Women who have up to two alcoholic drinks per day do not appear to be at increased risk of atrial fibrillation (irregular heart beat), but drinking more than that amount is associated with a higher risk, according to a study in the December 3 issue of JAMA.

Studies assessing the effects of regular alcohol consumption on the risk of atrial fibrillation have provided inconsistent results, with several studies finding significant associations between moderate to high amounts of alcohol intake and increased risks of atrial fibrillation among men, but not among women. However, these studies were not of adequate size to detect significant associations among women, according to background information in the article.

David Conen, M.D., M.P.H., of Brigham and Women’s Hospital, Harvard Medical School, Boston, and University Hospital, Basel, Switzerland, and colleagues analyzed data from a completed randomized controlled trial involving 34,715 women participating in the Women’s Health Study, to assess the effects of regular alcohol consumption on the risk of atrial fibrillation. The participants were older than 45 years and had no atrial fibrillation at the start of the study and underwent follow-up from 1993 to October 2006. Alcohol consumption was assessed via questionnaires at the beginning of the trial and at 48 months of follow-up and was grouped into 4 categories: 0 drinks per day, greater than 0 and less than 1, 1 or more and less than 2, and 2 or more drinks per day. Atrial fibrillation was self-reported on the yearly questionnaires and subsequently confirmed by electrocardiogram and medical record review.

During a median (midpoint) follow-up of 12.4 years, there were 653 confirmed cases of new atrial fibrillation. Among women consuming no alcohol (n = 15,370), there were 294 events (1.9 percent); for women consuming more than 0 and less than 1 drink per day (n = 15,758), there were 284 events (1.8 percent); for 1 to 2 drinks per day (n = 2,228), there were 35 events (1.6 percent); and for women consuming 2 or more drinks per day (n = 1,359), there were 40 atrial fibrillation events (2.9 percent).

“In the present study, alcohol consumption of up to 2 drinks per day was not associated with an increased risk of incident atrial fibrillation among initially healthy, middle-aged women. In contrast, the small group of women who consumed 2 or more alcoholic beverages per day had a 1.6-fold greater risk for atrial fibrillation relative to nondrinking women. 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,” the authors write.

(JAMA. 2008;300[21]:2489-2496. Available pre-embargo to the media at jamamedia.org)

Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Source: American Medical Association (AMA)