Sleep duration and risk of stroke and coronary heart disease: a 9-year community-based prospective study of 0.5 million Chinese adults

Abstract Background There is uncertainty about the optimum sleep duration for risk of different subtypes of stroke and ischaemic heart disease. Methods The present analyses involved 409,156 adults in the China Kadoorie Biobank study without a prior history of coronary heart disease or stroke or insomnia symptoms. The mean age of study participants was 52 years and 59% were women. Self-reported sleep duration including daytime napping was recorded using a questionnaire. The adjusted hazard ratios (HRs) for disease outcomes associated with sleep duration were estimated by Cox proportional hazards after adjustment for confounding factors. Results The overall mean (SD) sleep duration was 7.4 (1.4) hours. The associations of sleep duration with CVD types were U-shaped, with individuals reporting 7–8 h of sleep having the lowest risks. Compared with those who typically slept 7–8 h, individuals with very short sleep duration (≤ 5 h) had adjusted HRs of 1.10 (95% CI 1.04–1.16), 1.07 (1.01–1.13), 1.19 (1.06–1.33) and 1.23 (1.10–1.37) for total stroke, ischaemic stroke (IS), Intracerebral haemorrhage (ICH) and major coronary events (MCE), respectively. Likewise, individuals with very long sleep duration (≥ 10 h) had HRs of 1.12 (1.07–1.17), 1.08 (1.03–1.14), 1.23 (1.12–1.35) and 1.22 (1.10–1.34) for the same diseases, respectively, with little differences by sex and age. The patterns were similar for all-cause mortality. Conclusions While abnormal sleep duration (≤ 6 h or ≥ 9 h) was associated with higher risks of CVD, the risks were more extreme for those reporting ≤ 5 or ≥ 10 h, respectively and such individuals should be prioritised for more intensive treatment for CVD prevention