SUBARACHNOID HEMORRHAGE AND FAMILY HISTORY - A POPULATION-BASED CASE-CONTROL STUDY

Objective: To evaluate family history as a risk factor for subarachnoid hemorrhage. Design and Setting: A population-based case-control study in King County, Washington. Subjects: Cases consisted of 149 patients with spontaneous subarachnoid hemorrhage. Two control subjects who were matched to cases by gender and age within 5 years were identified for each case using random digit telephone dialing. Main Measure: Detailed information on family history was obtained through an in-person interview. Results: Some 11.4% of cases had a first-degree relative with a history of subarachnoid hemorrhage, compared with 6.4% of controls, yielding an odds ratio of 1.8 (95% CI, 0.92 to 3.7). The odds ratio for a positive family history among other relatives was 2.4 (95% CI, 1.1 to 5.2), likely reflecting family information bias. Findings were similar after adjustment was made for potential confounding variables, including cigarette smoking, a history of hypertension, and number of siblings and children. Conclusion: Although familial factors may be important in some families, overall they account for few cases of subarachnoid hemorrhage.