Sleep duration and risk of ischemic stroke in postmenopausal women.

BACKGROUND AND
PURPOSE: Many studies have shown a U-shape association between sleep duration and mortality, but epidemiological evidence linking cardiovascular diseases with habitual sleep patterns is limited and mixed.
METHODS: We conducted a prospective study on 93 175 older women (aged 50 to 79 years) in the Women's Health Initiative Observational study cohort to examine the risk of ischemic stroke in relation to self-reported sleep duration. Cox models were used to investigate the putative associations, adjusting for multiple sociodemographic and lifestyle factors, depression, snoring, sleepiness symptoms, and other cardiovascular disease-related clinical characteristics.
RESULTS: At baseline, 8.3% of subjects had reported their sleep duration as <or=5 hours per night and 4.6% reported long duration of sleep (>or=9 hours/night). After an average of 7.5 years of follow-up, 1166 cases of ischemic stroke had occurred. Multivariable-adjusted relative risk (RR) and 95% CI for ischemic stroke (using a sleep time of 7 hours/night as the reference) were 1.14 (0.97, 1.33), 1.24 (1.04, 1.47), and 1.70 (1.32, 2.21) for women reporting <or=6, 8, and >or=9 hours of sleep. A modestly stronger association with sleep duration <or=6 hours per night (RR, 1.22; 1.03, 1.44) was noted among women without prevalent cardiovascular disease at baseline. Our analyses also reveal that the adverse effect of long sleep is likely independent of the increased risk for ischemic stroke associated with frequent snoring and sleepiness (RR, 1.31; 1.00, 1.72).
CONCLUSIONS: Habitual sleep patterns are important neurobehavioral determinants of risk for ischemic stroke in postmenopausal women. The underlying neurobiology and mechanistic mediators for the putative adverse effect of long sleep (>or=9 hours/night) need further elucidation.