Impact of Sleep Habits on 5-Year Survival in Elderly Individuals and Long-Livers

Abstract

Background. Healthy, good quality sleep is one of the necessary conditions for achieving longevity and improving survival. Numerous general population studies have revealed a relationship between some sleep-related habits and mortality, but the results of similar studies conducted in older age groups are not so unambiguous. Aim. To study the impact of sleep-related habits on 5-year survival in subjects aged ≥75 years. Materials and methods. The study included 223 subjects (24% men) aged 75–98 years (median 87 years) who lived in Moscow and Moscow region and were undergoing preplanned inpatient treatment at the Russian Gerontology Research and Clinical Center in 2011–2013. Upon admission to hospital, the patients were surveyed using a specially developed questionnaire in order to assess social and behavioral factors such as lifestyle, habits, diet, and physical activity. The sleep-related questionnaire included the following: (i) bedtime; (ii) wake-up time; (iii) nighttime sleep duration; (iv) daytime napping. After discharge, the patients were under follow-up for 5 years. Deaths from all causes were recorded. Results. During the 5 years of follow-up (median 3.63 years), 88 (39.5%) people died. Accordingly, the 5-year survival rate was 60.5%, and the mean survival time was 4.44 [95% confidence interval (CI): 4.19–4.71] years. The study demonstrates that most of the subjects went to bed at 22:00–00:00 (65%), woke up 6:00–8:00 (58%), had a daytime nap (61%), and 68% of the participants had a nighttime sleep duration of between 7 and 9 h. Univariate regression analysis shows that a late (after midnight) bedtime, waking up after 8:00, and a long (≥10 h) nighttime sleep are associated with a 1.7–2.1-fold increased risk of death over 5 years. On the contrary, an early (before midnight) bedtime, waking up between 4:00 and 8:00, and nighttime sleep of 5–9 h, are associated with a 43–52% decreased risk of death over this period. Daytime napping had no effect on 5-year survival. Multivariate regression analysis demonstrates that age (hazard ratio [HR] 1.09; 95% CI: 1.02–1.17; p = 0.019), early (before midnight) bedtimes (HR 0.55; 95% CI: 0.31–0.97; p = 0.040), and 5–9 h nighttime sleep duration (HR 0.44; 95% CI: 0.26–0.76; p = 0.003) are independent predictors of 5-year survival. Conclusions. In subjects aged ≥75 years who lived in Moscow and Moscow region, early (before midnight) bedtime and moderate (5–9 h) nighttime sleep duration are independent predictors of 5-year survival and are associated with a 45 and 56% reduction in the risk of mortality, respectively, which indicates that sleep may be a geroprotective factor.