Searching for the smoker's paradox in acute stroke patients treated with intravenous thrombolysis
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Background: Inconsistent evidence supports better outcome in smokers after stroke. Our study examines this association in a large sample of ischemic stroke treated with intravenous thrombolysis. Method: Virtual International Stroke Trials Archive (VISTA) database, composed of individual patient data of multiple clinical trials, was queried. The primary outcome was functional independence at 3 months noted by modified Rankin Scale (mRS; a 7-point scale ranging from 0 [no deficit] to 6 [death]) score= 2. The secondary outcomes were National Institutes of Health Stroke Scale (NIHSS; stroke severity measure, ranging from 0 [no deficit] to 42 [most severe]) score at 24 hours and the occurrence of symptomatic intractracranial hemorrhage. Results: A total of 5383 patients were included: 1501 current smokers and 3882 nonsmokers. Smokers were younger (60 +/- 13 vs. 71 +/- 12 years, p < .0001) and had lower median NIHSS score at baseline (12 [8-17] vs. 13 [9-18], p < .0001). The rate of favorable functional outcome (mRS = 2) at 3 months was significantly higher among current smokers (49.7% vs. 39.5%, p < .0001) and with crude ORs of 1.52, 95% CI 1.33-1.72. The association became non-significant after adjusting for age (OR 1.11, 95% CI 0.97-1.27). Subgroup analysis by age/gender strata showed that current smoking was associated with favorable outcome only in women >/= 65 years. Current smoking was also associated with lower rates of symptomatic intracranial hemorrhage (adjusted OR 0.55, 95% CI 0.39-0.79). Conclusion: Smokers experience their first ever stroke 11 years younger than nonsmokers. This age difference explains the association between current smoking and favorable functional outcome. Implications: Smoking is associated with occurrence of first ever stroke at a younger age, therefore, focus should be on smoking prevention and treatment. The decision to treat ischemic stroke patients with intravenous thrombolysis should not be influenced by the patients' smoking status.
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