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.