People who drink regularly, especially heavy drinkers, may be more likely than teetotalers to suffer atrial fibrillation, a type of abnormal heart rhythm, according to a research review.
In an analysis of 14 studies, a team led by Satoru Kodama at the University of Tsukuba Institute of Clinical Medicine in Japan found that the heaviest drinkers were more likely to be diagnosed with the condition than people who drank little to no alcohol.
Though definitions of "heavy" drinking varied, it meant at least two or more drinks per day for men, and one or more per day for women. In some studies, heavy drinkers downed at least six drinks per day.
While doctors have long known that a drinking binge can trigger an episode of atrial fibrillation (AF), the findings — reported in the Journal of the American College of Cardiology — suggest that usual drinking habits may also matter.
"What we revealed in the current (study) is that not only episodic but habitual heavy drinking is associated with higher risk of AF," said Hirohito Sone, a colleague of Kodama's, told Reuters Health by email.
Atrial fibrillation is the most common abnormal heart rhythm and is not in itself life-threatening, but patients with it are at significantly higher risk of strokes. It may also result in palpitations, fainting, chest pain or congestive heart failure.
When all the study results were combined, heavy drinkers were 51 percent more likely to suffer atrial fibrillation than either non-drinkers or occasional drinkers.
Overall, the risk edged up 8 percent for every increase of 10 grams in participants' daily alcohol intake.
More than 2.6 million U.S. citizens will suffer from atrial fibrillation this year, according to the U.S. Centers for Disease Control and Prevention. The condition becomes more common with age and additional risk factors include high blood pressure, diabetes and obesity.
Since coronary heart disease is much more common cause of death than atrial fibrillation, Sone said moderate drinking — up to one or two drinks per day — is probably still a heart-healthy habit for most people.
A better way to show a connection is with studies that measure people's drinking habits, then follow them over time to see who develops atrial fibrillation, said Kenneth Mukamal of Harvard University and Beth Israel Deaconess Medical Center in Boston, who led two of the studies included in the analysis.
One of Mukamal's studies found a connection only between heavy drinking, with men who had five or more drinks a day having a higher risk of developing the condition over time than occasional drinkers.
Mukamal said that, based on longer-term studies, "there's little risk from chronic drinking in moderation, but heavier drinking — even rarely — acutely increases risk."