0216 The relationship between work and sleep in the naval operational environment

Abstract

Abstract Introduction Several studies conducted by the Naval Postgraduate School Crew Endurance Team have shown that a sailor’s life at sea is characterized by limited opportunities to sleep and long work hours. In this environment, which is saturated with work duties, time is a rare commodity. This study assesses how work hours affect sleep duration. The information presented herein is a subset of the measures taken from multiple field assessments on sailors aboard nine different USN ships. Methods Longitudinal (average = 11 days; range = 7 to 18 days), prospective, naturalistic observations were made of sailors (N=675; 18-59 years of age, 79.3% males, 85.3% enlisted) while performing their normal underway duties on nine US Navy surface ships. Activity logs were used to assess work hours, messing (meals), and personal time. Sleep was objectively assessed by actigraphs. Results The average sailor’s workday was 11.6 hours (s.d.=2.48). Sailors slept on average 6.53 hours/day (s.d.=0.97), a median 1.34 hours/day (IQR=0.88) were spent messing/eating and a median 3.25 hours/day (IQR=2.50) were reported for personal time. Work hours were associated with daily sleep duration (F(1,602)=105, p < 0.001; R2=0.148), personal time (F(1,673)=1539, p < 0.001; R2=0.696), and messing time (F(1,673)=32.0, p< 0.001; R2=0.044). Within the range of our data, every extra hour of work was associated with an average of ~9 minutes less sleep, ~41 minutes less personal time, and ~3 minutes less time at meals. The association between work hours and sleep duration was evident (all p< 0.001) even after adjusting for confounding factors, i.e., watchstanding status (watchstander, non-watchstander), type of watch schedule (fixed, rotating), rank group (officer, enlisted), and detailed rank group (E1-E3, E4-E6, E7-E9, O1-O3, O4-O6). Conclusion The naval operational environment is dominated by long work hours that, in turn, lead to sleep deprivation. The competing relation between work and sleep, however, is ameliorated by the existence of personal time (i.e., spare time in which sailors do not work). More research should be focused on spare time and its importance for sailor wellbeing while underway. Support (if any)