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=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=9 hours of sleep. A modestly stronger association with sleep duration or=9 hours/night) need further elucidation.