Cigarette smoking and subarachnoid haemorrhage: a population-based case-control study.

Smoking habits were analysed in 114 patients with subarachnoid haemorrhage, less than 70 years old, obtained from an epidemiological study. One control, matched for age, sex, and domicile, was selected for each patient. Current cigarette smokers were significantly more prevalent among cases than controls, and the relative risk of subarachnoid haemorrhage compared with non-smokers was 2.7 in men and 3.0 in women. The so called metastatic emphysema theory with increased elastolytic activity in the serum of smokers is proposed as biochemical basis for the increased risk of subarachnoid haemorrhage.