Heavy drinkers were 32% more likely to develop AF over five years than light drinkers, according to a study in Canada.
Researchers from McMaster University in Ontario, Canada, said the findings showed alcohol intake is a 'considerable' risk factor for AF among these patients.
Alcohol may have a mild protective effect against heart disease in healthy people. But little is known about its effects on patients at risk of cardiovascular events.
In the study, researchers assessed data from 30,433 participants aged over 55 without AF, who were enrolled in two large antihypertensive drug trials. All patients had a history of cardiovascular disease or diabetes with end-organ damage.
Researchers assessed self-reported drinking levels and linked this to incidence of AF after almost five years.
They defined low levels in women as one drink per day, moderate as up to two drinks per day, and high as more than two drinks per day. In men, thresholds for moderate and high drinking levels were up to three and more than three drinks per day respectively. Binge drinking was defined as more than five drinks per day.
Researchers found 2,093 patients had developed AF over this time, with 14.5 cases per 1,000 person-years among light drinkers. This rose to 17.3 among moderate drinkers and 20.8 among heavy drinkers.
This meant that moderate drinkers were 14% more likely to develop AF and heavy drinkers 32% more likely compared with light drinkers. The risk of binge drinking was similar to that of regular heavy drinking.
Researchers believe alcohol may interfere with heart rhythm signals, but that many other processes are likely to be involved.
Researchers concluded: 'Because drinking moderate quantities of alcohol was common in our study, our findings suggest that the effect of increased alcohol consumption, even in moderate amounts, on the risk of AF among patients with existing cardiovascular disease may be considerable.'
They warned that advice about the protective benefits of drinking alcohol 'may need to be tempered with these findings'.