Chronotype and self-reported sleep, alertness, and mental health in U.S. sailors.

Service members are at risk for sleep and psychological conditions affecting their readiness. Chronotype ("morningness" or "eveningness") is strongly associated with sleep, health and performance. The objective of this study was to examine associations between validated measures of chronotype and sleep quality, daytime functioning, alertness, and symptoms of depression, anxiety, and post-traumatic stress disorder (PTSD) in US service members (n = 298). Although predominantly young males (who skew toward eveningness in civilian populations), these Sailors skewed toward morningness (35.6% morning, 51.3% intermediate). Eveningness was associated with symptoms of depression and post-traumatic stress disorder (PTSD) (P < 0.01), less time in bed (P < 0.05), more sleep disruption (P < 0.01), and poorer daytime functioning and alertness (P < 0.05). Evening types were less likely to consider sleep important for performance (P < 0.05). To maximize service member readiness, schedules should be aligned with endogenous rhythms, whenever possible, and evening chronotypes may benefit from targeted interventions. Chronotype should be examined alongside health and readiness in service members.