Are Short Duration Naps Better than Long Duration Naps for Mitigating Sleep Inertia? Brief Report of a Randomized Crossover Trial of Simulated Night Shift Work

OBJECTIVE: We sought to test the effects of different duration naps on post-nap cognitive performance during simulated night shifts. METHODS: We used a randomized laboratory-based crossover trial design with simulated 12-hr night shifts and each participant completing three conditions of 72 hrs each (Clinicaltrials.gov; registration # NCT04469803). The three conditions tested included no-nap, a 30-min nap opportunity, and a 2-hr nap opportunity. Naps occurred at 02:00 hrs. Cognitive performance was assessed with the Brief 3-min Psychomotor Vigilance Test (PVT-B). Four PVT-B measures include: reaction time (RT in milliseconds (ms)), lapses (RT > 355 ms), false starts (reactions before stimulus or RT <100 ms), and speed (1,000/RT). The PVT-B was performed at the start of the simulated night shift (19:00), end of shift (07:00), pre-nap (02:00), and at 0 mins, 10 mins, 20 mins, and 30 mins following the 30-min and 2-hr nap conditions. Simultaneously, participants reported subjective ratings of fatigue and other constructs. CONCLUSIONS: While sleep inertia was detectable immediately following short 30-min and long 2-hr nap opportunities during simulated night shift work, deficits in cognitive performance and subjective ratings quickly dissipated and were not detectable at 10-30 mins post-nap.