Shiftwork on IBS and Functional Dyspepsia: A Hospital Study

Cross-sectional Field GI & microbiome

This hospital-based cross-sectional study surveyed 207 nurses and nursing assistants to examine the link between shift work and digestive disorders. Rotating shift workers were about twice as likely to report irritable bowel syndrome (33%) compared with day workers (17%). Functional dyspepsia was equally common in both groups, but poor sleep and high stress increased the odds of both conditions. Rotating shift work itself remained an independent risk factor for IBS even after accounting for gender and sleep quality.

Risk of Miscarriage and Occupational Activity: Systematic Review and Meta‑analysis

Pregnancy, Reproductive health, Night-shift workers, Systematic review, Meta-analysis, Shift work, Occupational, Occupational health, Work schedules & policy, Permanent nights, Long hours

This systematic review and meta-analysis pooled data from 30 studies to assess whether occupational factors influence miscarriage risk. Fixed night work was linked to about a 50% higher risk of miscarriage, while rotating shifts, long weekly hours, prolonged standing, heavy lifting, and high physical workload showed only small increases in risk. In higher-quality studies, the associations for long hours and standing were weaker. Overall, the findings suggest modest risks, with the most consistent evidence for fixed night shifts.

Shift Work and Vascular Events: Systematic Review & Meta‑analysis (BMJ)

This BMJ systematic review and meta-analysis combined data from 34 studies involving more than two million people to examine the cardiovascular risks of shift work. Compared with daytime workers, shift workers had a modestly higher risk of heart attack, ischemic stroke, and other coronary events. The risks varied across studies, and evening shifts were not linked to increased coronary disease. Importantly, shift work was not associated with higher overall or cardiovascular mortality.

Rotating Night Shift Work and Risk of Type 2 Diabetes: Two Prospective Cohort Studies in Women

Cohort, Diabetes, Metabolic health, Epidemiology, Women, Nurses, Rotating shifts, Night shift, Shift work, Occupational health, Long hours, Health outcomes

This large prospective study combined data from more than 177,000 U.S. nurses followed for up to 20 years. Women who worked rotating night shifts for longer periods had a higher risk of developing type 2 diabetes. The risk rose with years of exposure, with those reporting 20 or more years of rotating night duty showing the greatest increase. Part of the effect was explained by higher body weight, but even after accounting for weight and lifestyle factors, long-term shift work was still linked to greater diabetes risk.

Armodafinil for Treatment of Excessive Sleepiness Associated with Chronic Shift Work Disorder

Sleep, Shift Work Disorder (SWD), Night-shift workers, RCT, Armodafinil, Wake-promoting, Alertness, Attention, Fatigue & alertness, Clinical, Clinical trial, Occupational health, Commute safety

This 12-week, multicenter randomized controlled trial tested whether armodafinil could reduce excessive sleepiness in 254 night-shift workers diagnosed with Shift Work Disorder. Taken before each shift, armodafinil significantly improved objective wakefulness, with patients staying awake longer on lab sleep tests. Compared with placebo, more patients reported overall clinical improvement, and diaries showed reduced sleepiness during night work, in the lab, and on the commute home. Armodafinil also improved memory and attention scores, and did not interfere with daytime sleep. The medication was generally well tolerated.

Circadian misalignment and adverse cardiometabolic consequences in humans

Circadian, Cardiometabolic, Lab, Physiology, Endocrine & hormones, Metabolic health, Glucose, Blood pressure, RCT, Protocol, Sleep, Night work, Health outcomes

This controlled laboratory study tested how circadian misalignment—when eating and sleeping occur about 12 hours out of sync with the body’s internal clock—affects health. Ten healthy adults followed a shifted schedule for 10 days while total sleep time was maintained. Misalignment lowered leptin, raised glucose and insulin levels, increased blood pressure, reversed the normal daily cortisol rhythm, and reduced sleep efficiency. In some participants, post-meal blood sugar reached levels typical of prediabetes. These changes occurred even though total sleep was not reduced.

Caffeine vs Nap vs Placebo on Memory and Performance

Caffeine, Napping, Naps, Cognitive performance, Fatigue & alertness, RCT, Lab, Sleep, Alertness, Memory, General population, Performance

This crossover laboratory study directly compared the effects of caffeine (200 mg), a 60–90 minute nap, and placebo on three types of memory. Naps improved recall of words and boosted perceptual learning, outperforming both caffeine and placebo. In contrast, caffeine significantly impaired motor skill learning and did not improve verbal memory. These findings suggest that short naps are more effective than caffeine for supporting memory and learning.

Efficacy and Hypnotic Effects of Melatonin in Shift‑Work Nurses

Sleep, Nurses, RCT, Melatonin, Night shift, Shift work, Recovery, Fatigue & alertness, Clinical, Clinical trial, Occupational health

This randomized, placebo-controlled crossover trial examined the effects of melatonin on 86 nurses working night shifts. After completing an overnight shift, participants took either 5 mg of melatonin or placebo before attempting daytime sleep. Compared with placebo, melatonin significantly reduced sleep onset latency, allowing participants to fall asleep more quickly, and improved subjective ratings of sleep quality. It did not increase total sleep time or reduce awakenings. No adverse effects were reported.

Nurse Work Schedules, Sleep Duration, and Drowsy Driving

This prospective study asked 895 U.S. hospital nurses to log their work hours, sleep, and alertness over four weeks. Two-thirds of participants reported at least one episode of drowsy driving during the study, and 30 nurses reported drowsy driving after every shift. Risk was significantly higher for those working night shifts, shifts longer than 12.5 hours, averaging fewer than six hours of sleep, or struggling to stay awake at work.

Bright Light vs Melatonin vs Placebo in Shift Workers: Randomized Field Study

RCT, Field, Field study, Melatonin, Light, Lighting, Bright light, Fatigue & alertness, Sleep, Night work, Rotating shift workers, Shift work, Occupational health, Recovery

This randomized, placebo-controlled crossover field trial examined melatonin and bright light as countermeasures to shift-related sleep problems in 17 oil-rig workers on a rotating schedule. Workers received melatonin (3 mg before bed), timed bright-light exposure, or placebo during the first four days of night and day shifts. Melatonin reduced sleepiness during day shifts and increased total sleep by about 15–20 minutes per day. Bright light produced modest improvements in objective sleep during night shifts, but overall effects were limited. Few outcomes reached strong statistical significance, likely due to real-world variability and suboptimal timing.

Napping Plus Caffeine: Laboratory and Field Studies in Shift Workers

RCT, Lab, Field, Field study, Caffeine, Napping, Naps, Fatigue & alertness, Night-shift workers, Shift work, Safety (workplace), Performance, Occupational health, Recovery

This research combined a randomized laboratory study and a field trial to test naps, caffeine, and their combination as countermeasures for night-shift fatigue. In the lab, 68 healthy adults were assigned to one of four groups: nap only, caffeine only, nap plus caffeine, or placebo. All active strategies improved alertness and reaction times compared with placebo, but the combined approach produced the strongest benefits. In the field study with 53 shift workers, naps plus caffeine similarly reduced sleepiness and improved performance during night shifts.

Modafinil for Excessive Sleepiness Associated with Shift-Work Sleep Disorder

This three-month randomized controlled trial evaluated modafinil in 209 night-shift workers diagnosed with Shift-Work Sleep Disorder. Participants took 200 mg modafinil or placebo before each night shift. Compared with placebo, modafinil modestly increased objective wakefulness on lab sleep tests, improved attention and reduced lapses on vigilance tasks, and lowered the proportion of workers reporting accidents or near-misses during their commute home (29% vs 54%). Clinical condition ratings also improved. Daytime sleep was not affected, and side effects were generally mild, with headache the most common. Despite these benefits, many participants continued to experience significant sleepiness at night.

The Alerting Effects of Caffeine, Bright Light, and Face Washing After a Short Nap

RCT, Caffeine, Napping, Naps, Light, Lighting, Bright light, Fatigue & alertness, Alertness, Performance, Sleep, Lab, Cognitive performance, Night work

This randomized crossover study tested how different strategies influence alertness after a short daytime nap. Ten healthy adults completed five nap conditions: nap only, nap plus 200 mg caffeine, nap plus one minute of bright light, nap plus face washing, and no nap (rest only). The combination of caffeine and nap produced the strongest and most sustained improvements in both alertness and task performance. Bright light after a nap was nearly as effective for reducing subjective sleepiness but less effective for performance. Face washing provided only a brief reduction in sleepiness immediately after the nap.

Characteristics of working hours and the risk of occupational injuries among hospital employees: a case‑crossover study

Case-crossover Epidemiology Evening shifts

This case-crossover study analyzed payroll and injury records from nearly 19,000 hospital employees to see how work schedules affected accident risk. Injuries were more likely during evening shifts, on days following night shifts, and after long shifts (10+ hours). The risk also rose when employees worked three or more evening shifts in a week. By contrast, the number of night shifts, quick returns, and total weekly hours were not linked to higher accident risk. Comparing each worker’s injury shifts to their own non-injury shifts showed that it’s the timing and length of shifts, rather than shift work overall, that most influenced safety.

Effect of Suvorexant vs Placebo on Daytime Sleep in Shift Workers: Randomized Clinical Trial

Circadian Clinical Clinical trial

This double-blind, placebo-controlled trial tested suvorexant, a sleep medication, in 19 night-shift workers who struggled to sleep after shifts. Compared with placebo, suvorexant significantly increased daytime total sleep: about 1 extra hour after one week on 10 mg and more than 2 extra hours after two weeks on 20 mg. Subjective reports suggested even greater gains, with participants sleeping nearly 3 extra hours compared to placebo by the end of the study. Physician ratings confirmed the improvement, and no adverse events were reported.

High‑protein night meal and circadian measures in shift workers

Cardiometabolic Chrononutrition Circadian

This randomized crossover study tested whether eating a high-protein/moderate-carb meal at 1:00 a.m. would improve metabolism compared with a lower-protein, higher-carb meal in 14 male night-shift workers. Results showed that the protein-rich meal led to smaller glucose spikes during the night shift. However, when participants later ate a standard breakfast at the end of their shift, there were no differences in glucose, insulin, or triglyceride responses between the two meal types. In short, protein helped control blood sugar during the night meal but had no effect on the metabolism of the following breakfast.

Long Working Hours and Shift Work During Pregnancy: Obstetric and Perinatal Outcomes

Cardiometabolic Circadian Cohort

This nationwide prospective study followed nearly 100,000 pregnant women in Japan to examine how working hours and night-shift schedules affected pregnancy outcomes. Compared with nonworking women, those who worked during pregnancy had higher risks of threatened miscarriage and threatened preterm labor. Among women working 36+ hours per week with night shifts, the risk of hypertensive disorders of pregnancy was doubled. Long hours (≥36 per week) were also linked to more vacuum/forceps deliveries, and very long weeks (≥46 hours with night shifts) increased the risk of small-for-gestational-age (SGA) infants. In contrast, women working without night shifts had slightly lower odds of gestational diabetes and meconium-stained amniotic fluid.

Night Shift Work (IARC Monographs on the Identification of Carcinogenic Hazards to Humans, Volume 124)

Cancer Chronic exposure Circadian

The International Agency for Research on Cancer (IARC) reviewed epidemiologic studies, animal experiments, and mechanistic data to evaluate cancer risks from night-shift work. In humans, studies showed positive associations between long-term night work and breast, prostate, and colorectal cancers, though results were inconsistent and evidence was judged limited. In animals, altering the light–dark cycle produced sufficient evidence of carcinogenicity, with increased rates of liver, lung, and lymphoma tumors. Mechanistic studies provided strong support, showing that circadian disruption reduces melatonin, alters hormone regulation, and interferes with DNA repair. Based on this combined evidence, IARC classified night-shift work as “probably carcinogenic to humans” (Group 2A).

Night‑Shift Work, Short Sleep, and Obesity

Cardiometabolic Chronic disease Circadian

This cross-sectional study compared 200 healthcare workers in Brazil to see how night shifts affected sleep and obesity. Night-shift workers were older, slept fewer hours, and had significantly higher body weight, BMI, and abdominal circumference than day-shift workers. They also experienced more social jetlag (a mismatch between work schedules and natural sleep patterns). Night workers had nearly three times greater odds of abdominal obesity, even after adjusting for age and gender. Quality of life scores did not differ between groups.

