Stroke incidence in women under 60 years of age related to alcohol intake and smoking habit.

BACKGROUND AND PURPOSE: The association between alcohol intake, cigarette smoking and risk of stroke amongst women remains unclear, especially in young women.

METHODS: This prospective cohort study included 45,449 Swedish women aged 30-50 years free of stroke and heart diseases at enrollment in 1991 and 1992. Information on drinking and smoking habits at enrollment was collected using a questionnaire. Incident stroke cases were identified through cross-linkage to the Swedish Inpatient Register. Cox proportional hazards regression models were used to calculate relative risks (RR) and their corresponding 95% confidence intervals (CIs).

RESULTS: During an average of 11 years of follow-up, 170 incident stroke cases, of which 111 ischemic and 47 hemorrhagic, were identified. Compared to abstainers, risk of stroke was reduced among women consuming less than 20 g (RR = 0.7, 95% CI 0.5-1.0) or 20-69.9 g (RR = 0.5, 95% CI 0.3-0.7) of alcohol per week, whilst women who consumed > or =70 g of alcohol per week had a nonsignificant reduced relative risk (RR = 0.7, 95% CI 0.4-1.3). We found no difference in stroke risk according to the types of alcoholic beverage consumed. Compared with never smokers, there was an increased risk of all strokes among current smokers of 1-9 cigarettes/day (RR = 2.3, 95% CI 1.5-3.7) or > or =10 cigarettes/day (RR = 2.6, 95% CI 1.7-4.1). The observed smoking-related excess risks were confined mainly to ischemic stroke. Former smokers had a 50-60% increase in RRs of both ischemic and hemorrhagic stroke. In stratified analyses, current smokers had a 4-fold excess risk if they were nondrinkers (RR = 4.2; 95% CI 2.2-7.8) but a lower risk (RR = 1.5; 95% CI 0.8-2.4) if they drank in moderation. Compared to never drinkers and never smokers, women who drank in moderation were also at reduced risk (RR = 0.6; 95% CI 0.3-1.1). These interactions were statistically significant (p = 0.001).

CONCLUSIONS: Light to moderate alcohol intake, regardless of type of alcoholic beverage, reduces risk of stroke among women under 60 years of age, in particular those women who were never smokers. Smoking increases the risk of stroke, especially ischemic stroke.