Blood Pressure and Risk of Subarachnoid Hemorrhage in China

McGurgan, IJ; Clarke, R; Lacey, B; Kong, XL; Chen, ZM; Chen, YP; Guo, Y; Bian, Z; Li, LM; Lewington, S

Clarke, R (reprint author), Univ Oxford, Big Data Inst, Nuffield Dept Populat Hlth, Old Rd Campus, Oxford OX3 7LF, England.

STROKE, 2019; 50 (1): 38

Abstract

Background and Purpose Subarachnoid hemorrhage (SAH) has a high case fatality rate and young mean age at onset compared with other types of stroke, but the pathogenesis of SAH is not fully understood. We examined associations of systolic and diastolic blood pressure with incident nontraumatic SAH in a large prospective study in China. Methods In 2004 to 2008, 512891 adults (59% women) from the general population were recruited into the CKB study (China Kadoorie Biobank). Participants were interviewed, measured, and followed up for fatal and nonfatal events. After excluding those with prior vascular disease, Cox regression analysis was used to relate blood pressure to incident SAH events. Analyses were adjusted for major confounders and corrected for regression dilution to give associations with long-term average blood pressure. Results At baseline, mean age was 51 (SD, 11) years, and mean systolic blood pressure/diastolic blood pressure was 130.6/77.6 (SD, 21.0/11.1) mmHg. During 3.5 million person-years of follow-up, there were 553 incident SAH cases (mean age at event, 61 [SD, 11] years), yielding an overall annual incidence rate of 12.9 per 100000. Higher average levels of blood pressure were linearly and positively associated with higher risks of incident SAH: a 10 mmHg higher systolic blood pressure and a 5 mmHg higher diastolic blood pressure were associated with hazard ratios for SAH of 1.21 (95% CI, 1.13-1.29) and 1.20 (95% CI, 1.12-1.28), respectively. There was no evidence that the hazard ratios varied by age or sex or by levels of other vascular risk factors. Elevated blood pressure (systolic blood pressure, >120 mmHg) accounted for 23% of all SAH cases. Conclusions The incidence of SAH in China was comparable with estimates from Western populations. Higher levels of blood pressure were positively associated with higher risks of SAH, and elevated blood pressure accounted for about a quarter of all SAH cases.

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