Self-Reported Sleep Duration and Sleep Disturbance Are Independently Associated with Cortisol Secretion in the Whitehall II Study

Abstract

CONTEXT: The association of short sleep duration with cortisol secretion has not been thoroughly examined in large community dwelling populations and the relative importance of short sleep duration and sleep disturbance is unclear. OBJECTIVE: The objective of the study was to assess the relationships between self-reported sleep duration, sleep disturbance, and salivary cortisol secretion. DESIGN: This was a cross-sectional analysis using data from phase 7 (2002-2004) of the Whitehall II study. Sleep disturbances were assessed using a modified version of the Jenkins Scale. SETTING: The occupational cohort was originally recruited in 1985-1989. PARTICIPANTS: Analyses included 2751 participants with complete cortisol measures and who collected their first sample within 15 min of waking, were not on medication affecting cortisol secretion, and had complete information for all covariates. OUTCOME MEASURE: Six saliva samples were taken on waking, waking + 0.5, 2.5, 8, and 12 h and bedtime for the assessment of the cortisol awakening response and the slope in cortisol secretion across the day. RESULTS: In mutually adjusted analyses, both sleep duration and disturbances were independently associated with a flatter diurnal slope in cortisol secretion, such that evening cortisol secretion was raised in those reporting short sleep duration and high sleep disturbance. Short sleep duration was also associated with the cortisol awakening response. These effects were independent of a number of covariates, including waking time on day of sampling and stress on the day of cortisol assessment. CONCLUSION: Short sleep duration and increased sleep disturbances are independently associated with diurnal slope in cortisol secretion of a large community-based cohort of middle-aged men and women.