Effects of Operational Naps on Blood Pressure and Performance Among Night Shift Workers

Blunted blood pressure (BP) dipping is a well-described risk factor for cardiovascular disease (CVD) among older adults and individuals with chronic disease. Previous research shows that night shift workers are at risk and repeatedly exposed to blunted BP dipping as a consequence of sleep loss and irregular sleep. While occasional episodes of blunted BP dipping may not be harmful, repetitive exposure over years of night shift work, as experienced by public safety workers (PSWs) and healthcare workers (HCWs), is likely detrimental to cardiovascular health and increases risk of CVD. Recent research shows that exposure can be mitigated with brief on-duty naps, which briefly restore normal BP dipping. Despite these data, there is legitimate clinical equipoise regarding the optimal on-duty nap duration (dose) needed to maximize BP dipping and minimize threats to post-nap psychomotor performance (i.e., sleep inertia).

This study will use a Phase II, within subject, crossover, incomplete block randomized trial design to test the efficacy of 5 overnight on-duty nap conditions: no-nap, 15, 30, 45, and 60-minutes. The primary outcome is the proportion of participants with a clinically meaningful greater than or equal to 10% dip in BP during nap opportunities. The secondary outcome is focused on deficits in psychomotor performance at greater than or equal to 10 mins post-nap: a safety-critical moment for PSWs and HCWs.

Goal enrollment is set at 130, accounting for attrition. Each condition begins with 36 hours of at-home monitoring with non-invasive devices. The last 12 hours of each condition includes a 12-hour simulated night shift with nap opportunities provided at 0200 hours with the nap duration determined by the randomization schema. During the simulated night shift, participants will be continuously monitored with non-invasive devices, allowed to consume controlled amounts of caffeine, and complete standardized tests of psychomotor performance. Participants will be blinded to nap duration and caffeine dose. Volunteer participants will be asked to complete 4 of the 5 nap conditions.

Inclusion criteria

• non-pregnant adults (>18 years of age)
• certified public safety/healthcare shift worker
• is an active shift worker
• resides within the Western Pennsylvania region within reasonable driving distance

Exclusion criteria

• current use of medication for cardiovascular disease (e.g., hypertension)
• prior or current diagnosis of sleep apnea, narcolepsy, restless leg syndrome, ischemic heart disease, heart failure, stroke, chronic kidney disease, chronic liver disease, rheumatologic disease requiring prescription medication, and cancer requiring treatment in past 2 years
• undiagnosed severe sleep apnea (Apnea-Hypopnea Index >30) based on at-home test
• Abstains from caffeine or reports adverse effects from caffeine use