Pilot Study: Caffeine‑Nap on Night‑Shift Alertness

Caffeine Circadian Clinical trial

This pilot crossover study tested whether a “caffeine-nap” — drinking 200 mg of caffeine just before a 30-minute nap at 3:30 a.m. — could help reduce sleep inertia during a simulated night shift. Six participants completed both caffeine and placebo nap conditions. Compared to placebo, the caffeine-nap led to better vigilant attention and less subjective fatigue in the 45 minutes after the nap. The findings suggest that combining caffeine with a short nap may be a useful fatigue countermeasure during overnight work, though larger trials are needed.

The effectiveness of bright light exposure in shift‑worker nurses: a meta‑analysis

Alertness Circadian Evidence review

This meta-analysis reviewed five intervention studies of bright light exposure among night-shift nurses. The fixed-effects analysis suggested that timed bright light during shifts reduced sleepiness, improved alertness, and lengthened daytime sleep after work. However, because of the small number of studies and large differences in methods (duration, timing, intensity), the more conservative random-effects analysis found no statistically significant benefits. The authors concluded that while bright light shows promise, current evidence is limited and more well-designed, larger trials are needed.

Night Work During Pregnancy and Preterm Birth—Register Study

Circadian Cohort Epidemiology

This large Danish cohort study followed 16,501 pregnant women to test whether night-shift work increased the risk of preterm birth. Using detailed payroll records, researchers examined timing (first vs. second trimester), intensity (number and duration of night shifts), and patterns (consecutive nights, quick returns). Across all measures, night work was not linked to a higher risk of preterm birth compared to day-only work. Even women with frequent or consecutive night shifts showed no increased risk. A weak, non-significant increase was seen in women who switched from night work in the first trimester to day-only schedules in the second trimester, but overall results supported no association.

Shift Work and Poor Mental Health: Meta‑Analysis of Longitudinal Studies

Chronic disease Circadian Epidemiology

This meta-analysis combined results from 7 longitudinal studies with over 28,000 workers to examine the link between shift work and mental health. Compared to day workers, shift workers had a 28% higher risk of poor mental health overall and a 33% higher risk of depressive symptoms. Gender differences were important: women working shifts had a 73% higher risk of depression than women on day schedules. The studies varied in design and outcomes, but overall the results support a connection between shift work and poorer long-term mental health.

Shift Work and Risk of Occupational, Transport and Leisure‑time Injury: Systematic Review & Meta‑analysis

Epidemiology Evening shifts Evidence review

This register-based case-crossover study analyzed data from more than 13,000 Danish hospital workers to examine whether shift timing and recovery periods affected injury risk. Compared to day shifts, evening shifts increased the risk of occupational injury by more than 50%, and quick returns (<11 hours between shifts) raised the risk by about 25%. By contrast, night shifts were not linked to higher injury risk, and there was no association between shift type and leisure-time or commuting injuries.

Shift Work and Shift Work Sleep Disorder: Clinical Review

Behavioral intervention Circadian Clinical

This clinical and organizational review describes Shift Work Sleep Disorder (SWD), a circadian rhythm condition affecting a substantial minority of night and rotating-shift workers. SWD is defined by excessive sleepiness, insomnia, or both, leading to reduced quality of life, poorer health, and higher accident risk. At the organizational level, SWD also creates financial costs through lost productivity and safety incidents. The review outlines current knowledge of the disorder’s causes, health impacts, and treatment approaches, including light therapy, melatonin, and cognitive-behavioral methods. It also highlights workplace strategies like improved scheduling, nap opportunities, and fatigue risk management programs, though evidence for many interventions remains limited.

Shift Work, Chronotype, and Melatonin Rhythm in Nurses (NHS II Sub‑study)

Chronotype Circadian Epidemiology

This analysis of 130 nurses in the Nurses’ Health Study II tested how shift schedules and chronotype interact to affect melatonin rhythms. Compared to day-shift nurses, rotating-shift workers on nights had greater nighttime light exposure, lower overall melatonin levels, smaller peaks, and later timing of melatonin release. Chronotype also mattered: evening types had later peaks, while morning types had earlier, stronger peaks. Importantly, the effects of shift work and chronotype combined — when work schedules aligned poorly with chronotype, melatonin disruption was more pronounced.

Short time between shifts (‘quick returns’) and risk of injury among Danish hospital workers

Cohort Epidemiology Fatigue

This cohort study analyzed payroll and injury records from more than 69,000 Danish hospital workers to test whether short recovery times between shifts increase injury risk. “Quick returns” (≤11 hours between shifts) were linked to a 39% higher risk of injury compared to standard 15–17 hour breaks. The risk was highest in the first two days following a quick return, suggesting that insufficient recovery time carries immediate safety consequences.

Bright Environmental Light Reduces Post‑Shift Sleepiness in ICU Nurses

Circadian Fatigue Fatigue & alertness

This crossover randomized trial tested whether bright environmental lighting could help ICU nurses stay alert during 12-hour night shifts. Forty-three nurses worked under either standard hospital fluorescent lighting or high-intensity white light (1,500–2,000 lx) for 10 hours. Under bright light, nurses reported less sleepiness at the end of their shift. However, they also showed more errors on psychomotor vigilance tests, suggesting that while alertness improved, sustained attention performance did not.

Comparative Study of Shift Work Effects and Injuries Among Hospital Nurses

Cross-sectional Epidemiology Fatigue

This cross-sectional study compared 275 nurses working rotating night shifts with 275 working only day shifts in a North Indian hospital. Nurses on rotating shifts reported significantly worse outcomes, including greater fatigue, more sleep problems, poorer psychological well-being, and lower job satisfaction. They also faced higher odds of needle stick injuries, especially if they worked on contract or lived off-campus. Female nurses overall reported more fatigue and psychological health challenges than males.

Night Shift Preparation, Performance, and Perception

Circadian Commute safety Fatigue

This survey study compared how emergency medicine faculty, residents, and nurses prepare for and cope with night shifts at a U.S. medical center. Nurses reported the highest use of blackout curtains, while residents relied on melatonin more than the other groups. Faculty were less likely to use pharmacologic sleep aids, less likely to eat before shifts, and less satisfied with working nights overall. Despite different routines, all groups reported feeling tired during shifts, with 4:00 a.m. as the low point. Faculty were more likely to fall asleep while driving home, though accident rates were low across all groups.

Night‑Shift Work, Genetic Risk, and Type 2 Diabetes in the UK Biobank

Cardiometabolic Circadian Cohort

This UK Biobank study examined over 270,000 participants to assess the relationship between night-shift work, genetics, and type 2 diabetes. Compared to day workers, those on rotating or occasional night shifts had higher odds of diabetes, with risk rising as the number of monthly night shifts increased (>8/month OR 1.36). Interestingly, permanent night workers did not show significantly elevated risk, suggesting that irregular or rotating schedules may be more disruptive. Genetic risk for diabetes did not interact with shift work exposure — both high- and low-genetic risk groups were similarly affected.

Psychomotor Driving Performance in Night‑Shift Nurses: Prospective Study

Circadian Commute safety Epidemiology

This prospective study tested 47 female nurses in Iran to compare driving-related performance after night shifts versus day shifts. Using the Vienna Test System, researchers measured reaction time, visual orientation, perceptual speed, and stress tolerance before and after shifts. Night-shift nurses, even with a 3-hour nap during their 12-hour duty, showed slower choice reaction times and poorer visual orientation compared to day-shift nurses. About 30% of night-shift nurses reported a traffic accident in the past year, nearly double the rate of day-shift peers.

Rotating night shift work and colorectal cancer risk in the nurses’ health studies

Cancer Circadian Cohort

This prospective cohort study combined nearly 191,000 participants from the Nurses’ Health Study and NHS II to assess whether rotating night-shift work raises colorectal cancer risk. After 24 years of follow-up, researchers found no overall link between night-shift duration and colorectal cancer. However, in detailed analysis of cancer subtypes, women with 15+ years of rotating night work had a significantly higher risk of rectal cancer (HR 1.60). Risks for proximal and distal colon cancer were not significantly elevated.

Shift Work and Sleep: Medical Implications and Management (Review)

Circadian Education & training Fatigue

This review outlines the medical consequences of shift work and provides an overview of Shift Work Sleep Disorder (SWSD), a circadian rhythm condition marked by excessive sleepiness, insomnia, or both in response to irregular schedules. It describes how circadian misalignment leads to fatigue, mental health problems, reduced physical well-being, and diminished quality of life. The review also stresses the significant economic costs of untreated SWSD and calls for greater involvement from healthcare providers and policymakers in prevention, education, and worker support.

Effect of Shift Work on Hypertension: Cross‑sectional Study

Cardiometabolic Cardiovascular Circadian

This cross-sectional study evaluated 1,953 male petrochemical workers in South Korea to examine the link between shift work and hypertension. Compared to day workers, shift workers had significantly higher odds of high blood pressure (adjusted OR 1.51). The risk was even greater for those with 20 or more years of continuous shift work, underscoring the cumulative cardiovascular burden of long-term exposure.

Night Shift Work and Depression: Meta‑analysis of Observational Studies

Circadian Epidemiology Fatigue

This meta-analysis reviewed 11 observational studies to assess whether night-shift work is linked to depression. Across nearly all study types and populations, night-shift workers had a 43% higher risk of depression compared with day workers. The association was consistent across gender, occupation, and geography, strengthening the evidence that working nights disrupts circadian rhythms in ways that affect mental health.

Randomized controlled trial of blue‑enriched light to improve alertness and performance in night shift workers

Alertness Circadian Fatigue

This randomized controlled trial compared blue-enriched lighting with standard white light during simulated night shifts in 71 night-shift workers. Across the night, both groups became sleepier, and no overall performance benefits were found with blue-enriched light. However, when exposure overlapped with the timing of melatonin rhythm peaks, participants under blue-enriched light reported less subjective sleepiness than those under standard lighting.

Reduced Tolerance to Night Shift in Chronic Shift Workers

Adaptation Age & aging Circadian

This study combined field and laboratory experiments to test how night shifts affect the body’s internal regulation of activity patterns, known as fractal regulation (FR). Compared to non-shift workers, chronic shift workers showed more disrupted and random activity rhythms during night shifts, and these disturbances persisted for up to two days afterward. The laboratory results confirmed that chronic shift workers were less resilient to circadian misalignment than non-shift workers, and those who began shift work later in life experienced even greater disruption.

The impact of meal timing on performance, sleepiness, gastric upset, and hunger during simulated night shift

Chrononutrition Circadian Fatigue

This randomized crossover study tested whether eating at night affects alertness and well-being during simulated night shifts. Ten participants were assigned to either eat a meal at 1:30 a.m. or avoid food overnight while keeping total daily calories the same. Both groups experienced sleepiness at 4:00 a.m., but those who ate at night showed greater performance impairments, while those who avoided night meals had better vigilance but reported more hunger and some stomach discomfort.

IARC Monographs on the Identification of Carcinogenic Hazards to Humans Volume 129

Cancer Monograph/Guideline Occupational health

The International Agency for Research on Cancer (IARC) reviewed decades of human and animal studies on night-shift work and cancer risk. In 2019, it classified night-shift work as “probably carcinogenic to humans” (Group 2A). This conclusion was based on limited but suggestive evidence in humans (mainly breast, prostate, and colorectal cancer in long-term night workers) and sufficient evidence in animal models showing that circadian disruption can promote tumor development.

SHIFTPLAN: Multimodal Shift‑Work Intervention Randomized Trial

Chronotype Clinical trial Drivers

The SHIFTPLAN project is a randomized controlled trial testing whether a multimodal program can improve the health and performance of public transport drivers working shifts in Belgium. About 160 drivers were randomly assigned to either receive the program or stay on a waiting list. The intervention includes healthier scheduling practices (such as limiting quick returns and adapting rotations to workers’ chronotypes), a tailored education program on sleep and coping strategies, and an information campaign for shift planners. Researchers are measuring outcomes like fatigue, sleepiness, sleep quality, absenteeism, and general health at 3 and 6 months. While results are not yet available, this is the first large study to test a combined approach to managing shift-work challenges.

Shift Work Characteristics and Burnout Among Nurses

Burnout Cross-sectional Fatigue

This cross-sectional survey gathered responses from 873 nurses in the UK and Ireland in 2019 to examine how shift characteristics influence burnout and exhaustion. Participants reported on shift length, schedule choice, staffing levels, and break-taking. The study found that nurses working 12-hour shifts were more likely to report burnout, but this effect seemed linked to having less choice over their schedules. Inadequate staffing was another strong predictor of burnout. For exhaustion, rarely or never taking breaks also made symptoms worse. Overall, the results suggest that burnout is shaped not just by how long shifts are, but by how much control and recovery time staff have.

