Women who consume more than two alcoholic drinks a day have a higher risk of getting the most common type of heart rhythm disturbance, which can raise the chances of having a stroke, researchers said on Tuesday.
Previous research had shown that men who drink three or more alcoholic beverages daily have an elevated risk for atrial fibrillation, but the risk for women had not been clear.
Researchers in the United States and Switzerland tracked 34,715 middle-aged American women for more than 12 years who did not have atrial fibrillation at the outset of the study.
There was no increased risk for the vast majority who drank either no alcohol or less than two drinks daily. But those who drank more had a 60 percent increased risk for atrial fibrillation.
The condition occurs when the heart's two upper chambers beat quickly and irregularly. Because blood is not pumped completely from the heart's upper chambers, it can pool and clot. If a piece of one of these clots becomes lodged in an artery in the brain, a stroke occurs.
U.S. Vice President Dick Cheney, who has a history of heart problems, was treated for atrial fibrillation in October.
"Small to moderate amounts of alcohol -- up to two drinks a day -- do not appear to be associated with an increased risk," said Dr. Christine Albert of Brigham and Women's Hospital and Harvard Medical School, one of the researchers in the study published in the Journal of the American Medical Association.
"But if you do drink more than two drinks a day and you're looking for a way to decrease your risk of atrial fibrillation, it may be that reducing alcohol consumption may be helpful."
Only about 4 percent of the women in the study reported drinking that much.
Albert said in a telephone interview the study's design does not allow the researchers to state with certainty that the drinking caused the increased risk. This level of drinking may signal an overall less-healthy lifestyle, she said.
"Most of the studies that have looked at alcohol and atrial fibrillation were done primarily in men. So we had wanted to look at it in women because relationships could be different, but also women drink different amounts of alcohol than men and have different drinking patterns," Albert said.