Insomnia and Sleep Duration as Mediators of the Relationship Between Depression and Hypertension Incidence

BACKGROUND Depression has been found to predict the incidence of hypertension and other adverse cardiovascular events in prospective studies. Insomnia and short sleep duration, which are typical symptoms of depression, have also been shown to increase the risk for hypertension incidence. Insomnia is associated with increased activation of the hypothalamic-pituitary-adrenal axis, and short sleep duration raises average 24-h blood pressure, which over time could lead to structural adaptations that gradually reset the entire cardiovascular system to operate at an elevated pressure equilibrium. No previous published population studies have examined whether insomnia and sleep duration mediate the relationship between depression and hypertension incidence. METHODS We conducted multivariate longitudinal (1982-1992) analyses stratified by age of the First National Health and Nutrition Examination Survey (NHANES 1) (n = 4,913) using Cox proportional hazards models. RESULTS Middle-aged subjects who suffered from depression at baseline were 44% more likely to be diagnosed with hypertension over the follow-up period after controlling for covariates (hazard ratio (HR) = 1.44, 95% confidence interval (CI) 1.15-1.80). Both short sleep duration and insomnia were also significantly associated with hypertension incidence. Consistent with insomnia and sleep duration acting as mediators of the relationship between depression and hypertension incidence, the inclusion of these variables in the multivariate models appreciably attenuated the association (HR = 1.27, 95% CI 1.00-1.61). Depression, sleep duration, and insomnia were not significantly associated with hypertension incidence in elderly subjects. CONCLUSIONS These results suggest the hypothesis that treatment of sleep problems in middle-aged individuals suffering from depression could reduce their risk for developing hypertension, and its vascular and cardiac complications.