Shift Work and GERD: Systematic Review and Meta‑analysis

Circadian Digestive health Epidemiology

This meta-analysis reviewed 4 observational studies that compared digestive health in shift workers and day workers. In all studies, gastroesophageal reflux disease (GERD) symptoms were assessed with questionnaires. When the results were combined, shift workers were more likely to report reflux symptoms than day workers. The association was strongest for rotating shifts, but night shifts also showed elevated risk. The pattern appeared in both male-only and mixed-gender study groups, suggesting the effect applies broadly across worker populations.

Shift Work and Health Outcomes: Umbrella Review of Systematic Reviews

Cancer Cardiometabolic Cardiovascular

This umbrella review examined 8 systematic reviews and meta-analyses published up to 2020, covering 16 different health outcomes related to shift work. By bringing together results from thousands of workers across multiple studies, the review evaluated which links were strongest and most reliable. The clearest evidence showed that shift work increases the risk of heart attack and type 2 diabetes, especially with longer years of night-shift exposure. Evidence for other outcomes, such as prostate and colorectal cancer, was weaker and less consistent. Overall, the findings suggest that while shift work may affect many aspects of health, the most convincing risks are for long-term heart and metabolic disease.

Shift Work and Risk for Metabolic Syndrome Among Healthcare Workers

Cardiometabolic Cardiovascular Chronic disease

This systematic review and meta-analysis examined 12 studies of healthcare workers published up to 2021, comparing day staff with those on night or rotating shifts. Across samples ranging from 42 to 738 participants, most studies found that shift workers were more likely to meet the criteria for metabolic syndrome — a cluster of conditions including high blood pressure, elevated blood sugar, unhealthy cholesterol levels, and excess abdominal fat. When results were combined, shift workers were more than twice as likely to have metabolic syndrome compared to day workers.

Shift and Night Work and Mortality: Prospective Cohort Study

Cancer Cardiometabolic Chronic disease

This prospective cohort study followed over 1.5 million French employees from 1976 to 2002 using employment records and a job-exposure matrix to classify shift and night work. Mortality was tracked through the national registry, covering both overall deaths and specific causes. Over the 26 years of follow-up, more than 22,000 deaths occurred. The study found that shift and night workers had higher risks of all-cause mortality and several cause-specific deaths. In men, these included cardiovascular disease, cancer, smoking-related illness, and suicide. In women, shift work was associated with all-cause, cancer, and preventable mortality, with additional risks for suicide and breast cancer after long-term night work. The results showed dose–response patterns, meaning risks increased with more years of night-shift exposure.

Shift work is significantly and positively associated with possible gastro-esophageal reflux disease: A meta-analysis study

Circadian Digestive health Epidemiology

This meta-analysis reviewed 4 observational studies that compared reflux symptoms in shift workers and day workers. All studies relied on questionnaires to measure possible gastro-esophageal reflux disease (GERD). When combined, the results showed that shift workers were more likely to report GERD symptoms than day workers. Rotating shifts showed the strongest association, followed by permanent night shifts. The pattern appeared across both male-only groups and mixed-gender groups, suggesting the link applies broadly.

Shift‑Work Schedule Intervention for Extending Restart Breaks after Consecutive Night Shifts: a 5‑month study in nurses

Cross-sectional Education & training Fatigue

This 5-month study in a Japanese hospital tested a simple schedule change for 30 nurses: after two night shifts in a row, add one extra day off so the recovery break stretched from about 31 hours to about 55 hours. Nurses completed sleep diaries and short wellbeing surveys, and the team also tracked work hours plus simple tests of alertness, stress, and sleep using sensors under the mattress. With the longer break, nurses got more chances to sleep between the last night and the next shift and reported feeling less exhausted and less stressed, and they rated the new schedule as better for fatigue, sleepiness, and sleep quality. The objective tests did not show clear changes in alertness, sensor-measured sleep quality, or stress markers, and total work hours and days off didn’t increase overall.

Sleep and work functioning in nurses undertaking inpatient shifts in a blue‑depleted light environment

Blue-depleted Circadian Fatigue & alertness

This study followed 25 nurses at a Norwegian hospital to see how working in a blue-depleted light environment (warmer light with less blue spectrum at night) compared with standard hospital lighting. Over two weeks in each setting, nurses wore activity trackers, kept sleep diaries, and rated their mood, stress, sleepiness, and caffeine use. The results showed very few differences: nurses felt slightly sleepier during evening shifts under blue-depleted light, while they drank a bit more caffeine during night shifts under standard lighting. Otherwise, there were no meaningful changes in sleep length or quality, stress levels, or mood. Nurses did report that the blue-depleted light felt warmer and more relaxing, but overall their sleep and functioning were about the same in both environments.

A validation study of a commercial wearable (WHOOP) against polysomnography

Actigraphy Clinical Fatigue & alertness

This validation study tested the accuracy of the WHOOP wristband, a commercial sleep tracker, against polysomnography (the gold standard lab test for sleep) and actigraphy. Six healthy adults wore the WHOOP across nine nights while their sleep was measured in a lab. The device was found to be quite accurate at detecting overall sleep versus wake time, performing similarly to actigraphy for estimating total sleep duration and bedtime/wake time. However, when breaking sleep into stages (light, deep, REM), WHOOP was much less precise—sometimes underestimating or overestimating specific stages compared to the lab results. Overall, the device works well for tracking how long you sleep but is less reliable for detailed sleep stage breakdowns.

Association between shift work and sleep apnea: systematic review & meta‑analysis

Chronic disease Circadian Clinical

This systematic review and meta-analysis pulled together six workplace studies to examine whether shift workers are more likely to develop obstructive sleep apnea (OSA), a condition where breathing repeatedly stops during sleep. Five of the studies were combined for analysis, covering both healthcare and non-healthcare employees. The results showed only a very small, non-significant increase in OSA among shift workers compared with day workers. The evidence base was limited and inconsistent, as different studies used different methods to assess OSA, so the connection remains unclear.

Bright Light Treatment During Three Consecutive Night Shifts: Mixed Results in Nurses

Circadian Clinical trial Fatigue & alertness

This crossover study tested whether timed bright light could reduce sleepiness in 35 hospital nurses working three consecutive night shifts. Each nurse experienced both conditions: 30 minutes of bright light (10,000 lux) and 30 minutes of red dim light (placebo) scheduled between 2–3 a.m. on the first night shift and delayed by one hour on each subsequent night. Researchers tracked both subjective sleepiness (daily ratings and the Karolinska Sleepiness Scale) and objective alertness (Psychomotor Vigilance Task). Results showed that bright light modestly reduced reports of “heavy eyelids” during night shifts but had no significant impact on other measures of alertness or on recovery once the night shifts ended.

Evening Blue‑Depleted Light Environment in Hospitals and Nonvisual Effects

Blue-depleted Circadian Endocrine & hormones

This randomized crossover trial tested whether changing hospital evening lighting to a blue-depleted spectrum (warmer light with less blue wavelength) would better support circadian health. Twelve healthy adults stayed for five days in each lighting condition: standard hospital lighting and the blue-depleted system. Compared with standard lighting, the blue-depleted environment caused less melatonin suppression, shifted melatonin onset earlier, and led to slightly longer total sleep time and more REM sleep. Participants also showed lower neurocognitive arousal, with no significant side effects reported.

Evening Blue‑Light Blocking Glasses: Randomized Crossover Trial

Actigraphy Blue-blocking Blue-blocking glasses

This randomized crossover trial tested whether wearing blue light–blocking glasses in the evening could improve sleep in 20 healthy adults. Participants alternated between one week of wearing blue-blocking lenses and one week of clear control lenses from 6 p.m. until bedtime. Results showed that the blue-blocking glasses modestly improved some subjective sleep measures, such as falling asleep slightly faster and waking up fewer times during the night. However, objective sleep data from actigraphy did not show meaningful improvements, and total sleep time was even slightly shorter in the blue-blocking condition. Overall, the study suggests only limited benefits for healthy adults.

Non‑Pharmacological Interventions to Improve Chronic Disease Risk Factors and Sleep in Shift Workers: A Systematic Review and Meta‑Analysis

Blue-blocking Cardiometabolic Chrononutrition

This paper is a systematic review and meta-analysis of non-drug strategies to help shift workers sleep better and lower chronic disease risks. The authors searched seven databases and pulled together 65 real-world intervention studies (various jobs and schedules); 39 of those had enough data to pool across outcomes. Interventions fell into four buckets: schedule changes (e.g., forward rotation, longer recovery time, shorter “quick returns”), behavioral programs (sleep education, tailored coaching, activity and nutrition plans), controlled light exposure (timed bright light at work and/or blue-blocking for the commute and sleep), and a few complementary therapies (like massage). Across the pooled trials, objective sleep got better (people slept longer and spent a higher share of time actually asleep), while subjective sleep (how sleep felt) improved only a little. Health markers saw small, mixed gains: some studies showed modest drops in blood pressure or body weight, especially when programs targeted diet/activity or added more recovery time between shifts. Results varied a lot by job type and study quality, so there isn’t a single “best” fix—but several approaches showed repeatable, practical benefits.

Safety Incidents Associated with Extended Working Hours: Meta‑analysis

Epidemiology Evidence review Extended shifts / Overtime

This systematic review and meta-analysis examined whether extended working hours are linked to safety incidents (accidents, near-misses, and injuries) across multiple industries. The authors searched five databases through December 2020, screened 10,072 records, and synthesized 22 eligible studies. Across the pooled evidence, working more than 12 hours in a day and exceeding about 55 hours in a week were each associated with a higher risk of safety incidents. In contrast, smaller increases in daily or weekly hours did not show a consistent association. The authors rated the overall certainty of the evidence as low, noting the need for higher-quality studies, but the pattern for the longest hours was consistent enough to warrant attention.

Scheduled naps on the night shift: effects on drowsiness and nursing care quality

Fatigue Fatigue & alertness Field

This study tested whether giving nurses a chance to take a 30-minute scheduled nap during their 12-hour shifts would reduce fatigue and improve care. Thirty-eight nurses from two pediatric intensive care units kept work diaries before and after the nap program. A smaller group also wore devices that tracked eye activity to measure drowsiness. Results showed that nurses who actually took the naps reported less fatigue and better quality of care on some shifts, while those who skipped naps saw no improvement. Objective measures also showed a drop in high-risk drowsiness levels during shifts.

Shift and Night Work During Pregnancy and Preterm Birth—Cohort Study

Chronic exposure Circadian Cohort

This large Swedish cohort study followed nearly 5,000 pregnant healthcare workers to see how night-shift schedules affected preterm birth risk. Researchers found that in the first trimester, women who frequently worked three or more consecutive night shifts or had quick returns after night work (less than 28 hours off) faced a significantly higher risk of preterm birth. Frequent long shifts (10+ hours) early in pregnancy also raised risk. In the third trimester, working more than 40 hours in a week was linked to a doubled risk. The use of detailed scheduling records allowed researchers to identify that it was not just night work itself, but specific patterns — like consecutive nights and short recovery time — that mattered most.

Shift rotation direction and sustained attention in nurses

Attention Circadian Epidemiology

This cohort study followed 144 Italian nurses to compare how forward-rotating schedules (morning → afternoon → night) versus backward-rotating schedules (afternoon → morning → night) affected sleep and attention. Both schedules were linked to poor sleep quality overall, but backward rotations were clearly worse: nurses reported higher levels of sleepiness and showed slower reaction times and more lapses on attention tests. Those on forward rotations performed better, and the advantage held even after accounting for age, years of employment, and baseline sleep quality.

Shift work and health outcomes: an umbrella review of systematic reviews and meta‑analyses

Cancer Cardiometabolic Cardiovascular

This umbrella review assessed systematic reviews and meta-analyses covering a wide range of health outcomes linked to shift work. The clearest evidence pointed to disrupted sleep, shorter sleep duration, and higher risk of metabolic conditions such as obesity, diabetes, and metabolic syndrome. Moderate evidence supported links with cardiovascular disease, particularly hypertension and coronary heart disease. Associations with cancer—most notably breast cancer—were identified but varied in strength across studies. Evidence for mental health, reproductive outcomes, and gastrointestinal disorders was more limited and inconsistent.

