Self-reported sleep and nap habits and risk of mortality in a large cohort of older women

OBJECTIVES: To determine the association between self-reported sleep and nap habits and mortality in a large cohort of older women. DESIGN: Study of Osteoporotic Fractures prospective cohort study. SETTING: Four communities within the United States. PARTICIPANTS: Eight thousand one hundred one Caucasian women aged 69 and older (mean age 77.0). MEASUREMENTS: Sleep and nap habits were assessed using a questionnaire at the fourth clinic visit (1993/94). Deaths during 7 years of follow-up were confirmed with death certificates. Underlying cause of death was assigned according to the International Classification of Diseases, Ninth Revision, Clinical Modification. RESULTS: In multivariate models, women who reported napping daily were 44% more likely to die from any cause (95% confidence interval (CI)=1.23-1.67), 58% more likely to die from cardiovascular causes (95% CI=1.25-2.00), and 59% more likely to die from noncardiovascular noncancer causes (95% CI=1.24-2.03) than women who did not nap daily. This relationship remained significant in relatively healthy women (those who reported no comorbidities). Women who slept 9 to 10 hours per 24 hours were at greater risk of death from cardiovascular and other (noncardiovascular, noncancer) causes than those who reported sleeping 8 to 9 hours. CONCLUSION: Older women who reported napping daily or sleeping at least 9 hours per 24 hours are at greater risk of death from all causes except cancer. Future research could determine whether specific sleep disorders contribute to these relationships.