January 20, 2011

Heavy Drinkers At Risk Of Heart-rhythm Disturbance

People who drink alcohol on a regular basis, especially those who are considered heavy drinkers, might be more likely to suffer the common heart-rhythm disturbance atrial fibrillation (AF) than those who abstain from intoxicating drinks, according to suggestions from a new research review.

Based on the analysis of 14 separate studies, researchers found that the heaviest drinkers were more likely to be diagnosed with AF than those who drank little to no alcohol.

The studies differed in what "heavy drinking" meant. For the minimum, it meant two or more drinks per day for men, and one or more per day for women. In some of the studies, heavy drinking was defined as having at least six drinks per day.

When all the results were combined, researchers found that heavy drinkers were 51 percent more likely to suffer AF than both non-drinkers and occasional drinkers.

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

But the new findings suggest that people's chronic drinking habits may also matter, according to the researchers, led by Dr. Satoru Kodama of the University of Tsukuba Institute of Clinical Medicine in Ibaraki, Japan.

"What we revealed in the current (study) is that not only episodic but habitual heavy drinking is associated with higher risk of AF," co-researcher Dr. Hirohito Sone told Reuters Health by email.

But the study also found evidence linking fairly moderate drinking to a higher risk of AF, compared to abstinence.

Overall, the risk of AF rose up eight percent for every increase of 10 grams (third of an ounce) in daily alcohol intake by the study participants. That may sound surprising, Sone said, since moderate drinking is thought to be protective against coronary heart disease, in which plaque builds up in the arteries.

But moderate drinking has never been linked to a decreased risk of AF.

Atrial fibrillation stems from a problem in the heart muscle's electrical activity. Unlike ventricular fibrillation, which affects the heart's lower pumping chamber, AF is not immediately life-threatening. In some cases, an AF episode is short-lived and goes away on its own.

But in others, AF becomes recurrent or permanent, raising their risk of heart failure and of blood clots that can travel to the brain and cause stroke.

More than 2.6 million Americans will suffer AF this year, according to the US Centers for Disease Control and Prevention. It becomes more common with older age and in those with additional risk factors such as high blood pressure, diabetes, obesity and hyperthyroidism.

The findings, however, do not necessarily mean cutting out alcohol altogether is a good way of lower one's risk for AF.

Sone said that moderate drinking is still considered a heart-healthy habit for most people, since coronary heart disease is a much more common cause of death than AF. But, he added, people who have ever had an episode of AF might benefit from not drinking.

Dr. Kenneth J. Mukamal of Harvard University and Beth Israel Deaconess Medical Center in Boston said it was not surprising that moderate drinking appears to offer no protection from AF.

"The ways in which alcohol might prevent coronary heart disease -- like better HDL cholesterol and less clotting -- are irrelevant for risk of AF," said Mukamal in an email to Reuters reporter Amy Norton Amy Norton.

He expressed doubts, though, that moderate drinking would increase the risk of AF.

Two of the studies included in the current analysis, were conducted by Mukamal. He pointed out that of the studies in the current analysis, it was the so-called "case-control" studies that showed the strongest link between drinking and AF. Those kinds of studies -- which compare AF patients with healthy individuals -- are not well-designed for showing cause-and-effect.

A better way to show that is with studies that measure people's drinking habits, then follow them over time to see who develops AF. Based on those types of studies, "there's little risk from chronic drinking in moderation, but heavier drinking -- even rarely -- acutely increases risk," said Mukamal.

The new analysis is reported in the Journal of the American College of Cardiology.


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