Sleep Problems and Commuting vs Workplace Accidents in Workers

Circadian Commute safety Epidemiology

This study analyzed national survey and registry data from nearly 3,000 Chilean workers to see whether sleep problems were linked to accidents at work or during commutes. The results showed that workers with shorter sleep times were significantly more likely to be involved in commuting accidents—whether as drivers, passengers, or pedestrians—than workplace accidents. In fact, sleep quantity explained nearly a quarter of the variation in commuting accident rates. By contrast, the link between sleep and workplace accidents was weaker.

Sleep‑scheduling strategies in hospital shiftworkers: a scoping review

Circadian Education & training Fatigue & alertness

This study surveyed 89 hospital staff working 12-hour day and night shifts to learn how they manage sleep around demanding schedules. Researchers found that most workers used multiple strategies to cope, often shaped by personal or family responsibilities. Some strategies — like staying on a night schedule (“Night Stay”) or gradually switching before night shifts (“Switch Sleeper-N”) — were linked to lower mid-shift sleepiness. Others, including partial adjustments (“Incomplete Shifters”) or approaches that restricted total sleep, were tied to poorer adaptation. Overall, the study shows that not all sleep-scheduling strategies are equal, and personal circumstances play a big role in which ones workers choose.

A Longitudinal Study on Quick Returns and Occupational Accidents in Nurses

Cohort Epidemiology Fatigue

This 2-year study tracked 1,692 Norwegian nurses to see how “quick returns” — having less than 11 hours between shifts — influenced workplace accidents. Nurses who increased the number of quick returns over time were more likely to report accidents, including harm to themselves, patients, or equipment. By contrast, nurses who reduced their quick returns had a lower risk of accidents. The findings show that even small changes in recovery time between shifts can affect safety outcomes on the job.

Evening Light Intervention Before Night Shifts: Reduced Fatigue and Errors

Circadian Errors & incidents Fatigue & alertness

This randomized controlled trial tested whether bright light exposure in the evening, before night shifts, could help nurses working rotating schedules. Fifty-seven nurses were assigned to either an evening light + morning light avoidance plan or a diet-modification plan. Over 30 days, those in the evening light group made 67% fewer work errors, compared to only a 5% reduction in the diet group. The light group also reported less fatigue and a small boost in mood. Both groups experienced modest improvements in fatigue, sleepiness, and sleep duration, but the evening light intervention had the clearest effect on error reduction and fatigue.

How Tired is Too Tired to Drive? Systematic Review

Circadian Commute safety Errors & incidents

This systematic review analyzed 61 studies on how prior sleep duration affects driving safety. The evidence shows clear thresholds: after 6–7 hours of sleep, drivers already face about a 30% higher crash risk compared with being fully rested (≥8 hours). With only 4–5 hours of sleep, driving performance drops sharply and crash risk nearly doubles. Below 5 hours, the risk is consistently high. These findings support the idea that fatigue could be treated like alcohol, with a minimum “sleep requirement” for safe driving.

Light‑Emitting Blue‑Enriched Glasses During Early‑Morning Night‑Shift Hours: Field Study

Blue-blocking Blue-blocking glasses Blue-enriched

This field study tested whether blue-enriched light–emitting glasses could reduce fatigue and improve performance during the toughest part of a night shift—the early morning hours. Twenty-one shift workers used either blue-light glasses or dim red light glasses from 5:00–5:30 a.m. While sleepiness naturally increased across the night, the blue-light glasses did not significantly improve alertness or attention compared with the red-light control. However, participants rated the blue-light glasses as comfortable and reported no side effects, showing that wearable light devices can be used safely and conveniently in real work settings.

Night Shift Work Characteristics and Incident Coronary Heart Disease

Cardiometabolic Cardiovascular Circadian

This national cohort study followed more than 250,000 Danish healthcare workers, comparing night-shift employees with daytime workers to see if schedule details affected the risk of coronary heart disease (CHD). Men working night shifts had a modestly higher risk of CHD (22% higher), while the risk for women was slightly raised but not statistically strong. Importantly, the study found no consistent evidence that specific shift features—such as the number of monthly nights, consecutive nights, or years of night work—changed the risk. In this group, the overall exposure to night work, rather than the fine details of scheduling, appeared linked to heart health.

Night and Shift‑Work Patterns and Next‑Year Type 2 Diabetes Incidence

Cardiometabolic Chrononutrition Circadian

This large Swedish cohort study tracked nearly 28,000 nurses and nursing assistants to see how shift patterns influenced the risk of type 2 diabetes (T2D) and hypertension. Over several years, workers on permanent night shifts or with intensive schedules (more than 120 evening/night shifts in a year) had a significantly higher risk of developing T2D compared with day workers. The risk also tended to rise with more years of exclusive night work or frequent stretches of three or more consecutive night shifts. In contrast, night and shift work patterns were not linked to hypertension in this group.

PERCLOS‑Based Drowsiness Detection: Relevance to Post‑Night‑Shift Driving

Cognitive performance Commute safety Digital health

This narrative review looked at PERCLOS (the percentage of time your eyes are mostly closed) as a way to detect drowsiness. Research shows PERCLOS rises with sleep loss, sleep restriction, and during nighttime hours, making it one of the most validated measures of fatigue across lab studies, driving simulators, and real driving. Still, it isn’t perfect—PERCLOS can miss moderate drowsiness, may be less reliable in certain groups (like older adults), and definitions vary across devices. The review recommends further standardization and combining PERCLOS with other signals (like blinks or brain activity) to improve accuracy in real-world use.

Pros and Cons of Quick Returns: Nurses’ Perspectives

Cross-sectional Errors & incidents Fatigue & alertness

This cross-sectional survey of 96 Swedish nurses and nurse assistants examined experiences with quick returns (less than 11 hours of rest between evening and day shifts). The majority reported negative effects, including difficulty unwinding before sleep (76%), insufficient sleep (80%), and daytime fatigue (72%). About one-third (33%) perceived an increased risk of errors. However, participants also noted potential advantages: handover and planning the next day’s work were more often rated as easier after a quick return than after other shift sequences. Tolerance varied considerably, with some respondents reporting no ability to work quick returns without negative effects, while others indicated they could manage several per month.

Recovery from shift work: what is the evidence?

Chrononutrition Circadian Evidence review

This review examined how shift workers recover from the physical, mental, and social strain of irregular schedules. Research shows that recovery is influenced by many factors, including sleep timing, naps, caffeine or other stimulants, melatonin, light exposure, diet, exercise, and psychotherapy. Work schedules and social support also play an important role in how quickly workers can restore alertness and wellbeing. Evidence suggests that recovery often takes more than one day off, especially after several consecutive night shifts, and the effectiveness of recovery strategies varies by individual and schedule type.

Shift Work Hazards (StatPearls)

Burnout Cancer Cardiometabolic

This StatPearls entry reviews the health and safety hazards linked to shift work. It describes how irregular schedules contribute to insomnia, excessive sleepiness, and increased risk of workplace accidents and drowsy driving. Long-term associations include cardiovascular disease, metabolic syndrome, obesity, diabetes, gastrointestinal disorders, some cancers, and mental health concerns such as depression, anxiety, and burnout. The article also outlines the diagnostic criteria for Shift Work Disorder and discusses mitigation strategies, including sleep hygiene, controlled light exposure, naps, melatonin, wake-promoting agents, and adjustments to shift scheduling.

Shift Work and Metabolic Syndrome Updates: Systematic Review

Cardiometabolic Circadian Evidence review

This systematic review synthesized 16 recent studies on the relationship between shift work and metabolic syndrome (MetS). Evidence showed that circadian misalignment from night and rotating schedules disrupts multiple metabolic pathways, including glucose regulation, insulin function, cortisol timing, cholesterol balance, and melatonin secretion. These changes were associated with higher rates of abdominal obesity, dyslipidemia, impaired glycemic control, and hypertension—core components of MetS. The risk was greater with longer duration of night-shift exposure, while some findings suggested partial reversibility when shift work was discontinued.

Sleep Quality and Depression Symptoms Among Nurses Working Night Shifts (Saudi Arabia)

Cross-sectional Fatigue & alertness Healthcare workers

This cross-sectional study surveyed 191 nurses in Saudi Arabia to explore how night-shift work relates to sleep quality and depressive symptoms. Nurses working night shifts reported significantly poorer sleep quality on the Pittsburgh Sleep Quality Index (PSQI) compared with day-shift nurses. They also showed higher scores on the Hospital Anxiety and Depression Scale (HADS), indicating more depressive symptoms. Analysis revealed that both longer work hours and inadequate sleep were independently linked to higher rates of depressive symptoms among the nurses.

The Impact of 12‑h Night Shifts on Nurses’ Driving Safety

Commute Commute safety Fatigue & alertness

This study compared driving performance in 44 day-shift nurses and 49 night-shift nurses, using a simulator to measure safety after three consecutive 12-hour shifts and again after 72 hours off work. Results showed that nurses finishing night shifts had significantly more lane deviation during the simulated drive home compared to those finishing day shifts. This lane deviation is a recognized marker of higher collision risk, suggesting that fatigue from consecutive night shifts impairs post-shift driving safety.

The Relationship between Working Night Shifts and Depression in Nurses: Systematic Review and Meta-analysis

Circadian Evidence review Fatigue & alertness

This paper looked across many studies on nurses to see if working night shifts is linked to depression. When the authors combined the best-matched studies, night-shift nurses were more likely to have depressive symptoms than day-shift nurses. The reviewers point to two main reasons: night work disrupts normal sleep and throws off the body clock. The overall confidence in the evidence was judged as moderate. The review shows a clear pattern of risk, but it does not prove that night shifts directly cause depression.

Twelve‑Hour Night Shifts and Nurses’ Driving Safety: Simulator Study

Commute Commute safety Fatigue & alertness

This high-fidelity simulator study tested driving performance in nurses after completing three consecutive 12-hour shifts, comparing day-shift and night-shift conditions. After night shifts, nurses showed more lane drifting, slower reaction times, and reduced driving stability compared with their performance after day shifts. The findings suggest that extended night schedules can temporarily impair alertness behind the wheel, even in experienced healthcare professionals.

Two‑Nap Strategy in Simulated Night Work (90‑min + 30‑min) vs One 120‑min Nap

Fatigue Fatigue & alertness Field study

Researchers ran a 16-hour simulated night shift and compared three options: no nap, one 120-minute nap from 22:00–00:00, or two naps (90 minutes from 22:30–00:00 and 30 minutes from 02:30–03:00). The split-nap plan led to less drowsiness (until ~06:00) and less fatigue (until ~09:00) than no nap or one long nap. However, neither nap plan improved morning performance on their thinking task; some people also felt groggy right after napping, especially after longer or poorly timed sleep. These results come from a small lab study in non-shift-working young women, so real-world effects may differ.

A Shift to Something Better? Work Schedule Change and Sleep Medication Use

Cohort General population Health outcomes

This long-term study followed over 2,000 Norwegian nurses to see how changes in work schedules affected the use of prescription sleep medications. Nurses who moved from night shifts to day-only work were more than 50% less likely to use sleep medication compared with those who continued night work. Nurses who switched to shifts without nights also showed a reduction, though the results were not statistically significant. The findings suggest that leaving night work may improve sleep enough to reduce reliance on sleep aids.

Association Between Shift Work and Reflux Esophagitis (Endoscopy‑Based)

Age & aging Circadian Cohort

This large cohort study in South Korea followed more than 140,000 adults between 2012 and 2018 to examine whether shift work increases the risk of reflux esophagitis, a condition where stomach acid damages the esophagus. Using endoscopy, researchers confirmed over 35,000 new cases. Shift workers had a modest but significant increase in risk compared with day workers, particularly among younger adults and women. Rotating shifts were more strongly linked to reflux than fixed shifts, suggesting that irregular hours may worsen digestive health.

Data‑Driven Working‑Hour Patterns and Accident Risk

Cohort Epidemiology Fatigue & alertness

This cohort study tracked over 4,400 hospital employees in Finland between 2008 and 2018, linking payroll data on working hours with national accident records. Researchers used cluster analysis to identify six weekly work-hour patterns. Employees whose weeks included long shifts (over 12 hours), late-night work, and “quick returns” with less than 11 hours between shifts had a higher risk of occupational accidents. Compared with the lowest-risk schedules, the riskiest patterns increased accident risk by about 30%.

