Smoking and elevated blood pressure are the most important risk factors for subarachnoid hemorrhage in the Asia-Pacific region: an overview of 26 cohorts involving 306,620 participants.
OBJECTIVE
The cause of subarachnoid hemorrhage (SAH) is poorly understood and there are few large cohort studies of risk factors for SAH. We investigated the risk of SAH mortality and morbidity associated with common cardiovascular risk factors in the Asia-Pacific region and examined whether the strengths of these associations were different in Asian and Australasian (predominantly white) populations.


METHODS
Cohort studies were identified from Internet electronic databases, searches of proceedings of meetings, and personal communication. Hazard ratios (HRs) for systolic blood pressure (SBP), current smoking, total serum cholesterol, body mass index (BMI), and alcohol drinking were calculated from Cox models that were stratified by sex and cohort and adjusted for age at risk.


RESULTS
Individual participant data from 26 prospective cohort studies (total number of participants 306,620) that reported incident cases of SAH (fatal and/or nonfatal) were available for analysis. During the median follow-up period of 8.2 years, a total of 236 incident cases of SAH were observed. Current smoking (HR, 2.4; 95% CI, 1.8 to 3.4) and SBP >140 mm Hg (HR, 2.0; 95% CI, 1.5 to 2.7) were significant and independent risk factors for SAH. Attributable risks of SAH associated with current smoking and elevated SBP (> or =140 mm Hg) were 29% and 19%, respectively. There were no significant associations between the risk of SAH and cholesterol, BMI, or drinking alcohol. The strength of the associations of the common cardiovascular risk factors with the risk of SAH did not differ much between Asian and Australasian regions.


CONCLUSIONS
Cigarette smoking and SBP are the most important risk factors for SAH in the Asia-Pacific region.
Feigin
Valery
V
Department of Medicine and School of Population Health, Faculty of Medicine and Health Sciences, University of Auckland, Auckland, New Zealand. v.feigin@ctru.auckland.ac.nz
Parag
Varsha
V
Lawes
Carlene M M
CM
Rodgers
Anthony
A
Suh
Il
I
Woodward
Mark
M
Jamrozik
Konrad
K
Ueshima
Hirotsugu
H
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001208:Asia; D001315:Australia; D001794:Blood Pressure; D015992:Body Mass Index; D001921:Brain / Q000473:pathology; D002318:Cardiovascular Diseases / Q000401:mortality*; D015331:Cohort Studies; D019992:Databases as Topic; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications*; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012044:Regression Analysis; D012306:Risk; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis* / Q000209:etiology* / Q000473:pathology; D013997:Time Factors