Effects of operational naps on blood pressure and performance among night shift workers - ABSTRACT The overall aim of this Phase II trial is to determine the duration (dose) of overnight nap(s) that leads to restoration of normal blood pressure (BP) dipping and the least impairment of psychomotor performance post- nap (safety profile) among night shift workers, while accounting for caffeine use. Cardiovascular disease (CVD) exerts a disproportionate health burden on night shift workers, including public safety workers (PSWs) and healthcare workers (HCWs): our targeted population. Night shift work may increase CVD risk by repeated disruption of the naturally occurring decrease in BP known as BP dipping. Blunted BP dipping increases CVD risk and correlates with other preclinical indicators of CVD. We show that night shift workers are frequently exposed to blunted BP dipping, but short naps (<60 mins) can restore it. Restoring BP dipping, even briefly during night shift work, may improve cardiovascular health and mitigate CVD risk. Use and approval of naps is challenged by sleep inertia post-nap and its impact on performance and safety. In addition, caffeine is frequently used by night shift workers to address sleepiness, fatigue, and sleep inertia. We are left with an important question for safety-sensitive operations that must rely on night shift work yet want to address cardiovascular health of workers. What duration of a nap opportunity (dose) during night shift work supports cardiovascular health and psychomotor performance (a safety surrogate) while accounting for caffeine use? Our long-term goal is to reduce the risk of CVD and improve cardiovascular health of all night shift workers. We propose a Phase II randomized controlled trial (RCT) to test the efficacy of no-nap, 15, 30, 45, and 60-min nap opportunities on BP dipping and post-nap performance (safety) in 130 PSWs and HCWs. The co-primary outcomes will be the proportion of participants with a clinically meaningful dip in BP (>10%) during nap opportunities and severe impairment in psychomotor performance >10 mins post-nap. Our approach uses a Phase II trial, within-subject crossover design, with randomized order for 5 nap conditions (no-nap, 15, 30, 45, and 60-min) accounting for caffeine consumption. Each participant will complete only 4 nap conditions during simulated 12-hr night shifts. Milestones for Year 1 (R61) include finalizing the study protocol and recruitment strategies, obtaining regulatory approvals, completing staff training, and enrolling 5% of the target sample. Aim1 (R33): Test the effect of nap duration (dose) during night shift work on BP dipping. Hypothesis 1: Compared to shorter naps, longer naps will lead to a higher proportion of participants with a clinically meaningful >10% dip in BP. Aim2 (R33): Evaluate the safety profile of nap duration (dose) to inform employers and stakeholders of risk. Hypothesis 2: Odds of severe psychomotor impairment at >10 mins post-nap (measured with psychomotor vigilance test (PVT) lapses) increase with increased nap duration. Impact: Our study addresses NHLBI’s Objective #1, Understanding Normal Biological Function and Resilience, and Goal #4 of NIH’s Sleep Research Plan, testing “real world” interventions in shift workers.
