Pavla Kadlecová, a statistician at the International Clinical Research Center of St. Anne's University Hospital in the Czech Republic, and colleagues analysed data from the Swedish Twin Registry of 11,644 same-sex twins who answered questionnaires in 1967-1970. All the twins were under the age of 60 when they completed the dietary questionnaires, from which researchers could gather information on their alcohol consumption.
The twins were followed for around 43 years, until 2010. Kadlecová et al. analysed their health data over this period, including hospital discharge information and details on causes of death, as well as information on blood pressure, diabetes and smoking, among other health risks.
During the follow-up period, about 30 percent of participants had a stroke. The investigators divided the participants into three groups based on their alcohol consumption at study baseline: "light" drinkers (half an alcoholic drink a day), "moderate" drinkers (up to two drinks a day) and "heavy" drinkers (more than two drinks a day). These definitions for alcohol consumption are in line with recommendations from the AHA: about 8 ounces of wine (two drinks) for a man and 4 ounces (one drink) for a woman.
Kadlecová et al.'s analysis indicated that:
- Heavy drinkers had about a 34 percent higher risk of stroke compared to light drinkers.
- Twins who engaged in heavy drinking in their 50s and 60s were more likely to suffer a stroke five years earlier than those who were light drinkers. This indicates that heavy alcohol consumption during middle age raises stroke risk independently of genetic and early-life factors.
- Heavy drinkers had increased stroke risk in their midlife compared to well-known risk factors like high blood pressure and diabetes.
- At age 75 and over, blood pressure and diabetes appeared to take over as one of the main influences on having a stroke.
High blood pressure (hypertension), diabetes, smoking and high cholesterol are among the major, well-known risk factors for stroke. Previous studies have indicated that heavy alcohol use is also an important risk factor for stroke, but Kadlecová et al. said their study is the first to look at how this risk varies by 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. For mid-aged adults, avoiding more than two drinks a day could be a way to prevent stroke in later productive age (about 60s)," Kadlecová noted.
Co-authors of the study are Ross Andel, PhD; Robert Mikulik, PhD; Elizabeth Handing, BA; and Nancy Pedersen, PhD. The study was supported by the European Regional Development Fund.
Source: American Heart Association
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