Healthy middle-age women can have up to two alcoholic drinks a day without apparently being at risk of irregular heartbeat, according to a study out Tuesday.
But having more than two alcoholic drinks is associated with an increased risk of irregular heartbeat, also known as atrial fibrillation, read the report in the December 3 issue of Journal of the American Medical Association (JAMA).
Several studies established strong links between medium to heavy drinking and higher risk of atrial fibrillation among men, but not among women, mainly because not enough women were included in previous studies for credible results, the authors said.
The current study is based on 34,715 women aged 45 and older and in good health at the start of the trial.
"In the present study, alcohol consumption of up to two drinks per day was not associated with an increased risk of incident atrial fibrillation among initially healthy, middle-aged women," wrote David Conen of Brigham and Women's Hospital and Harvard Medical School, one of the study co-authors.
"In contrast, the small group of women who consumed two or more alcoholic beverages per day had a 1.6-fold greater risk for atrial fibrillation relative to nondrinking women," he wrote.
Alcohol consumption was assessed via questionnaires at the beginning of the trial and at follow-up checks.
Irregular heartbeat was self-reported on annual questionnaires and later confirmed through a medical checkup.
"While this finding needs to be interpreted with some caution because of the small number of women in some subgroups, it supports a possible threshold effect in the relationship between alcohol consumption and risk of atrial fibrillation among women," Conen wrote.