Feasibility of Time‑Restricted Eating and Impacts on Cardiometabolic Health in Firefighters on 24‑h Shifts

Cardiometabolic Chrononutrition Clinical

This randomized controlled trial tested whether a 10-hour time-restricted eating (TRE) schedule was realistic and beneficial for 137 firefighters working 24-hour shifts. Over 12 weeks, the TRE group successfully reduced their eating window from about 14 hours to 11 hours without adverse effects. Compared with standard care, TRE improved quality of life scores and reduced very low-density lipoprotein (VLDL) particle size. Among firefighters who started with elevated health risks, TRE also lowered HbA1c and diastolic blood pressure. The results show that TRE is both feasible and helpful in improving certain markers of metabolic health for people in demanding shift-based jobs.

Impact of Light Therapy on Rotating Night‑Shift Workers

Circadian Clinical Endocrine & hormones

This randomized trial studied whether bright-light therapy could improve health in 22 rotating night-shift workers. Participants received daily 30-minute sessions of white light for 12 weeks, followed by 12 weeks off. Light therapy did not improve glucose tolerance, inflammation, sleep quality, or other metabolic measures. However, it did alter circadian clock gene activity in blood cells, including reduced REV-ERBα expression and shifts in the REV-ERBα/BMAL1 ratio. These changes suggest that while light exposure influences biological rhythms at a molecular level, it did not translate into short-term health improvements in this study.

Influence of Shift Work on the Health of Nursing Professionals

Burnout Cross-sectional Fatigue & alertness

This observational study surveyed 380 nurses from several Spanish cities between March and May 2019 to compare the health effects of fixed versus rotating shifts. Participants completed validated questionnaires measuring gastrointestinal symptoms, stool consistency, anxiety, depression, stress, sleep quality, and perceptions of their work environment. Results showed that nurses on rotating shifts reported more abdominal pain, worse sleep efficiency, higher anxiety and depression scores, and more symptoms of depersonalization. They also rated their work environment more negatively. The findings suggest that rotating shift schedules may directly contribute to digestive issues, emotional strain, and reduced quality of care.

Irritable Bowel Syndrome and Shift Work: Meta‑analysis

Circadian Digestive health Epidemiology

This meta-analysis reviewed 8 observational studies published up to mid-2021 to test whether shift work is linked to gastrointestinal disorders. Across the combined data, shift workers were 81% more likely to have irritable bowel syndrome (IBS) than non-shift workers. The analysis showed very low heterogeneity, adding confidence to the result. By contrast, there was no significant association between shift work and functional dyspepsia (FD). The findings suggest that shift work is a likely risk factor for IBS, but not for FD.

Lighting Interventions and Sleepiness in Night‑Shift Workers: Meta‑analysis

Blue-blocking / Blue-depleted Circadian Evidence review

This systematic review and meta-analysis evaluated 14 intervention studies from 7 countries to test whether lighting strategies reduce sleepiness in night-shift workers. Researchers pooled results across trials that compared standard lighting with alternatives such as bright light and blue-enriched light. Overall, lighting interventions significantly reduced self-reported sleepiness, with the strongest effects seen for blue-enriched white light above 5000 Kelvin. These findings provide consistent evidence that tailored lighting can help night-shift workers feel less drowsy during overnight hours.

Metabolic Syndrome Risk Among Health‑Sector Shift Workers: Systematic Review

Cardiometabolic Chronic disease Circadian

This systematic review pulled together results from 12 studies of healthcare workers published before 2021. The studies compared nurses, doctors, and other staff working day shifts with those on night or rotating shifts. Researchers looked at the rates of metabolic syndrome — a cluster of conditions including high blood pressure, high blood sugar, excess body fat, and abnormal cholesterol. Across nearly all of the studies, shift workers were more than twice as likely to have metabolic syndrome compared to day workers. While the exact risks varied from study to study, the overall trend was clear: irregular schedules were strongly tied to poorer metabolic health in healthcare staff.

Night/Shift Work and Cerebrovascular Disease: Systematic Review/Meta‑analysis

Cardiometabolic Chronic disease Circadian

This prospective cohort study followed over 30,000 nurses and nursing assistants in Stockholm between 2009 and 2017 to examine whether night and shift work raised the risk of cerebrovascular disease (such as stroke). Work schedules were tracked through payroll records, allowing researchers to measure the number of night shifts, consecutive night shifts, and recovery time between shifts. During follow-up, 223 new cases of cerebrovascular disease were recorded. The risk was higher in employees who worked more than 30 night shifts per year, had frequent stretches of three or more consecutive nights, or had limited recovery time between shifts. Nurses with more than five years of night-shift exposure also showed increased risk.

Night Shift Work and Myocardial Infarction in the UK Biobank

Age & aging Cardiometabolic Cardiovascular

This large UK Biobank study followed workers for about 12 years to examine night-shift schedules and myocardial infarction (heart attack). Compared with day workers, those doing occasional or some night shifts had a modestly higher chance of heart attack (about 9–13% higher). The elevation was greater for permanent night shifts (about 21% higher). Risk also tended to rise with time on nights (roughly 20% higher for under 10 years and about 50% higher for 10 years or more) and with frequency (more than 8 night shifts per month was about 45% higher). Among night-shift workers, having more rest days between shifts did not show a difference compared with one rest day. This was an observational study, so it identifies associations rather than proving cause.

Night shift work and breast cancer risk (review)

Age & aging Breast cancer Cancer

This evidence update reviewed six cohort and four case-control studies published since 2019 on night shift work and breast cancer. Taken together, the new studies provide some support that breast cancer risk may be higher with many years or high frequency of night shifts, but results are not consistent and many studies were small. The update did notadd clear answers about whether risk differs by menopausal status, chronotype (morning/evening preference), tumor hormone subtype, or genetic factors. Overall, the authors conclude the new data somewhat strengthen the earlier evidence but better, longer-term studies with precise exposure measures are still needed.

Night shift work and female breast cancer: a two‑stage dose–response meta‑analysis

Age & aging Breast cancer Cancer

This meta-analysis combined results from 10 cohort studies and 11 case-control studies, involving more than 15,000 breast cancer cases. The researchers focused on how many years women had worked night shifts, instead of just comparing “ever vs. never” night work. They found that breast cancer risk increased gradually with longer night-shift exposure. In cohort studies, the risk rose about 4% after 10 years and 13% after 30 years. In case-control studies, the risk estimates were higher, showing about a 23% increase after 10 years and nearly 88% after 30 years. Overall, the study strengthens the evidence that the length of night-shift work matters when evaluating breast cancer risk.

Night‑Shift Status During Pregnancy and Small‑for‑Gestational‑Age Risk

Age & aging Birth outcomes Circadian

This South Korean birth-cohort study followed nearly 5,000 pregnant women and compared birth outcomes based on work schedules: not working, daytime jobs, shift work without nights, and night work. Overall, working during pregnancy did not raise the risk of preterm birth or babies being small for their gestational age (SGA). However, among the small group of women who worked night shifts during pregnancy (just 34 women in total), the risk of having an SGA baby was higher compared with women who were not working. Night work was not linked to preterm birth. Because so few women in the study worked nights, the results should be read as a warning sign rather than a definite conclusion.

Occupational Risk for Coronary Artery Disease in Shift Workers: Review

Cardiometabolic Cardiovascular Circadian

This systematic review analyzed 15 studies published between 2013 and 2023 on shift work and coronary artery disease (CAD). Most studies assessed risk, with one looking at management. Overall, shift workers were found to have a higher risk of CAD compared to non-shift workers. Longer duration of shift work was linked with greater risk, and some studies showed more coronary artery plaques in workers with many years of night or rotating shifts. The review notes that while the exact biological mechanisms are not fully clear, circadian rhythm disruption, stress, and metabolic changes are thought to contribute. The authors conclude that evidence is strong enough to support creating occupational guidelines to reduce CAD risk in shift workers.

Shifting Rhythms: Systematic Review of Night Shift Work and Cardiovascular Biomarkers

Atherosclerosis Biomarkers Cardiometabolic

This systematic review examined 14 studies published over the past decade, including systematic reviews, cohort studies, and cross-sectional research, to explore how shift work affects cardiovascular health. The evidence consistently showed that people working night or rotating shifts face higher risks of conditions such as coronary heart disease, myocardial infarction, hypertension, atherosclerosis, and metabolic syndrome. These risks tended to rise with longer years or higher frequency of night-shift exposure. Alongside these clinical outcomes, studies also found biological changes — such as higher blood pressure, impaired glucose control, abnormal cholesterol patterns, and increased inflammatory or oxidative stress markers — that help explain why shift work may strain the cardiovascular system.

Shiftwork and Insulin Resistance in Professional Drivers

Cardiometabolic Chrononutrition Circadian

This study looked at almost 400 male drivers in Egypt to see whether working night shifts was linked to problems with how the body handles blood sugar. Compared to drivers who worked daytime hours, night-shift drivers showed stronger signs of insulin resistance — a condition where the body has a harder time using insulin effectively, and an early warning sign for type 2 diabetes. The risks were even higher for night-shift drivers who also had trouble sleeping or irregular eating habits, such as skipping breakfast or eating late at night. While the study can’t prove cause and effect, it highlights how disrupted schedules, poor sleep, and off-timed meals may combine to strain the body’s metabolism.

Sleep Regularity is a Stronger Predictor of Mortality than Sleep Duration

Behavioral health Cardiometabolic Circadian

This large study used data from nearly 61,000 adults in the UK Biobank who wore activity monitors for one week to measure how consistent their sleep patterns were. Researchers tracked deaths over the following years and found that people with the most regular sleep schedules had about a 30% lower risk of dying from any cause compared to those with the most irregular schedules. Sleep regularity also predicted deaths from heart and metabolic diseases. While total sleep duration was still important, regularity was an even stronger predictor of long-term survival. These findings suggest that the stability of sleep timing — going to bed and waking up around the same times each day — may be a key factor in long-term health.

Sleep, mental health and physical health in new shift workers: longitudinal study

Adaptation Adjustment Behavioral health

This review pulled together 48 studies that followed people as they began shift work. Across those studies, the first effects showed up in sleep and mental health: people slept less and reported more symptoms like low mood, stress, and burnout within the first months. By contrast, most physical health measures didn’t show clear changes that early, although some studies did find more fatigue and worse self-rated physical health. The review also found that how someone was doing before they started—especially their sleep and mental health, plus aspects of the job schedule—helped predict who coped better once shifts began. Overall, the evidence points to the transition period as a vulnerable time where problems tend to start.

The Effects of Fasting vs Meal or Snack During Simulated Night Work

Cardiometabolic Chrononutrition Circadian

This article is a protocol for a randomized, laboratory-based study that will test how night-time eating patterns influence metabolic responses during simulated night shifts. Healthy adults will complete a seven-day in-lab schedule (daytime sleep, night-time wake) and be randomized to one of three conditions: a full meal at night, a small night-time snack, or no night-time eating with calories redistributed to daytime. Diet composition and total daily energy will be tightly controlled. The primary outcomes are next-morning glucose, insulin, and free-fatty-acid responses assessed via an oral glucose tolerance test; secondary outcomes include cognitive performance, driving simulation, polysomnography-based sleep measures, mood, and circadian hormones. This paper outlines methods only and does not report results.

The effects of time‑restricted eating on sleep in adults: a systematic review

Behavioral health Chrononutrition Circadian

This systematic review analyzed six randomized controlled trials (≥14-hour daily fasting; 8–14 weeks) assessing time-restricted eating (TRE) and sleep in adults. Across studies using objective wearables and self-report tools, TRE was generally sleep-neutral: one trial reported fewer sleep disturbances, while others found small adverse changes on select outcomes (a shorter sleep duration in one study, lower sleep efficiency in two, and longer time to fall asleep in one). Overall, short- to mid-term TRE did not typically degrade sleep, but measurable effects—positive or negative—were inconsistent and appeared to depend on participant characteristics and the specific TRE schedule.

Two‑nap strategy in simulated night work: a 90‑min followed by a 30‑min nap maintains performance

Actigraphy Circadian Cognitive performance

This randomized, crossover pilot (12 healthy young women in a simulated night-work setting) compared two planned nap sequences—90 minutes then 30 minutes (ending ~00:00 and ~03:00) versus 30 minutes then 90 minutes (ending ~00:00 and ~04:00)—against no nap. Thirty-minute naps produced little sleep inertia, whereas 90-minute naps were followed by transient grogginess. Relative to no nap, both two-nap schedules were associated with less sleepiness and fatigue and with better psychomotor vigilance 1–2 hours after napping and through the early morning. The 90-then-30 pattern more clearly reduced subjective fatigue and shortened reaction times, while the 30-then-90 pattern better preserved early-morning cognitive performance despite brief inertia immediately upon waking from the longer nap. Findings rely on actigraphy and standardized vigilance/mental-arithmetic tasks, and generalizability is limited by the small, homogeneous sample and simulated environment.

