Association of smoking with high-risk characteristics for rupture of unruptured intracranial aneurysms

Smoking is a known risk factor for growth and rupture of unruptured intracranial aneurysms (UIAs). We aimed to determine whether smoking is associated with aneurysm characteristics that increase the risk of rupture. In a multicenter cross-sectional study, we included adult patients with one or more UIAs. Patients with an unknown smoking status were excluded. We categorized smoking status into current, former and never smokers and calculated odds ratios (ORs) with 95% confidence intervals (95%CIs) for aneurysm characteristics between smoking categories. We adjusted for age, previous subarachnoid hemorrhage from another aneurysm, and hypertension, and performed stratified analyses by sex. Of 1180 patients with 1795 aneurysms, 561 smoked at time of aneurysm detection, 359 had quit smoking >3 months before aneurysm detection, and 260 had never smoked. The adjusted ORs comparing ever to never smokers were for larger size (≥7 mm) 1.62 (95%CI 1.21-2.18), for multiplicity 1.26 (95%CI 0.92-1.75), for irregular morphology 1.29 (95%CI 0.94-1.78) and for location other than internal carotid or middle cerebral artery 1.14 (95%CI 0.86-1.53). The adjusted ORs comparing current versus never smokers were for larger size 1.77 (95%CI 1.29-2.45) and for multiplicity 1.57 (95%CI 1.12-2.21). For every 10 pack-years in ever smokers the adjusted ORs for aneurysm multiplicity were 1.11 (95%CI 1.02-1.20), in current smokers 1.17 (95%CI 1.03-1.34); for larger size in current smokers 1.14 (95%CI 1.00-1.30). Smoking is associated with larger and multiple UIAs in a dose-dependent fashion. These observations may contribute to understanding the higher risk of rupture of UIAs in smokers.