Daytime sleepiness and risk of coronary heart disease and stroke: results from the Nurses' Health Study II.

OBJECTIVE: The objective of this study was to determine whether daytime sleepiness is independently associated with coronary heart disease (CHD) and stroke or whether the positive association is explained by short sleep duration, disturbed sleep, and circadian disruption, conditions that are associated with cardiometabolic risk factors for vascular events.

METHODS: Longitudinal analyses of data from the Nurses' Health Study II comprising 84,003 female registered nurses aged 37-54 at baseline were conducted in 2001 with follow-up until 2009. Multivariate Cox regression was used to explore the relationship between reported daytime sleepiness and the incidence of either CHD or stroke (n=500 cases).

RESULTS: Women who reported daytime sleepiness almost every day, compared with rarely/never, had an elevated adjusted risk of cardiovascular disease (CVD) (hazard ratio (HR)=1.58, 95% confidence interval (CI) 1.15-2.17). Controlling for sleep variables (sleep duration, snoring, shift work, and sleep adequacy) or potential metabolic biological mediators of disrupted sleep (diabetes, hypercholesterolemia, and hypertension) appreciably attenuated the relationship (HR=1.17, 95% CI 0.84-1.65; and HR=1.34, 95% CI 0.97-1.85, respectively). Controlling for both sleep variables and metabolic risk factors eliminated an independent association (HR=1.09, 95% CI 0.77-1.53). A similar pattern was observed for CHD and stroke individually.

CONCLUSIONS: Daytime sleepiness was not an independent risk factor for CVD in this cohort of women, but rather, was associated with sleep characteristics and metabolic abnormalities that are risk factors for CVD.