Relationship of Sleep Duration With All‐Cause Mortality and Cardiovascular Events: A Systematic Review and Dose‐Response Meta‐Analysis of Prospective Cohort Studies

BACKGROUND Effects of extreme sleep duration on risk of mortality and cardiovascular outcomes remain controversial. We aimed to quantify the dose-response relationships of sleep duration with risk of all-cause mortality, total cardiovascular disease, coronary heart disease, and stroke. METHODS AND RESULTS PubMed and Embase were systematically searched for prospective cohort studies published before December 1, 2016, that examined the associations between sleep duration and at least 1 of the 4 outcomes in generally healthy populations. U-shaped associations were indicated between sleep duration and risk of all outcomes, with the lowest risk observed for ≈7-hour sleep duration per day, which was varied little by sex. For all-cause mortality, when sleep duration was <7 hours per day, the pooled relative risk (RR) was 1.06 (95% CI, 1.04-1.07) per 1-hour reduction; when sleep duration was >7 hours per day, the pooled RR was 1.13 (95% CI, 1.11-1.15) per 1-hour increment. For total cardiovascular disease, the pooled RR was 1.06 (95% CI, 1.03-1.08) per 1-hour reduction and 1.12 (95% CI, 1.08-1.16) per 1-hour increment of sleep duration. For coronary heart disease, the pooled RR was 1.07 (95% CI, 1.03-1.12) per 1-hour reduction and 1.05 (95% CI, 1.00-1.10) per 1-hour increment of sleep duration. For stroke, the pooled RR was 1.05 (95% CI, 1.01-1.09) per 1-hour reduction and 1.18 (95% CI, 1.14-1.21) per 1-hour increment of sleep duration. CONCLUSIONS Our findings indicate that both short and long sleep duration is associated with an increased risk of all-cause mortality and cardiovascular events.