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Sleep Quality, Occupational Factors, and Psychomotor Vigilance Performance in U.S. Navy Sailors.

STUDY OBJECTIVES
This field study a) assessed sleep quality of sailors on United States Navy (USN) ships while underway, b) investigated whether the Pittsburgh Sleep Quality Index (PSQI) scores were affected by occupational factors and sleep attributes, and c) assessed whether the PSQI could predict impaired psychomotor vigilance performance.


METHODS
Longitudinal field assessment of fit-for-duty USN sailors performing their underway duties (N=944, 79.0% males, median age 26 years). Participants completed questionnaires, wore actigraphs, completed logs, and performed the wrist-worn 3-minute Psychomotor Vigilance Task (PVT).


RESULTS
Sailors slept on average 6.60±1.01 hours/day with 86.9% splitting their sleep into more than one episode/day. The median PSQI Global score was 8 (IQR=5); 80.4% of the population were classified as "poor sleepers" with PSQI scores>5. PSQI scores were affected by sailor occupational group, rank, daily sleep duration, and number of sleep episodes/day. Sleep quality showed a U-shape association with daily sleep duration due to the confounding effect of split sleep. Sailors with PSQI scores>9 had 21.1% slower reaction times (p<0.001) and 32.8% to 61.5% more lapses combined with false starts (all p<0.001) than sailors with PSQI scores>9. Compared to males and officers, females and enlisted personnel had 86% and 23% higher risk, respectively, of having PSQI scores>9. Sailors in the PSQI>9 group had more pronounced split sleep.


CONCLUSIONS
Working on Navy ships is associated with elevated PSQI scores, a high incidence of poor sleep, and degraded psychomotor vigilance performance. The widely used PSQI score>5 criterion should be further validated in active-duty service member populations.