Influence of premorbid factors on survival following subarachnoid hemorrhage

OBJECT: The goal of this study was to explore the relationships between premorbid patient characteristics, especially cigarette smoking, and the risk of death following subarachnoid hemorrhage (SAH). METHODS: A population-based study design was used with multiple overlapping methods of case identification. A strict definition of SAH was used. Relationships between patients' age and sex as well as their cigarette smoking and hypertension statuses were explored by calculating relative risks (RRs). Confounding effects were examined using logistic regression analysis. The author identified 800 cases in which the patient had experienced his or her first SAH. Seventy-seven percent of cases were verified by review of computerized tomography scans, 22% by autopsy, and 1% by lumbar puncture. A prior history of hypertension had no effect on the risk of mortality. There was a higher case mortality rate in female patients than in male patients, but this did not reach statistical significance. The RR of death at 30 days post-SAH for patients older than 60 years compared with those who were younger was 2.95 (95% confidence interval [CI] 2.18-3.97). The RR of death at all time intervals was lower for smokers than for nonsmokers (smokers/nonsmokers RR 0.47 [95% CI 0.32-0.69] at 7 days). The protective effect of smoking diminished on Day 3 post-SAH and increased again on Day 7. CONCLUSIONS: Advanced age is an important determinant of survival following SAH. Smoking appears to have a protective effect. The author presents evidence indicating that increased vasospasm in smokers may reduce the severity of the initial hemorrhage.