Prestroke smoking status affects functional outcomes after acute ischemic stroke
Smoking Status and Functional Outcomes After Acute Ischemic Stroke
Introduction and methods
It is well-established that cigarette smoking increases the risk of stroke, and that this risk increases with a higher number of cigarettes [1-4]. Furthermore, smoking has detrimental effects on poststroke long-term outcomes [2,5]. It has been shown that cessation of smoking decreases the risk of stroke and reduces the risks of stroke recurrence and death during follow-up periods [6-8]. Less is known about the effect of smoking before stroke onset on short-term functional outcomes after stroke. Some reports even described that nicotine may have a neuroprotective role in some central nervous system dysorders [9-11]. This study focused on the effect of smoking status and poststroke functional outcomes at 3 months after acute ischemic stroke.
This multicenter stroke registry study investigated functional outcomes in 10,285 patients with acute ischemic stroke. Mean age was 70.2±12.2 years and 37.0% were women. Patients were asked about their smoking status and then categorized according to smoking status: current smokers (smoking at the time of stroke onset, 24.9%, n=2561), former smokers (stopped smoking more than half year before stroke onset, 32.4%, n=3328) and nonsmokers (patients who never smoked, 42.7%, n=4396). Number of cigarettes per day and number of years spend smoking were additionally asked. Smoking index (number of cigarettes smoked daily x number of years spend smoking) was calculated for each current smoker. Former smokers were categorized into groups according to the number of years between smoking cessation and stroke onset: ≤2, 3 to 5, 6 to 10, 11 to 20 and ≥20 years.
Study outcomes were poor functional outcome (modified Rankin Scale [mRS] score 2 to 6) and functional dependence (mRS score 2 to 5, excluding death) at 3 months after stroke.
- Multivariate-adjusted ORs of poor functional outcome (OR: 1.25, 95%CI 1.08-1.45, P=0.003) and functional dependence (OR:1.29, 95%CI 1.11-1.49, P=0.001) were significantly higher in current smokers compared to nonsmokers. No significant differences in functional outcomes were found between former smokers and nonsmokers.
- Multivariate-adjusted ORs for the functional outcomes increased significantly with increasing number of smoked cigarettes per day (P-trend=0.002 for poor functional outcome and P-trend<0.001 for functional dependence). In addition, a significant association was found between smoking index and both poor functional outcome and functional dependence.
- Poor functional outcome and functional dependence were significantly higher in former smokers who stopped smoking within 2 years of stroke onset compared to non-smokers (multivariate-adjusted OR: 1.75, 95%CI 1.15-2.66, P=0.008 for poor functional outcome and multivariate-adjusted OR: 1.71, 95%CI 1.01-1.50, P=0.01 for functional dependence). No significant differences in functional outcomes were found between former smokers who stopped smoking longer than 2 years ago and nonsmokers.
- Neurological improvement was not significantly different in the three different smoking status groups.
This registry study showed that patients who smoked at the time of stroke onset had a significantly increased risk of poor functional outcome and functional dependence at 3 months after acute ischemic stroke compared to patients who did not smoke. Risk of unfavorable outcomes increased with increasing number of cigarettes per day and smoking index. Patients who stopped smoking within 2 years of stroke onset also had a higher risk of poor functional outcome and functional dependence. The risk of poststroke unfavorable functional outcomes did not statistically differ between former smokers who stopped smoking longer than 2 years before stroke onset and nonsmokers.