Two‑nap strategy in simulated night work: a 90‑min followed by a 30‑min nap maintains performance
Summary
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.
Why It Matters For Night Shift Workers and Night Owls
In night work, alertness typically dips when safety-critical tasks cluster—after midnight and toward dawn. This study suggests that structuring rest as two planned naps, rather than relying on a single block of sleep or staying awake, can differentially support key outcomes (fatigue reduction vs. early-morning performance), with the trade-off that longer naps may briefly impair alertness on awakening. For organizations and workers evaluating fatigue-risk management options, these results offer a rationale for testing split-nap schedules under real-world constraints, while recognizing that effects may vary by workforce, workload, and setting and that larger field trials are needed to confirm benefits and refine timing.
Notes
Sleep Medicine, 2024.