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

Abstract

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.

Results

Twenty-eight (15 female), mostly certified emergency medical technicians or paramedics, consented to participate. For all three conditions, looking within condition, PVT-B lapse performance at the end of the 12-hr simulated night shift (at 07:00) was poorer compared to shift start (p < 0.05). Performance on PVT-B speed, RT, and false starts were poorer at shift end than shift start for the no-nap and 30-min nap conditions (p < 0.05), but not for the 2-hr nap condition (p > 0.05). Compared to pre-nap measures, performance on the PVT-B assessed at 0 mins post-nap showed significant performance declines for lapses and speed for both the 30-min and 2-hr nap conditions (p < 0.05), but not at 10, 20, or 30 mins post-nap. After waking from the 2-hr on-shift nap opportunity (at 0 mins), participants rated sleepiness, difficulty with concentration, and alertness poorer than pre-nap (p < 0.05). Participants in the 30-min nap condition rated alertness poorer immediately after the nap (at 0 mins) compared to pre-nap (p < 0.05)

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.

View correction statement:

Correction

This article is related to:

Comment on “The Emergency Medical Services Sleep Health Study” from the US Department of Transportation

Effect of Short versus Long Duration Naps on Blood Pressure during Simulated Night Shift Work: A Randomized Crossover Trial

Effect of Short versus Long Duration Naps on Blood Pressure during Simulated Night Shift Work: A Randomized Crossover Trial

Author Contribution

Authors PDP, TSO, DGLR, MDW, CGP, and LSW contributed to study conception and study design. Authors PDP, TSO, DGLR, MDW, CGP, MAS, JSDS, HB, GG, AA, CMW, DJ, SEM, and LSW contributed to execution of the study protocol and data collection. Authors PDP, TSO, DGLR, CJH, MDW, CGP, MAS, JSDS, HB, GG, AA, CMW, DJ, SEM, and LSW contributed the analysis of study data and interpretation of study findings. All authors contributed to reporting of study results and writing the manuscript.

Data Availability Statement

Access to study data by outside investigators will be reviewed on a case-by-case basis and sharing of these data will follow guidance from the University of Pittsburgh.

Clinical Trials Registration

ClinicalTrials.gov, NCT04469803. Registered on 9 July 2020.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Authors PDP and LSW report funding for this study from the ZOLL Foundation. Authors PDP, CGP, MDW, and LSW report funding for research from the Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. Author CJH reports funding from the National Aeronautics and Space Administration. Authors CGP, MDW, and LSW report funding for research from the National Institutes of Health.