Adapting shift work schedules for sleep quality, sleep duration, and sleepiness in shift workers (Cochrane Review)

Adjustment Evidence review Fatigue & alertness

This Cochrane review analyzed 11 studies with more than 2,000 shift workers to see how schedule changes affect sleep and alertness. The results showed mixed and often uncertain effects. Forward-rotating schedules (day → evening → night) and faster rotations may reduce sleepiness during shifts, but the evidence is weak, and faster rotations also shortened total sleep time. The most clear finding came from studies limiting maximum shift length to 16 hours, which gave workers about 45 minutes more sleep per day and slightly reduced on-shift sleepiness. Other changes, like shorter shifts or compressed workweeks, showed no consistent benefits. Overall, scheduling tweaks can influence fatigue, but the evidence remains limited and more high-quality research is needed.

Association between night shift work and non‑alcoholic fatty liver disease (NAFLD): UK Biobank cohort

Cardiometabolic Circadian Cohort

This study followed more than 280,000 adults in the UK Biobank for about 12 years to see if night-shift work was linked to non-alcoholic fatty liver disease (NAFLD). Researchers found that people who worked permanent night shifts were about 27% more likely to develop NAFLD compared with those who rarely or never worked nights. The risk was even higher for people with more years on night shifts, more shifts per month, longer than 12-hour shifts, or several nights in a row. Part of the link was explained by weight gain, but the increased risk was seen even after adjusting for lifestyle and health factors. Genetic risk didn’t change the results, suggesting that night-shift work itself plays a role.

Blue‑light filtering spectacle lenses for visual performance, sleep, and macular health in adults (Cochrane Review)

Blue-blocking Blue-blocking glasses Circadian

This Cochrane review looked at 17 clinical trials that tested whether blue-light filtering glasses improve eye comfort, sleep, or protect eye health. The studies included over 600 adults and followed them for periods ranging from less than a day to five weeks. Results showed little to no short-term benefit for reducing digital eye strain or improving vision compared with regular lenses. The effect on sleep was uncertain, with some trials reporting small improvements and others showing no difference. Importantly, none of the studies provided evidence on whether these glasses protect the back of the eye (macula) or improve long-term eye health. Reported side effects were rare and mild, such as headaches or discomfort wearing the glasses. Overall, the evidence suggests that blue-light glasses are safe but offer limited short-term benefits, and more high-quality research is needed to know their long-term effects.

Circadian Alignment of Food Intake and Glycaemic Control by Time‑Restricted Eating: Meta‑analysis

Cardiometabolic Chrononutrition Circadian

This review combined 18 controlled studies with 1,169 adults to test whether time-restricted eating (TRE) improves blood sugar control over 4 to 14 weeks. On average, TRE did not change fasting glucose across all studies. It did lower HbA1c and lower fasting insulin, and it nearly lowered HOMA-IR. Timing mattered. When eating windows were set earlier in the day (early TRE), fasting glucose did go down. When eating windows were later, that benefit faded. Most studies involved people with overweight or obesity, and only a few included diabetes. The findings suggest TRE can help some blood sugar measures in the short term, especially when meals are earlier, but effects are modest and depend on timing.

Circadian Misalignment Increases 24‑h Acylated Ghrelin in Chronic Shift Workers (Randomized Crossover)

Appetite regulation Chrononutrition Circadian

This small randomized crossover study tested seven healthy chronic night-shift workers in a lab for two 3-day conditions: a day-work (aligned) schedule and a night-work schedule with a 12-hour inversion (circadian misalignment). With diet kept constant, misalignment increased 24-hour acylated ghrelin by ~17%, a hormone that stimulates appetite. Participants also felt ~14% hungrier at “breakfast” on the misaligned schedule. Energy expenditure and respiratory exchange ratio didn’t change, meaning they didn’t burn more calories. Interestingly, overall activity was ~38% higher during misalignment even though sleepiness also increased. These are acute effects measured over a few days in a small sample, so the study does not prove long-term weight gain—but it shows that circadian misalignment can raise hunger signals in actual shift workers.

Consequences of Shift Work and Night Work: Literature Review

Absenteeism & presenteeism Cancer Cardiometabolic

This literature review looked at 129 studies published in 2019 on the effects of shift and night work. Most of the research (over 80%) focused on health problems, showing consistent links to sleep disruption, fatigue, mental health issues, cardiovascular strain, metabolic disorders, and even cancer risk. Far fewer studies looked at impacts on family life (7%) or the workplace (9%). The family-related studies pointed to conflict between work and home life, strained relationships, and negative effects on children’s well-being. Organizational studies highlighted concerns such as more errors and accidents, reduced performance, and absenteeism. Overall, the review shows that shift work affects not just health, but also home life and job sustainability—yet research still pays much less attention to the latter two areas.

Effect of Meal Glycemic Index and Meal Frequency on Glycemic Variability During Night Shifts

Cardiometabolic Chrononutrition Circadian

Summary This randomized cross-over study tested female nurses working real night shifts. Each nurse completed three 3-day periods (in random order) during nights: no meal, low-glycemic-index (low-GI) yogurt-based meal(s), or high-GI meal(s). Some nurses had one night-shift meal; others had three—so the study could separate meal frequency (1 vs 3) from meal type (low vs high GI). Continuous glucose monitors tracked blood sugar during the night shift (21:30–07:00), the following morning (07:00–13:00), and over 24 hours. What happened: - High-GI meals caused bigger spikes and more variability in blood sugar at night, the next morning, and often across 24 h, compared with no meal. - Low-GI meals were about the same as fasting on almost all stability measures (one small exception at night with three low-GI snacks). In some analyses, low-GI even looked better than fasting the next morning/over 24 h. - Meal frequency (1 vs 3) didn’t independently affect glucose control once GI was considered. Bottom line: At night, what you eat mattered more than how often you eat.

Effectiveness of Sleep Interventions for Rotating Night‑Shift Workers

CBT-I Circadian Evidence review

This systematic review and meta-analysis pulled together 30 studies (with 25 in the meta-analysis) on ways to improve sleep in rotating night-shift workers. Interventions included medications, light therapy, cognitive-behavioral approaches (e.g., CBT-I), aroma/alternative therapies, and shift-schedule modifications. Across studies, the overall effect on sleep was moderate (Hedges’ g = 0.59), meaning these strategies generally improved sleep or reduced sleep problems. However, results varied by intervention type and worker group, and not every approach worked the same way for everyone. The included trials ran from 1990 to June 2022 and used both randomized and quasi-experimental designs.

American Academy of Nursing Policy Recommendations to Reduce Health Risks of Night‑Shift Work

Age & aging AI & digital health Burnout

This American Academy of Nursing consensus paper synthesizes evidence that night-shift nursing is an occupational health hazard linked to higher risks of diabetes, cardiovascular disease, cancers, depression, cognitive impairment, and earlier mortality—and that these risks drive substantial costs via errors, burnout, turnover, and increased healthcare use. The paper stresses sex differences in shift tolerance and calls out health-equity gaps, then moves beyond individual fixes to system solutions: advocate legislation and regulation that create safe night-shift conditions; fund research to define safer shift designs and disease-prevention strategies; and engage insurers, organizations, and government to recognize and pay for prevention. Proposed initiatives include virtual nursing to redistribute workload, AI to cut medication errors and track burnout/well-being, circadian-savvy lighting (e.g., red-light alertness at night without suppressing melatonin), eliminating mandatory overtime, tracking errors by shift, and piloting alternative/staggered night schedules (shorter 4–6-hour blocks or revised 8-hour patterns) to protect sleep and cognition. Rather than prescribing fixed rules (e.g., a set limit on consecutive nights), the AAN issues three policy recommendations: (1) systemic changes that reduce circadian disruption and disease burden; (2) working conditions that respect nurses’ rights and improve safety/quality; and (3) advancing novel tech and scheduling models—backed by research funding and multi-stakeholder accountability.

Artificial Light at Night and Type 2 Diabetes: Review

Artificial light at night (ALAN) Cardiometabolic Circadian

This systematic review examines evidence linking artificial light at night (ALAN) to type 2 diabetes risk. Studies in both general and working populations show that higher nighttime light exposure—whether from outdoor sources, workplace lighting, or personal devices—is associated with disrupted sleep, circadian misalignment, and impaired glucose regulation. While study designs vary, the overall evidence suggests that reducing nighttime light exposure could play a role in lowering diabetes risk.

Association of Shift Work with TyG Index (Insulin Resistance) in Male Workers

BMI Cardiometabolic Cardiovascular

This cross-sectional study analyzed health records from over 3,000 male workers in a Korean chemical plant to see if shift work was linked to insulin resistance, using the triglyceride-glucose (TyG) index as a marker. Researchers compared day workers with night or rotating shift workers, focusing on whether workers had TyG values above 4.69, a level linked to higher diabetes risk. After adjusting for age, obesity, smoking, drinking, and other health factors, shift workers had about 22% higher odds of crossing this risk threshold. The findings suggest that shift work is associated with early metabolic changes that may raise the risk of developing type 2 diabetes.

Changing Organizational Work Schedules Reduces Quick Returns: Effects on Sleep and Fatigue

Circadian Fatigue Fatigue & alertness

This editorial reviews findings from a large randomized controlled trial that tested whether reducing “quick returns” — shifts separated by fewer than 11 hours — could improve workers’ sleep. The trial involved hospital employees and showed that when schedules were adjusted to allow longer rest periods between shifts, participants reported fewer insomnia symptoms and less daytime sleepiness. The effects were modest but meaningful, demonstrating that organizational-level changes to scheduling can improve sleep health, even without targeting workers with diagnosed sleep disorders.

Chrononutrition and health (Frontiers editorial)

Cardiometabolic Chrononutrition Circadian

This editorial introduces a special issue on chrononutrition, the study of how meal timing interacts with circadian rhythms and health. The featured articles cover a wide range of topics, including how evening chronotypes tend to have poorer diet and sleep habits, how time-restricted eating can improve markers of liver health, and how maternal night-time eating may affect infant growth. Other studies explored meal timing for blood sugar control and the potential role of intermittent fasting in chronic illness. Together, these findings highlight that not only what we eat, but also when we eat, can shape metabolic and overall health.

Chrono‑nutrition and sleep: systematic scoping review

Chrononutrition Chronotype Circadian

This systematic scoping review mapped 115 human studies on how when we eat relates to sleep. Across the literature, late eating is frequently associated with poorer sleep quality and continuity (for example, taking longer to fall asleep or waking more at night), while effects on sleep duration are mixed. Skipping breakfast is linked to later bedtimes and lower self-reported sleep quality (with shorter duration mainly in youth). Experiments that shift entire meal schedules earlier vs later often show no short-term change in sleep, and studies of time-restricted eating report mostly neutralsleep effects with occasional small improvements. Because studies differ in design, meal-to-bedtime timing, meal composition, and participant characteristics, the authors conclude that strong clinical guidance isn’t ready yet and call for more rigorous trials using objective sleep measures.

Circadian‑Informed Lighting Improves Vigilance and Sleep in Simulated Night Shifts

Alertness Blue-depleted Blue-enriched

This randomized, counterbalanced crossover lab study (19 adults) tested “circadian-informed” lighting—blue-enriched light during night work and blue-depleted light when appropriate—against a dim, blue-depleted control during four simulated night shifts with daytime sleep. Under the circadian-informed condition, participants showed about 50% fewer psychomotor vigilance (PVT) lapses by the end of the protocol, reported lower sleepiness (KSS) at mid-shift on days 6–7, and slept ~52 minutes longer during daytime sleep by day 7. Effects on other cognitive tasks were inconsistent. Overall, aligning light spectrum and intensity with circadian biology improved vigilance, reduced sleepiness, and increased daytime sleep in this simulated night-shift setting.

Cumulative Night Shift Work and Incident Cardiovascular Disease: Gutenberg Health Study

Age & aging Cardiometabolic Cardiovascular

This 5-year prospective analysis from the Gutenberg Health Study examined whether cumulative night-shift work over the prior 10 years relates to new cardiovascular disease (CVD) in 7,607 employed adults without CVD at baseline. Compared with day workers, night-shift workers had a higher crude CVD incidence (6.88 vs 5.19 per 1,000 person-years). After adjusting for age, sex, and job factors, hazard ratios for CVD were elevated but not statistically significantacross low, middle, and high exposure categories (e.g., HR 1.37 [0.74–2.53] for 1–3 years exposure). The authors interpret these as suggestive trends, emphasizing that longer follow-up and more events are needed to clarify the relationship.

