Study objectives: To analyze the independent and combined relations of sleep duration and midday napping with coronary heart diseases (CHD) incidence along with the underlying changes of cardiovascular disease (CVD) risk factors among Chinese adults.
Methods: We included 19,370 individuals aged 62.8 years at baseline from September 2008 to June 2010, and they were followed until October 2013. Cox proportional hazards models and general linear models were used for multivariate longitudinal analyses.
Results: Compared with sleeping 7- < 8 h/night, the hazard ratio (HR) of CHD incidence was 1.33 (95% CI = 1.10 to 1.62) for sleeping ≥ 10 h/night. The association was particularly evident among individuals who were normal weight and without diabetes. Similarly, the HR of incident CHD was 1.25 (95% CI = 1.05 to 1.49) for midday napping > 90 min compared with 1-30 min. When sleep duration and midday napping were combined, individuals having sleep duration ≥ 10 h and midday napping > 90 min were at a greater risk of CHD than those with sleeping 7- < 8 h and napping 1-30 min: the HR was 1.67 (95% CI = 1.04 to 2.66; P for trend = 0.017). In addition, longer sleep duration ≥ 10 h was significantly associated with increases in triglycerides and waist circumference, and a reduction in HDL-cholesterol; while longer midday napping > 90 min was related to increased waist circumference.
Conclusions: Both longer sleep duration and midday napping were independently and jointly associated with a higher risk of CHD incidence, and altered lipid profile and waist circumference may partially explain the relationships.
Keywords: follow-up; incident CHD; midday napping; prospective studies; sleep duration.
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