Background and Purpose—Smoking is an established risk factor for stroke; however, it is uncertain whether prestroke smoking status affects clinical outcomes of acute ischemic stroke. This study aimed to elucidate the association between smoking status and functional outcomes after acute ischemic stroke. Methods—Using a multicenter hospital-based stroke registry in Japan, we investigated 10 825 patients with acute ischemic stroke hospitalized between July 2007 and December 2017 who had been independent before stroke onset. Smoking status was categorized into those who had never smoked (nonsmokers), former smokers, and current smokers. Clinical outcomes included poor functional outcome (modified Rankin Scale score ≥2) and functional dependence (modified Rankin Scale score 2–5) at 3 months. We adjusted for potential confounding factors using a logistic regression analysis. Results—The mean age of patients was 70.2±12.2 years, and 37.0% were women. There were 4396 (42.7%) nonsmokers, 3328 (32.4%) former smokers, and 2561 (24.9%) current smokers. The odds ratio (95% CI) for poor functional outcome after adjusting for confounders increased in current smokers (1.29 [1.11–1.49] versus nonsmokers) but not in former smokers (1.05 [0.92–1.21] versus nonsmokers). However, among the former smokers, the odds ratio of poor functional outcome was higher in those who quit smoking within 2 years of stroke onset (1.75 [1.15–2.66] versus nonsmokers). The risk of poor functional outcome tended to increase as the number of daily cigarettes increased in current smokers (P for trend=0.002). All these associations were maintained for functional dependence. Conclusions—Current and recent smoking is associated with an increased risk of unfavorable functional outcomes at 3 months after acute ischemic stroke.
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