Context: Short sleep duration and poor sleep quality are associated with cardiovascular outcomes. One mechanism proposed to explain this association is altered diurnal cortisol secretion.
Objective: The objective of the study was to examine the associations of sleep duration and sleep quality with diurnal salivary cortisol levels.
Design: This was a cross-sectional analysis using data from examination 5 (2010-2012) of the Multi-Ethnic Study of Atherosclerosis. Actigraphy-based measures of sleep duration and efficiency were collected over 7 days, and salivary cortisol samples were collected over 2 days from participants aged 54-93 years (n = 600 with analyzable data).
Results: Shorter average sleep duration (<6 h/night) was associated with less pronounced late decline in cortisol [2.2% difference in slope; 95% confidence interval (CI) 0.8-3.7; P ≤ .01] and less pronounced wake-to-bed slope (2.2% difference; 95% CI 1.0-3.4; P ≤ .001) compared with longer sleep duration (≥6 h/night). Lower sleep efficiency (<85%) was associated with less pronounced early decline in cortisol (29.0% difference in slope; 95% CI 4.1-59.7; P < .05) compared with higher sleep efficiency (≥85%). Subjects reporting insomnia had a flatter cortisol awakening response (-16.1% difference in slope; 95% CI -34.6 to -0.1; P < .05) compared with those not reporting insomnia.
Conclusions: Shorter sleep duration, lower sleep efficiency, and insomnia are associated with alterations in diurnal cortisol levels consistent with changes in hypothalamic-pituitary-adrenal regulation.