Gender differences in nighttime sleep and daytime napping as predictors of mortality in older adults: The Rancho Bernardo Study

ObjectiveMany studies suggest optimal sleep duration for survival is 7–8 h/night. We report the gender-specific independent association of all-cause mortality with nighttime sleep and daytime nap duration in older adults who were followed for up to 19 years.MethodsBetween 1984 and 1987, 2001 community-dwelling, mostly retired, adults (1112 women), age 60–96 years, answered questions about health, mood, medications, life-style, daytime napping, and nighttime sleep duration. Vital status was confirmed for 96% through July 2001.ResultsAt baseline, men reported significantly longer nighttime sleep and daytime napping than women. In both men and women, nighttime sleep <6 h was associated with depressed mood and sleep-related medication, and ⩾9 h was associated with more alcohol consumption. Napping ⩾30 min was associated with prevalent depressed mood, coronary heart disease, and cancer. Of the group, 61% died over the next 19 years, at an average age of 85.6 years. Mortality risk was lowest among those sleeping 7–7.9 h/night in both men and women. Multiple-adjusted analyses showed that increased mortality was associated with nighttime sleep ⩾9 h in women (HR 1.51: 95% CI = 1.05–2.18), and with daytime napping ⩾30 min in men (HR 1.28: 95% CI, 1.00–1.64).ConclusionsMechanisms for these differences are unknown.