Introduction:
Short or long sleep hours are associated with adverse health outcomes, including diabetes, hypertension, coronary heart disease (CHD) and total mortality. However, the prospective relation between sleep duration and stroke risk is less studied, particularly in Asians. Thus, we assessed the hypothesis that short (≤5 hours) and long (≥9 hours) sleep durations were related to increased risk of stroke mortality among Chinese adults residing in Singapore.
Methods:
The Singapore Chinese Health Study is a population-based cohort that recruited 63,257 Chinese adults aged 45-74 years during 1993 and 1998. Sleep duration was assessed at baseline and categorized to five groups: ≤5, 6, 7, 8 or ≥9 hours. Death information was identified via registry linkage up to December 31, 2011, with ICD-9 codes 430-438 for all stroke deaths, 430-432 for hemorrhagic, and 433-438 for ischaemic or non-specified stroke deaths. Cox proportional hazard models were used to calculate hazard ratios (HRs) with adjustment for socio-demographic, lifestyle and comorbidities.
Results:
We documented 1,381 total stroke deaths (322 hemorrhagic and 1,059 ischaemic or non-specified strokes) during 926,752 person-years of follow-up. Compared to the reference group of sleeping for 7 hours, the multivariate-adjusted HR (95% confidence interval) for total stroke mortality was 1.25 (1.05-1.50) for ≤5 hours, 1.01 (0.87-1.18) for 6 hours, 1.09 (0.95-1.26) for 8 hours, and 1.54 (1.28-1.85) for ≥9 hours. The increased risk was also observed for ischaemic or non-specified stroke deaths with short (1.37; 1.12-1.68) and long (1.68; 1.36-2.06) sleep durations, but not for hemorrhagic stroke deaths (0.92 [0.62-1.36] and 1.14 [0.76-1.72], respectively). We observed significant interaction with baseline hypertension (P-interaction=0.04): positive association was found for short (1.54; 1.16-2.03) and long (1.95; 1.48-2.57) sleep durations among individuals with baseline hypertension, but not among those without baseline hypertension (1.07 [0.85-1.36] and 1.27 [0.98-1.63], respectively). Furthermore, in participants without baseline CHD/stroke, short and long sleep durations were related to an increased risk (HR 1.30 [1.07-1.57] and 1.43 [1.16-1.76], respectively); while in CHD/stroke patients, only long sleep duration was associated with an increased risk (2.34; 1.53-3.57), but not the short sleep duration (0.96; 0.57-1.62).
Conclusions:
In this large cohort study of Chinese adults, both short and long sleep durations were significantly associated with increased risks of stroke mortality. The associations were significant and stronger in hypertensive participants, but not in those without hypertension. Further studies are needed to confirm the interaction with hypertension and explore the mechanisms linking sleep quantity and stroke mortality.
Association between prediagnostic leukocyte telomere length and breast cancer risk: the Singapore Chinese Health Study
