Rautalin I, Kaprio J, Ingebrigtsen T, et al. - The earlier documented inverse link between body mass index (BMI) and the risk of subarachnoid hemorrhage (SAH) seems to be at least partly explained by smoking and hypertension, the most important risk factors of SAH. Thus, a likely modest independent role of BMI in the risk of SAH is suggested.

• In various population-based cohort studies, a reduced risk of SAH has been linked to a higher BMI.

• Data from 211,972 adult participants were integrated from three prospective population-based Nordic cohorts, and SAH risk was compared between three BMI categories (low (BMI<22.5), moderate (BMI: 22.5–29.9), and high (BMI≥30) BMI).

• Relative to moderate BMI, an increased risk for SAH (adjusted hazard ratio [HR], 1.30) was observed in those with low BMI, whereas no significant risk difference was identified in high BMI category (HR, 0.91).

• However, the elevated risk of low BMI was only identified in smokers (HR, 1.49) and in hypertensive men (HR, 1.72).