Bright Light Treatment During Three Consecutive Night Shifts: Mixed Results in Nurses
Summary
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.
Why It Matters For Night Shift Workers and Night Owls
This study shows that while bright light is often promoted as a tool to fight fatigue, its benefits can be limited in real hospital schedules. For night workers, it means light exposure might help a little with feelings of drowsiness, but it’s unlikely to keep performance steady on its own. The most practical takeaway is that bright light may work better when combined with other strategies—like strategic naps, adjusting shift timing, and ensuring a dark, quiet sleep environment during the day.
Notes
Useful null results when planning lighting changes.