Moderate drinking linked to abnormal heart rhythm

People with heart disease who drink, even moderately, may have a slightly increased risk of a common heart rhythm problem, a new study suggests.

The study is not the first to link moderate drinking to the heart arrhythmia, known as atrial fibrillation (AF). But it's still not clear that the habit, itself, is the problem.

Doctors have long known that a drinking binge can trigger an episode of AF, in which the heart's upper chambers begin to quiver chaotically instead of contracting normally.

Things get murky, though, when it comes to moderate drinking.

In general, it's thought that having one or two drinks per day is protective against coronary heart disease - where cholesterol-containing "plaque" builds up in the arteries.

But modest drinking hasn't been linked to a decreased risk of AF - and the new findings suggest that when people already have heart issues, moderate drinking is actually tied to more AF cases.

The study, reported in the Canadian Medical Association Journal, included more than 30,000 older adults who either had clogged arteries, a history of stroke or diabetes complications such as kidney disease. Most had coronary heart disease.

Over about five years, people who drank occasionally or not at all developed AF at a rate of about 1.5 percent each year. For moderate drinkers, the rate was 1.7 percent, and for heavy drinkers, it was 2.1 percent.

The researchers looked at other factors, too - like age, weight and smoking habits. But moderate drinking was still linked to a 14-percent increase in the risk of AF.

"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," write the researchers, led by Dr. Yan Liang, of McMaster University in Hamilton, Ontario.

Still, a researcher not involved in the work doubted the link between moderate drinking and AF.

One problem is separating out the effects of binge drinking, according to Dr. Kenneth J. Mukamal, of Harvard University and Beth Israel Deaconess Medical Center in Boston.

Liang and colleagues did do a separate analysis where they excluded people who reported a history of binge drinking - having more than five drinks at a time. And the results were similar.

But, Mukamal said in an email, the study did not repeatedly measure binge drinking habits over the five-year follow-up. So it's impossible to know if moderate drinkers' AF episodes were related to binges.

"The majority of binge-drinking episodes nationwide occur among otherwise moderate drinkers," Mukamal noted.

What's more, he said, the current study included patients who were involved in two clinical trials testing blood pressure drugs.