Sex-Specific Associations of Smoking with Spontaneous Subarachnoid Hemorrhage: Findings from Observational Studies

Abstract Background Some studies have reported that women are at higher risk for spontaneous subarachnoid hemorrhage (SAH) compared with men, and smoking is the most important lifestyle risk factor for spontaneous SAH. However, it is still unknown whether the risk of SAH from smoking and smoking status is differential for women and men. We performed a meta-analysis to estimate the effect of smoking on SAH in women compared with men. Methods PubMed (January 1, 1966 to February 19, 2020) and EMBASE (January 1, 1980 to February 19, 2020) were systematically searched. Studies that estimated sex-specific relative risks (RRs) of SAH were selected. We pooled sex-specific RRs, comparing women with men using random-effects meta-analysis. Results Data from 20 observational studies that included 1,387,204 participants (563,898 women) and 7,838 SAHs (3,977 women) were analyzed. The combined women-to-men RRs of former smokers versus never smokers for SAH were 1.08 (95% confidence interval [CI] 0.62–1.89, p = 0.78). The pooled women-to-men RRs of current smokers versus never smokers were 1.39 (95% CI 1.05–1.83, p = 0.02). The combined women-to-men RRs of total smokers versus never smokers RRs were 1.15 (95% CI 0.88–1.52, p = 0.30). Conclusions Our study shows there is not enough evidence to suggest that women who smoke have a greater risk for SAH than men; however, women who persistently smoke have a greater risk. Smoking seems to be more susceptible in the increased SAH risk in women.