Sleep duration and risk of coronary heart disease: A systematic review and meta-analysis of prospective cohort studies.

BACKGROUND: Epidemiological studies suggest an association between sleep duration and risk of coronary heart disease, however, the results are controversial. We conducted this systematic review and meta-analysis to summarize the potential dose-response relationship between sleep duration and risk of coronary heart disease.

METHODS: The electronic reference databases (PubMed and Embase) were searched through January 2016 with selection criteria for relevant studies. Both semiparametric and parametric methods were used to calculate the pooled risk estimates.

RESULTS: Seventeen articles with 22 independent reports involving 17,841 incident cases of coronary heart disease among 517,440 participants were included in our meta-analysis. A U-shaped relationship was detected between sleep duration and risk of coronary heart disease, with the lowest risk at 7-8h per day. Compared with 7h sleep duration per day, the combined relative risk of coronary heart disease were 1.11 (95% CI=1.05-1.16) for an reduction of 1h and 1.07 (95% CI=1.00-1.15) for an increment of 1h. And the results almost did not change in the subgroup analysis of gender and fatal cases. Exclusion of any single study did not alter the combined relative risk. In addition, visual inspection of funnel plots, Begg's and Egger's tests failed to identify publication bias.

CONCLUSIONS: Both short and long sleep durations are significantly associated with increased risk of coronary heart disease. Compared with 7h sleep duration per day, the risk of coronary heart disease increases 11% for an hour decrease and increases 7% for an hour increase.