MONDAY, Oct. 1 (HealthDay News) -- For older people with heart disease or advanced diabetes, moderate drinking may increase their risk of a heart rhythm disorder called atrial fibrillation, according to a new study.

Atrial fibrillation is a quivering or irregular heartbeat that affects about 2.7 million people in the United States, and is a risk factor for stroke.

Researchers analyzed data from more than 30,000 people, aged 55 and older, in 40 countries who had a history of cardiovascular disease or advanced diabetes with organ damage.

Moderate to high alcohol intake was associated with an increased risk of atrial fibrillation. And for moderate drinkers, the effect of binge drinking was similar to that of habitual heavy drinking, according to the study, which was published Oct. 1 in CMAJ, the journal of the Canadian Medical Association

Moderate drinking was defined as up to two drinks per day or one to 14 drinks per week for women. For men, moderate drinking was three drinks per day or one to 21 drinks per week. Binge drinking was defined as five or more drinks in a day, regardless of whether someone was usually a low, moderate or heavy drinker.

Nearly 79 percent of binge drinkers were in the moderate alcohol-consumption group.

During a nearly five-year follow-up, about 2,100 new cases of atrial fibrillation were diagnosed in the study participants. The incidence rate per 1,000 "person-years" was 14.5 among light drinkers (up to one drink per week), 17.3 among moderate drinkers and 20.8 among heavy drinkers (more than two drinks a day for women and more than three per day for men).

"Because drinking moderate quantities of alcohol was common in our study (36.6 percent of the participants), our findings suggest that the effect of increased alcohol consumption, even in moderate amounts, on the risk of atrial fibrillation among patients with existing cardiovascular disease may be considerable," wrote Dr. Koon Teo, of McMaster University in Hamilton, Ontario, and colleagues in a university news release.

Some research has suggested that moderate alcohol consumption may benefit the heart, a journal news release noted.

"Recommendations about the protective effects of moderate alcohol intake in patients at high risk of cardiovascular disease may need to be tempered with these findings," the study authors concluded.

Although the study found a link between moderate drinking and atrial fibrillation, it did not prove cause-and-effect.

More information

The American Heart Association has more about alcohol and heart disease.