Morning Cortisol Is Associated With Stress and Sleep in Elite Military Men: A Brief Report.

Introduction: Accumulating evidence suggests that trends in salivary cortisol after awakening may be reliable biological predictors of morbidity and mortality. In a sample of elite military men, our lab recently established summary parameters of morning cortisol as well as their stability across 2 d of repeated sampling.

Materials and Methods: In this follow-on study, we evaluated summary parameters and their relationships to theoretically relevant demographic (i.e., age, body mass index) and biobehavioral correlates (i.e., blood pressure [BP], sleep parameters, fatigue, and perceived stress). Fifty-eight male active duty U.S. Navy SEALs self-collected salivary samples on 2 consecutive, midweek workdays upon waking (WAKE), WAKE+30 min, WAKE+60 min, 4 p.m., and 9 p.m. in a nondeployed, free-living setting. Resting BP was measured manually, and sleep-wake periods were objectively derived using actigraphy. Daily fatigue and perceived stress were measured by self-report. Summary parameters of morning cortisol magnitude (i.e., peak value [Peak], area under the curve in terms of ground [AUCG], and average of morning samples [AVE]) were assessed with respect to each demographic and biobehavioral item via correlational analyses. A subgroup of 29 participants was selected for compliance with salivary sampling in the morning across 2 d.

Results: Perceived stress was positively associated with Peak (r[27] = 0.437, p < 0.05), AUCG (r[25] = 0.500, p < 0.01), and AVE (r[25] = 0.506, p < 0.01). Total sleep time was also positively associated with Peak (r[26] = 0.378, p < 0.05). There were borderline associations between some summary parameters and diastolic BP, percent sleep, and wake after sleep onset. Age, systolic BP, body mass index, time in bed, sleep efficiency, and fatigue did not associate with morning cortisol.

Conclusions: Preliminary evidence of morning cortisol summary parameters as biobehavioral indicators was established, and these parameters appeared to associate with stress and sleep in elite military men.