0172 PREVALENCE OF INSOMNIA AND EXCESSIVE DAYTIME SLEEPINESS IN US NAVY SAILORS

Abstract

The most common sleep-related complaint in civilian populations is insomnia. Workers in the U.S. Navy regularly experience significant levels of sleep deprivation and circadian misalignment due to long workdays and chronic shiftwork. This study assessed the prevalence of insomnia and elevated daytime sleepiness of crewmembers underway on a United States Navy ship while working. Crewmembers (N=166, n=90 working on a fixed watchstanding schedule, n=76 on a rotating schedule) from the Reactor Department of the USS NIMITZ volunteered in this study. Sleep was assessed with actigraphy. Insomnia was assessed with the Insomnia Severity Index (ISI), and the Epworth Sleepiness Scale (ESS) was used to assess sleepiness. Participants slept an average 6.75 ± 0.94 hours/day. ESS scores were negatively correlated with sleep duration (r=-0.175, p=0.033); ISI scores were positively correlated with the number of sleep episodes per day (r=0.221, p=0.007). ESS scores (mean=9.91 ± 4.66) indicated that 45% of the participants had excessive daytime sleepiness—EDS (ESS score>10). ISI scores (mean=11.5 ± 5.20) indicated that 66% of the participants have symptoms of insomnia (ISI score≥10). Approximately 36% of the participants had EDS and comorbid insomnia symptoms, 30% had insomnia without EDS, while 9% had EDS without insomnia symptoms. The prevalence of EDS and insomnia was modulated by the type of the watchstanding schedule. For participants on the fixed schedule, the prevalence of insomnia was 57% for the EDS group and 35% for the normal sleepiness group (p<0.001). In the rotating schedule, however, the prevalence of insomnia was ~86% for both EDS and normal sleepiness groups (p>0.9). Both excessive daytime sleepiness and insomnia remain problems for crewmembers working at sea. Results show that, as expected, sleepiness increased with level of sleep deprivation. The prevalence of insomnia increased dramatically when crewmembers worked rotating, non-circadian schedules in which their sleep was split into multiple episodes during the day. The latter result suggests that these rotating non-circadian schedules induce insomnia symptoms due to circadian misalignment and irregular sleep patterns.