Digital cognitive behavioural therapy for insomnia reduces insomnia in nurses with shift work disorder: a randomized controlled pilot trial

Anxiety CBT-I Circadian

This randomized pilot trial tested a guided digital CBT-I program adapted for shift work (“SleepCare”) in 46 nurses with shift-work disorder and insomnia. Compared with a waitlist control, the program produced a clinically meaningful drop in insomnia severity (primary outcome; β = −4.73; p<.001). Participants also reported improvements in daytime sleepiness, unhelpful sleep beliefs, cognitive arousal, and diary-based sleep (better sleep efficiency and faster sleep onset), plus lower depression/anxiety and better work ability; however, objective sleep (actigraphy) did not significantly change. Benefits in the treatment group were maintained at 6-month follow-up. Engagement and satisfaction were high.

Effect of a 2‑Hour On‑Shift Nap vs 30‑Minute or No‑Nap on Post‑Night‑Shift Performance

Alertness Circadian Clinical trial

This randomized crossover lab study compared three on-shift nap strategies during 12-hour simulated night shifts in mostly EMS clinicians: a 2-hour nap, a 30-minute nap, or no nap. The 2-hour nap, taken at 02:00, led to better vigilance (fewer PVT false starts at end of shift and start of recovery), and lower sleepiness and fatigue with some moodimprovements during the daytime recovery period, versus the other conditions. Importantly, night-shift nap length did not change subsequent recovery sleep (no differences in sleep during the recovery window).

Effects of Abated Quick Returns (<11 h) on Insomnia and Sleepiness

Circadian Fatigue Fatigue & alertness

This large cluster randomized trial in a Norwegian hospital tested cutting down “quick returns” (making sure there are >11 hours between shifts) for 6 months. Units assigned to the new schedule halved their quick returns (about 13.2 → 6.7), while control units stayed near 13.2 → 12.0. Compared with usual scheduling, the reduced–quick-return schedule led to small but significant improvements in insomnia symptoms and daytime sleepiness. There was no improvementin work-related fatigue.

Fasting Overnight During Simulated Night Shift Mitigates Glucose Impairment

Cardiometabolic Chrononutrition Circadian

This lab trial put healthy adults on four simulated night shifts and assigned them to one of three eating plans: no calories overnight (fast at night), small snacks at night, or full meals at night (everyone ate the same total calories overall). Night work made people’s bodies less sensitive to insulin across the board, but those who fasted at night had a much smaller rise in blood sugar after a glucose drink than those who ate or snacked overnight. They also showed signs that the body released insulin more effectively right after the drink. The study also tracked NEFA AUC—the total amount of “free fatty acids” floating in the blood during the test. NEFA totals went up when people ate or snacked at night, but not when they fasted, suggesting overnight eating pushed more fat into the bloodstream. No adverse events were reported.

Global prevalence of occupational injuries in iron and steel industries: a systematic review and meta‑analysis

Circadian Epidemiology Evidence review

This systematic review and meta-analysis pooled 15 studies from 9 countries on injuries in iron and steel workers. On average, about 55% of workers reported an occupational injury in the time frames studied (rates varied a lot by study). Two factors stood out: workers who did not use personal protective equipment (PPE) had about 4 times higher oddsof injury than those who did, and those working night shifts had about 65% higher odds of injury than workers who did not work nights.

Intra‑individual Study: Quick Returns, Sleepiness, and Restedness in Nurses

Actigraphy Anxiety Circadian

This within-person field study followed 90 nurses and assistant nurses who each experienced both an evening→day “quick return” (less than 11 hours between shifts) and a normal day→day schedule. Using actigraphy (a wrist-worn sleep tracker) plus daily diaries, quick returns were linked to about 1 hour less sleep, worse self-rated sleep quality, more sleepiness while at work, and more anxiety at bedtime the very next day. Objective sleep fragmentation (how broken up sleep was) and stress ratings did not differ between the two schedules.

Long‑Term Night Shift Work and Incident COPD Risk

Age & aging Cardiometabolic Circadian

This UK Biobank study followed 277,059 working adults for about 13 years to see whether long-term night-shift workwas linked to chronic obstructive pulmonary disease (COPD). Compared with day workers, people who rarely or sometimes worked nights had about a 28% higher risk of COPD, and those on permanent night shifts had about a 49% higher risk. Risk was higher with more years on nights (especially ≥10 years) and with more than 8 night shifts per month. The researchers also built a COPD-specific genetic risk score (GRS) and found an additive effect: people with permanent night shifts plus high genetic risk had about 90% higher risk than day workers with low genetic risk.

Night Shift Work Associates with All‑Cause and Cause‑Specific Mortality: UK Biobank

Age & aging Cardiometabolic Cardiovascular

This UK Biobank study followed 283,579 workers for a median of 14 years to see how night-shift schedules relate to death rates. Compared with day workers, shift workers overall had a 12% higher hazard of all-cause mortality. At baseline, the increase was seen in those with no/rare night shifts (~16% higher) and irregular night shifts (~9% higher). Looking at cumulative exposure, the pattern was non-linear: only people with 20–30 years of night-shift work had clearly higher hazards—about 52% higher for all-cause mortality and more than double for cardiovascular disease (CVD) mortality. (Observational study: shows associations, not proof of cause.)

Time‑restricted eating in shift workers: a systematic review and meta‑analysis

Cardiometabolic Chrononutrition Circadian

This systematic review and meta-analysis pooled results from small clinical trials testing time-restricted eating (TRE) in shift-working populations. Most interventions limited food intake to a fixed daily window of around 8–10 hours, often scheduled during the daytime. Across studies, TRE was associated with improved glucose regulation, reduced fasting insulin, and modest weight benefits compared with unrestricted eating. However, effects varied depending on study length and design, and the evidence base is still limited.

Associations Between Shift Work and Insulin Resistance Markers in >53,000 Workers (Spain)

Cardiometabolic Cardiovascular Circadian

This cross-sectional study analyzed health data from 53,053 employed adults in Spain, comparing day workers with night and rotating shift workers. Researchers calculated four validated markers of insulin resistance—TyG, TyG-BMI, METS-IR, and SPISE. Across all indices, shift workers showed significantly higher insulin resistance than day workers, with adjusted odds ratios ranging from 1.49 to 1.89. These associations persisted even after accounting for age, education, physical activity, and dietary patterns. Men consistently showed a higher insulin resistance burden than women.

Daytime Eating During Simulated Night Work Mitigates Cardiometabolic Changes

Cardiometabolic Cardiovascular Chrononutrition

This randomized trial tested whether eating only during the daytime could protect heart health during simulated night shifts. Twenty healthy adults were assigned either to eat across both day and night (like typical shift workers) or to eat only during the day. After several days of simulated night work, those who ate both day and night showed signs of cardiovascular strain, including higher blood pressure, disrupted heart rhythm balance, and increased clotting risk. In contrast, those who ate only during the day did not show these negative changes, and their blood pressure actually went down slightly.

Determinants of Sleep Quality and Health Outcomes Among Night‑Shift Nurses: Cross‑sectional Study (China)

Circadian Cross-sectional Epidemiology

This cross-sectional study surveyed 711 night-shift nurses in China to identify factors linked with poor sleep quality and related outcomes. Over 90% of participants reported poor sleep, as measured by the Pittsburgh Sleep Quality Index. Key risk factors included higher education level, more years of night-shift work, poor quality of make-up sleep, irregular daily routines, and irregular diet. Poor sleep was strongly correlated with greater levels of chronic fatigue.

Effects of Taking a Nap or Break Immediately After a 16‑h Night Shift (Nurses)

Clinical Errors & incidents Extended shifts / Overtime

This quasi-experimental crossover study tested whether a short rest period immediately after a 16-hour night shift could improve recovery for nurses. Sixty-two nurses either took a 30-minute nap or break in a controlled nap environment or went straight home as usual. The nap/break significantly reduced fatigue right after the shift—especially symptoms like local pain and heaviness—though it did not lead to clear improvements in sleep quality later that day. The main benefit was immediate relief from work-related fatigue.

GLU24/7 study: cardiometabolic risk factors in night‑shift workers (protocol)

Cardiometabolic Cardiovascular CGM

The GLU24/7 study is a 2-year prospective cohort following 60 industrial workers in Norway—half on rotating night shifts and half day workers. Data collection is staged: an initial 6-week observational phase with payroll-verified schedules, continuous glucose monitoring, food diaries, and sleep tracking, followed by baseline cardiovascular exams, and finally a repeat assessment two years later. Researchers will measure blood sugar variability alongside inflammation, lipid profiles, arterial stiffness, intima–media thickness, blood pressure, and VO₂max to see whether repeated circadian disruption from night work accelerates metabolic and cardiovascular risk factors. The study is ongoing with no published results yet.

How Shift Work Affects Our Gut Microbiota

Chrononutrition Circadian Evidence review

This narrative review compiles research on how night-shift schedules may alter the gut microbiota and contribute to gastrointestinal problems. Studies suggest that disrupted sleep–wake cycles, irregular meal timing, and circadian misalignment can shift gut microbial communities, promoting inflammation and raising risks for conditions like ulcers, IBS, and reflux. However, the evidence remains inconsistent due to small sample sizes, varied study designs, and lack of standardized methods. The review concludes that while dysbiosis appears to be a plausible pathway linking shift work with gut and metabolic disease, larger, better-controlled studies are needed.

Intermittent Fasting for Weight Loss in Night‑Shift Workers: Three‑Arm Randomized Trial

Cardiometabolic Cardiovascular Chrononutrition

This three-arm randomized clinical trial in night-shift workers with overweight/obesity compared continuous energy restriction (CER) with two modified intermittent-fasting (IF) strategies: eating ~2100 kJ (~500 kcal) on two days per week scheduled either on days off/day shifts (IF:2D) or on night-shift days (IF:2N), for 24 weeks. All groups lost weight and improved metabolic markers, and there were no significant between-group differences for the co-primary outcomes (body weight and HOMA-IR). As secondary findings, IF:2D reduced total and LDL cholesterol vs CER. No serious adverse events were reported.

Low‑Level LED Light Therapy for Sleep and HRV in Shift‑Work Nurses: Randomized Trial

Anxiety Circadian Clinical trial

This randomized controlled trial tested low-level LED photobiomodulation (red/near-infrared, 660/850 nm) delivered by a wearable cap for 30 minutes, three times per week for four weeks in shift-working nurses with insomnia (n=64). Compared with no-treatment controls, the intervention group showed substantial improvements in insomnia severity and in depression, anxiety, and stress scores over the 4-week period. Heart-rate variability (HRV) measures did not differ significantly between groups. The trial was unblinded and lacked a sham control.

Meta‑analysis: Night‑Shift Work and Type 2 Diabetes Incidence

Age & aging BMI Cardiometabolic

This cohort-based meta-analysis (9 papers, 10 cohorts; >235k participants) found that night-shift workers had about a 30% higher incidence of type 2 diabetes than day workers (HR = 1.30, 95% CI 1.18–1.43). The association was clear in women (HR = 1.28) and not statistically significant in men (wide CI, smaller samples). Risk appeared greater with higher BMI (significant for BMI > 30 kg/m²; not significant for ≤30 kg/m²) and rose with longer exposure (>5–10 years of night shifts showed higher risk than shorter durations). Findings were similar across medical and non-medical jobs and across regions.

Night-Shift Work and Gastrointestinal Cancer Risk in Nurses: Review

Cancer Cardiometabolic Circadian

This narrative review looked at research on whether working night shifts increases the risk of gastrointestinal (GI) cancers, such as colorectal and stomach cancer, in nurses. The review highlights that long-term night-shift work can disrupt circadian rhythms, lower melatonin (a hormone that helps regulate sleep and has protective effects against cancer), and increase obesity and insulin resistance — all of which may raise cancer risk. Evidence is strongest for colorectal cancer, especially after 15 or more years of rotating night shifts, while results for stomach cancer are less consistent.

