Drinking more than two alcoholic beverages a day in middle-age can raise risk of stroke more than traditional factors such as high blood pressure and diabetes, a new long-term study has warned.
In the study of 11,644 middle-aged Swedish twins who were followed for 43 years, researchers compared the effects of an average of more than two drinks daily ("heavy drinking") to less than half a drink daily ("light drinking").
The study found that heavy drinkers had about a 34 per cent higher risk of stroke compared to light drinkers.
Researchers found that mid-life heavy drinkers (in their 50s and 60s) were likely to have a stroke five years earlier in life irrespective of genetic and early-life factors.
Heavy drinking increased stroke risk during mid-life more than any other risk factor, but blood pressure and diabetes became more significant at around age 75.
Past studies have shown that alcohol affects stroke risk, but this is the first study to pinpoint differences with age.
"We now have a clearer picture about these risk factors, how they change with age and how the influence of drinking alcohol shifts as we get older," said Pavla Kadlecova, a statistician at St Anne's University Hospital's International Clinical Research Center in the Czech Republic.
Researchers analysed results from the Swedish Twin Registry of same-sex twins who answered questionnaires in 1967-70. All twins were under age 60 at the start.
By 2010, the registry yielded 43 years of follow-up, including hospital discharge and cause of death data.
Researchers then sorted the data based on stroke, high blood pressure, diabetes and other cardiovascular incidents.
Almost 30 per cent of participants had a stroke. They were categorised as light, moderate, heavy or non-drinkers based on the questionnaires.
Researchers compared the risk from alcohol and health risks like high blood pressure, diabetes and smoking.
Among identical twin pairs, siblings who had a stroke drank more than their siblings who hadn't had a stroke, suggesting that mid-life drinking raises stroke risks regardless of genetics and early lifestyle.
The research is published in the American Heart Association journal Stroke.
