Cigarette smoking, hypertension and the risk of subarachnoid hemorrhage: a population-based case-control study.

A case-control analysis is used to examine the relation of cigarette smoking, hypertension and the risk of subarachnoid hemorrhage in men and women aged 35-64 years. 45 men and 70 women with subarachnoid hemorrhage were identified as part of a large community based study of stroke, and the controls, 1017 men and 569 women, came from a survey of cardiovascular risk factors conducted in the same community. Cigarette smokers, after adjusting for age, had a significantly increased risk of subarachnoid hemorrhage compared with nonsmokers with relative risks of 3.0 for men and 4.7 for women. The strength of the risk increased with the amount smoked. The association remained significant for each sex after adjusting for hypertension. Those who both smoked and had a history of hypertension had an increased risk of subarachnoid hemorrhage of almost 15 fold compared to those who neither smoked nor had been treated for hypertension. The estimated population attributable risk of subarachnoid hemorrhage associated with cigarette smoking (43%) was greater than that of hypertension (28%) in this population.