Impact of sleep-related habits on the 5-year survival rate in elderly and long-living individuals

BACKGROUND . Healthy, good quality sleep is one of the necessary conditions for achieving longevity and enhancing survival. Numerous general population studies revealed a relationship between some sleep-related habits and mortality, but the results of similar studies conducted in older participants are not so unambiguous. AIM . To study the impact of sleep-related habits on the 5-year survival rate in participants aged ≥75 years. MATERIALS AND METHODS . The study included 223 participants (24% men) aged 75–98 years (median age: 87 years) who lived in Moscow and the Moscow region and were receiving routine inpatient care at the Russian Gerontology Clinical Research Center in 2011–2013. At admission, 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 questionnaire included the following sleep-related items: 1) bedtime; 2) wake-up time; 3) nighttime sleep duration; 4) daytime napping. After discharge, patients were under follow-up for 5 years. Cases of all-cause mortality were registered. RESULTS . During 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 demonstrated that the most of the participants went to bed at 10–12 p.m. (65%), woke up at 6–8 a.m. (58%) and had a daytime napping (61%), and 68% of the participants had the duration of nighttime sleep within 7–9 h. Univariate regression analysis showed that late (after midnight) bedtime, waking up after 8 a.m., and long (≥10 h) nighttime sleep were associated with a 1.7–2.1-fold increase in the risk of death over the next 5 years. On the contrary, early (before midnight) bedtime, waking up between 4–8 a.m., and nighttime sleep for 5–9 h were associated with a 43–52% decrease in the risk of death over this period. Daytime napping had no effect on the 5-year survival rate. Multivariate regression analysis demonstrated that age (hazard ratio [HR] 1.09; 95% CI 1.02–1.17; p = 0.019), early (before midnight) bedtime (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) were independent predictors of the 5-year survival rate. CONCLUSION . In participants aged ≥75 years, who lived in Moscow and the Moscow region, early (before midnight) bedtime and medium (5–9 h) nighttime sleep duration are independent predictors for the 5-year survival rate and are associated with 45% and 56% reduction in the mortality risk, respectively, suggesting that a proper sleep may be a geroprotective factor.