Optimizing the Potential Utility of Blue‑Blocking Glasses for Sleep and Circadian Health

Blue-blocking Blue-blocking glasses Circadian

This review examined the effectiveness of blue-blocking glasses as a tool for supporting circadian rhythms and sleep. The authors introduced a standardized metric (melanopic daylight filtering density, or mDFD) to rate how well different lenses reduce the type of light that delays melatonin release. Out of 26 commercially available products tested, only those with stronger filtering (mDFD ≥1) meaningfully reduced this light input. Evidence from intervention studies showed that when used correctly—such as after a night shift on the commute home or before trying to sleep during the day—blue-blocking glasses improved at least one circadian or sleep-related outcome. Effectiveness depended not only on filtering strength but also on timing and consistency of use.

Risk and Protective Factors for Shift‑Work Sleep Disorder (UK Biobank)

Age & aging BMI Circadian

This UK Biobank study analyzed data from more than 10,000 night-shift workers to identify factors linked to Shift-Work Sleep Disorder (SWSD), using insomnia symptoms as a proxy. About one in four workers met criteria for this proxy. Men had lower odds than women, and those identifying as Asian or Black also showed lower odds compared to White participants. Older age and higher BMI were associated with greater risk. Personality traits also mattered: higher sociability, warmth, and diligence appeared protective, while higher nervousness increased risk. In contrast, chronotype, smoking, alcohol use, and years in the current job showed no consistent associations.

Sleep Trajectories and All‑Cause Mortality Among Low‑Income Adults

Age & aging Cardiometabolic Cardiovascular

This prospective cohort study tracked nearly 47,000 low-income Black and White adults in the Southern U.S. over five years to see how sleep duration patterns related to long-term mortality. Researchers identified nine “sleep trajectories,” including stable healthy sleep (7–9 hours), consistently long or short sleep, and shifts between categories. About two-thirds of participants had suboptimal sleep patterns. Compared with those who maintained healthy sleep, participants in the long-long, short-long, and long-short groups had up to a 29% higher risk of all-cause death and similar increases for cardiovascular mortality. No significant links were found for cancer or neurodegenerative deaths. Associations were strongest among White adults with higher incomes, underscoring how both biological and social factors shape outcomes.

The effectiveness of time‑restricted eating as an intermittent fasting approach in shift workers (systematic review)

Cardiometabolic Chrononutrition Circadian

This systematic review and meta-analysis assessed six randomized trials testing time-restricted eating (TRE) among shift workers, focusing on glucose metabolism and sleep. Across studies, TRE produced small, non-significant changes in fasting glucose, insulin, insulin resistance, and post-meal glucose levels, with wide variability between trials. Sleep outcomes also showed no meaningful differences. Evidence quality was rated very low due to small sample sizes, inconsistent methods, and short study durations. The authors note that future research should test well-powered protocols using a 6–10 hour eating window—especially early-TRE paired with good sleep hygiene—and incorporate circadian biomarkers to clarify underlying mechanisms.

Melatonin for Daytime Sleep in Resident Trainees During Night Float

Circadian Clinical trial Fatigue & alertness

This randomized controlled trial is testing whether melatonin can improve daytime sleep in resident physicians working overnight shifts. Participants take a timed melatonin dose before attempting to sleep during the day, and researchers track outcomes such as sleep duration, sleep consolidation, and overall quality. The goal is to see if melatonin can help counteract the challenges of sleeping against the body’s natural rhythms. The trial is registered but has not yet published results.

Melatonin and Oxidative DNA Damage Repair in Night‑Shift Workers

Circadian Clinical trial Endocrine & hormones

This randomized controlled trial tested whether taking 3 mg of melatonin before daytime sleep could improve the body’s ability to repair cell damage in night-shift workers. Over four weeks, participants were assigned to either melatonin or placebo, and researchers measured markers of oxidative DNA damage repair. The results showed a borderline significant improvement in repair activity during daytime sleep among those who took melatonin, though no clear effects were seen during night work itself.

High‑Intensity Light Exposure for ICU Nurses on Night Shifts

Alertness Clinical trial Fatigue & alertness

This randomized controlled trial examined whether bright light could help ICU nurses stay more alert during night shifts. Nurses were exposed to high-intensity lighting (1,500–2,000 lux) early in the shift and compared with colleagues working under standard hospital lighting. The intervention reduced feelings of sleepiness but was also linked to more lapses on attention-based tasks. These results show both the potential and the limits of using strong light to manage fatigue in critical care environments.

Evening Blue‑Depleted Lighting in Hospital Wards

Blue-blocking Blue-blocking glasses Blue-depleted

This registered clinical trial will test whether adjusting hospital ward lighting in the evening to a warmer, blue-depleted spectrum can improve outcomes for night-shift staff. The study uses a ward-level crossover design, comparing standard hospital lighting with blue-depleted lighting during evening hours. Researchers will measure effects on melatonin suppression, post-shift sleep quality, and other circadian-related outcomes. Results have not yet been published.

Sleep Schedule Intervention for Shift‑Work Disorder

Actigraphy Circadian Clinical trial

This field trial is testing whether adjusting sleep schedules can improve symptoms of Shift-Work Disorder (SWD) in active night workers. Over three weeks, participants first follow their usual sleep routines, then transition to structured schedules that vary the timing of sleep—such as morning versus evening sleep periods. Researchers use actigraphy and symptom tracking to measure changes in sleep efficiency, alertness, and overall wellbeing. The trial is registered but has not yet published results.

Sleep & Circadian Treatments for Shift Workers (Field Trial)

Behavioral intervention Circadian Clinical trial

This field trial is testing a real-world program that combines several circadian and sleep strategies to help shift workers manage their schedules more effectively. The intervention includes structured sleep scheduling, timed light exposure, meal-timing guidance, and behavioral coaching delivered outside of a laboratory setting. Researchers will assess whether this package improves outcomes such as sleep quality, daytime alertness, and metabolic health markers. The study is registered but has not yet published results.

Skeletal Effects of Chronic Night Shift in New Nurse Hires

Bone health Circadian Clinical

This prospective cohort study is following newly hired nurses over their first year of working chronic night shifts to understand how night work affects bone health. Researchers are measuring markers of bone turnover, bone mineral density, and skeletal strength over time, then comparing results with nurses working daytime schedules. The goal is to see whether night-shift exposure early in a career has measurable effects on bone metabolism. The study is registered but has not yet published results.

Shift‑Work Biomarkers of Obesity Risk in Workers

Cardiometabolic Cardiovascular Circadian

This prospective cohort study is recruiting 1,000 participants from healthcare and industrial settings across five European countries—Austria, Denmark, Germany, the Netherlands, and Poland. It compares night-shift workers (rotating shifts with at least four nights per month over at least three years) against day workers, carefully matched by age, gender, and job roles. Researchers collect biological samples (blood, urine, saliva, hair, and feces) and behavioral data to assess markers related to metabolism, inflammation, appetite hormones, circadian disruption, oxidative stress, and the microbiome. As of August 27, 2025, no results have been published or posted.

Dietary Intervention to Mitigate Night‑Shift Effects

Chrononutrition Circadian Clinical trial

This registered dietary intervention protocol aims to determine whether a controlled meal schedule can reduce metabolic strain for healthy adults working night shifts. Participants complete two inpatient stays—receiving identical meals each time—while researchers collect detailed metabolic data including blood, urine, saliva, stool, and rectal swabs. The study, conducted by Brigham and Women’s Hospital and supported by the NHLBI, remains in the recruiting phase with no published results yet.

Mediterranean Diet Education in Shift‑Working Nurses

Cardiometabolic Cardiovascular Chrononutrition

This interventional study provides shift-working nurses with an educational program promoting Mediterranean-style eating. The program is designed to test whether improving adherence to this diet pattern can also enhance sleep quality and overall wellbeing in a shift-work population. The study remains in the registered phase with no published results yet.

Lemborexant in Shift‑Work Insomnia

Circadian Clinical trial Fatigue & alertness

This clinical trial is testing whether a sleep medication called lemborexant can help night-shift workers who have trouble sleeping during the day. Participants first go through a two-week observation period, then take either lemborexant or a placebo for two weeks. The main goal is to see if the medication helps them sleep longer and better after working night shifts. The study is still in the recruiting phase, and no results have been published yet.

Solriamfetol for Excessive Sleepiness in Shift Workers

Alertness Circadian Clinical trial

This clinical trial is studying whether solriamfetol, a wake-promoting medication, can help reduce excessive sleepiness in people working early-morning shifts. Participants take either solriamfetol or a placebo, and researchers measure changes in alertness, performance, and overall daily function. The study remains in the recruiting phase with no published results yet.

Circadian Phase Adjustment and Metabolic Control in Night‑Shift Workers

Cardiometabolic Cardiovascular Circadian

This multicenter, randomized, double-blind, placebo-controlled trial tested whether taking 2 mg melatonin for 12 weeks could help night-shift workers adjust their circadian phase and improve markers of metabolic and cardiovascular health. Participants were randomly assigned to melatonin or placebo, and researchers tracked outcomes such as circadian timing, glucose regulation, and other metabolic parameters. The study has been completed, but no results have been published yet.

The Healthy Heroes Study (Time‑Restricted Eating in Emergency Responders)

Cardiometabolic Cardiovascular Chrononutrition

This completed clinical trial tested whether 10-hour time‑restricted eating (TRE) is feasible and beneficial for emergency responders working 24-hour shifts. A total of 137 firefighters were randomly assigned to either TRE (eating within a 10-hour window) or standard eating habits. Over 12 weeks, TRE was not only well-tolerated but also led to several health improvements—especially among those at higher risk. Notably, TRE reduced the size of VLDL cholesterol particles and, for participants with elevated cardiometabolic risk, it lowered HbA1c levels (a marker of long-term blood sugar control) and diastolic blood pressure.

Acute Night Shift Work Elevates Ambulatory Blood Pressure

Blood pressure Cardiometabolic Cardiovascular

This quasi-randomized crossover study measured 24-hour blood pressure and sleep in 24 rotating shift workers across both day and night shifts in free-living conditions. Compared with day shifts, a single night shift led to higher systolic (107 vs 104 mmHg) and diastolic (67 vs 64 mmHg) blood pressure, blunted nighttime dipping (8% vs 12%), and much shorter sleep duration (≈4h vs 8h). These results show that even one night of shift work can acutely trigger cardiovascular risk markers in otherwise healthy young adults.

Optimization of Chrononutrition to Reduce the Risk of Disease in Shift Workers (SHIFT)

Alertness Chrononutrition Clinical trial

This randomized controlled trial, led by UC San Diego and the Salk Institute, is enrolling night-shift nurses to test whether meal timing can reduce health risks linked to shift work. Participants follow a 10-hour daytime eating window, with one group also receiving a low-glycemic snack during the night shift, while a comparison group continues with usual eating patterns. Researchers will track outcomes such as sleep, alertness, and metabolic health. The study is currently recruiting, with no published results yet.

Shift Worker Intervention for Sleep Health (SWISH – CBT‑I adapted for nights)

CBT-I Clinical trial Digital health

This randomized controlled trial is testing whether Cognitive Behavioral Therapy for Insomnia (CBT-I) can be adapted to the unique challenges of night-shift work. The program is delivered via telehealth and tailored for nurses who sleep during the day after overnight shifts, with adjustments to the timing of sleep strategies and behavior planning. Researchers will measure changes in sleep efficiency and insomnia severity to see if this adapted approach is as effective as traditional CBT-I. The trial is registered but has not yet published results.

Personalized Circadian mHealth App for Shift Workers (SHIFT app pilot)

Alertness App Circadian

This pilot trial is testing a mobile health app that uses data from wearable devices to give shift workers personalized guidance in real time. The app tracks patterns such as light exposure, sleep timing, and activity, then delivers tailored recommendations to better align daily routines with circadian rhythms. The study will evaluate whether this digital approach can improve sleep, alertness, and overall health in night-shift workers. The trial is registered but has not yet published results.

Night‑Shift Work and Female Breast Cancer: Two‑Stage Dose–Response Meta‑analysis

Cancer Meta‑analysis Night‑shift workers

Dose–response analysis indicates higher breast cancer risk with increasing duration/frequency of night‑shift exposure.

Bright Environmental Light and Sleepiness in Night‑Shift ICU Nurses

Laboratory simulation (human)

Fatigue & alertness Field study Light & environment

In ICU nurses, high‑intensity light during night shifts reduced sleepiness but increased some psychomotor errors, suggesting trade‑offs.

Fasting as an Intervention to Alter Impacts of Simulated Night‑Shift Work on Glucose Metabolism

Crossover randomized controlled trial

Chrononutrition Diabetes General population

Meal timing intervention (fasting across the night) mitigated impairments in glucose metabolism during simulated night shifts.