0167 Influence of light exposure, exercise, caffeine intake, and nicotine use on sleep of U.S. Navy sailors during home port operations

Abstract Introduction Insufficient sleep is pervasive in U.S. Navy (USN) sailors and has been associated with increased risk of injury and mood disturbances. As such, monitoring sleep and identifying modifiable targets that influence sleep in this population is essential. We examined the sleep of USN sailors during 9-months in port and explored the influence of different lifestyle behaviors on sleep. Methods Sailors (n = 101, 31 ± 7 years old [mean ± SD], 21% female) wore a commercial wearable sleep-tracking device (Oura Ring, Gen2) during a 9-month home port maintenance period (September 2021 – May 2022). During the study, the sailors slept at home and had periods working on the ship (on-hull; higher demands) and off the ship (off-hull; lower demands). Participants also completed 5 self-report surveys that assessed sleep quality (Pittsburgh Sleep Quality Index; PSQI) and multiple lifestyle behaviors including: hours of natural light exposure, hours of moderate/vigorous physical activity, and intake of caffeine, nicotine, and alcohol. Sleep outcome measures from the wearable device included total sleep time (TST), standard deviation of TST (SD TST), and sleep efficiency (SE). Linear mixed models were used to examine the effects of lifestyle behaviors on sleep. Timepoint and on/off-hull condition were also included as fixed effects, while participant was included as a random effect. Results Participants slept 6.5 ± 0.7 hours a night (6.2 ± 0.9 on-hull; 6.4 ± 0.8 off-hull; p > .05) and had slightly elevated PSQI scores that were higher on-hull (8.3 ± 4.6) than off-hull (6.5 ± 3.5; B = 1.83, Std. Error = 0.71, p = .01). Lifestyle behaviors were not significant predictors of PSQI, TST, SD TST, or SE (p > .05). Conclusion Lifestyle behaviors had weak relationships with self-reported and objective sleep outcomes in this exploratory analysis. Therefore, modifying lifestyle behaviors may not significantly influence sleep in USN sailors during home port periods. Still, additional behavioral targets (e.g., diet), specific aspects of behavioral outcomes (e.g., light exposure timing, exercise intensity), and other work-related factors (e.g., workload, schedule) that can affect sleep should be explored in future efforts. Support (if any) Military Operational Medicine Research Program (work unit no. N2010).