Sleep duration and risk of myocardial infarction and all-cause death in a Chinese population: the Kailuan study

Objective: Although sleep is one of the most important health-related factors, the association of sleep duration with incidence of myocardial infarction or all-cause death has not been fully understood, especially in the general Chinese population. The objective of this study was to explore the relationship between sleep duration and risk of myocardial infarction and all-cause death in China. Methods: Out of the 101,510 participants who were originally included into the Kailuan prospective cohort study and followed up for an average of 3.98 years, 95,903 participants were actually sampled to evaluate the impacts of sleep duration on myocardial infarction and all-cause death. Sleep duration was categorized as <= 5, 6, 7, and 8 hours/night, and >= 9 hours per night. Cox proportional hazards models were used to analyze the association of sleep duration with the incidence of myocardial infarction and all-cause death. Results: After a mean follow-up period of 3.98 years, 423 participants developed myocardial infarction and 1793 participants died. A U-shape association between sleep duration and all-cause death was found. The age-and gender-adjusted hazard ratios (95% confidence interval [CI]) of all-cause death (with seven hours of daily sleep being considered for the reference group) for individuals reporting <= 5, 6, and 8 hours, and >= 9 hours were 1.29 (1.08-1.55), 0.97 (0.82-1.14), 1.11 (0.97-1.27), and 1.77 (1.31-2.38), respectively, with a p <= 0.01. However, no significant associationwas seen between sleep duration and myocardial infarction. Conclusion: Both short and long duration of sleep might be potential predictors/markers for all-cause death, but not for myocardial infarction. (C) 2015 Elsevier B.V. All rights reserved.