Lung function as a risk factor for subarachnoid hemorrhage: a prospective cohort study.

BACKGROUND AND PURPOSE: The etiology of subarachnoid hemorrhage (SAH) is poorly understood. Reduced lung function, expressed as low forced expiratory volume in 1 second (FEV(1)) and low forced vital capacity (FVC), is a predictor of cardiovascular disease, but whether reduced lung function is a risk factor for SAH is not known. The association between lung function and incidence of SAH was investigated in a prospective cohort study. METHODS: Between 1974 and 1992, 20 534 men and 7237 women (mean age, 44 years) were examined in a health screening program including spirometry. The incidence of SAH was studied during a mean follow-up of 26 years in relation to age- and height-standardized FEV(1), FVC, and FEV(1)/FVC. RESULTS: One hundred forty-five subjects had a SAH (18.3 per 100 000 person-years in men and 26.5 per 100 000 person-years in women). The hazard ratio for SAH in the lowest compared to the highest quartile of FEV(1) and FEV(1)/FVC was 2.24 (95% CI, 1.32-3.81; P for trend=0.014) and 1.92 (95% CI, 1.14-3.23; P for trend=0.003), respectively, after adjustment for several confounding factors including smoking and hypertension. The results persisted when analysis was restricted to nonsmokers. FVC showed no significant association with incidence of SAH. CONCLUSIONS: Baseline lung function, expressed as low FEV(1) or FEV(1)/FVC, is a risk factor for SAH, independently of smoking.