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

Abstract

Objective

Blunting of the sleep-related dip in blood pressure (BP) has been linked to numerous cardiovascular outcomes including myocardial infarction. Blunting of BP dipping occurs during night shift work and previous research suggest that a 60-min or longer on-shift nap is needed to restore normal/healthy BP dipping. We sought to determine the effect of different durations of napping on BP during and following simulated night shifts. We hypothesized that the greatest benefit in terms of restoration of normal BP dipping during night shift work would be observed during a longer duration nap versus a shorter nap opportunity.

Methods

We used a randomized crossover laboratory-based study design. Participants consented to complete three separate 72-hr conditions that included a 12-hr simulated night shift. Nap conditions included a 30-min and 2-hr nap compared to a no-nap condition. Ambulatory BP monitoring was assessed hourly and every 10-30 mins during in-lab naps. Blunted BP dipping during in-lab naps was the primary outcome. Goal enrollment of 25 (35 with attrition) provided 80% power to detect a mean difference of 5 mmHg in BP between nap conditions.

Results

Of the 58 screened, 28 were consented, and 26 completed all three 72-hr conditions. More than half (53.6%) were female. Mean age was 24.4 years (SD7.2). Most (85.7%) were certified as emergency medical technicians or paramedics. The mean percentage dip in systolic BP (SBP) and diastolic BP (DBP) did not differ between the 30-min and 2-hr nap conditions (p > 0.05), yet a greater proportion of participants experienced a 10-20% dip in SBP or DBP during the 2-hr nap versus the 30-min nap (p < 0.05). For every additional minute of total sleep during the 30-min nap, the percentage of SBP dip improved by 0.60%, and the percentage of DBP dip improved by 0.68% (p < 0.05). These improvements approximate to a 6% per minute relative advancement toward normal/healthy BP dipping.

Conclusions

Restoration of a normal/healthy dip in BP is achievable during short and long duration nap opportunities during simulated night shift work. Our findings support the hypothesis that BP dipping is more common during longer 2-hr versus shorter 30-min naps.

Trial registration

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

View correction statement:

Correction

This article is related to:

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

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

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

Author Contribution

Authors PDP, TSO, DGLR, MDW, CGP, and LSW contributed to study conception and study design. All authors participated in execution of the study protocol and data collection activities. Authors PDP, TSO, DGLR, MDW, CGP, SEM, JRH, CE, AR, QM, and LSW participated in data analyses. All authors participated in synthesis and interpretation of study findings and writing of the manuscript.

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 (no grant number provided). 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. Authors CGP, MDW, and LSW report funding for research from the National Institutes of Health.