Scientists followed the drinking and smoking habits of 22,524 people in the United Kingdom who were between the ages of 39 and 79 and did not have a history of heart attack or stroke at the start of the study. During the 12-year study, 864 strokes occurred.
The study found that the association between alcohol drinking and stroke was significantly different between smokers and non-smokers. In non-smokers, people who consumed moderate amounts of alcohol were 37 percent less likely to develop stroke than non-drinkers, while in smokers this association was not observed.
This finding suggests that smoking may modify the relationship between alcohol intake and stroke risk. Moderate drinking was defined as consuming up to 21 units of alcohol per week, which is equal to about two to three regular glasses of red wine a day.
"Our findings could have public health implications in that we appear to have a clearer understanding of the dangers of combining smoking and moderate drinking on overall stroke risk," according to Yangmei Li, MPhil, with the University of Cambridge in the United Kingdom.
"While heavy alcohol consumption is considered to increase the risk of stroke, the relationship between light to moderate drinking and stroke has varied considerably among studies," said Li. "It's possibly these conflicting results could be explained by the interaction between cigarette smoking and alcohol on stroke risk." This reinforces the evidence that smoking not only increases stroke risk on its own but may additionally affect adversely how other lifestyle factors may relate to stroke risk.