Drinking alcohol, even in moderate amounts, may increase the size of the heart's left atrium, a new study finds. The left atrium is one of the two upper chambers of the heart, along with the right atrium.
Moderate consumption of alcohol was regarded as healthy for based on studies of coronary disease risk, but new findings suggest otherwise.
Results of a new observational study show that middle-aged and older adults who drink as little as one drink per day on average are left with a risk of developing a type of irregular heartbeat called atrial fibrillation (A-fib), which can lead to other problems, including stroke.
"Despite the widely held belief by the public that alcohol has a beneficial effect on general heart health, acute alcohol consumption has long been linked to the development of [atrial fibrillation]", said Dr. David McManus.
Senior author Gregory Marcus, MD (University of California, San Francisco), said the fact that those relationships were seen even at consumption levels of only roughly one drink per day was a little bit surprising and suggests "the even the amounts of alcohol that are considered acceptable by the American Heart Association (AHA), for example, could be harmful to those prone to atrial fibrillation."
The AHA recommends that for those who choose to drink alcohol, it should be done in moderation, defined as one to two drinks per day for men and one drink for women.
Alcohol should not necessarily be considered heart healthy, Marcus said, noting that any protective effect likely involves coronary disease, with unknown effects on other types of disease.
A relationship between alcohol consumption and A-fib has been observed in multiple studies, but the main unknown has been the mechanism. Heavy alcohol use has been shown to impair ventricular function, and it is possible that the atria—which seem to be more prone to damage than the ventricles—could be enlarged with even small-to-moderate amounts of alcohol.
To test whether that occurs and whether it could represent a possible mechanism to explain the link between drinking alcohol and A-fib, the investigators looked at data from 5,220 participants who were enrolled in the Framingham Heart Study or the children of those who participated in the study. They underwent echocardiographic measurements of left atrial size. Most were free from cardiovascular disease at baseline.
At the beginning of the study, the average age of participants was 56 years and their mean left atrial dimension was 38.3. mm. Average alcohol consumption was 13.3 grams per day. Through a median follow-up of 6 years, the incidence of A-fib was 8.4 per 1,000 person-years.
Over the study period, the researchers found that every additional 10 grams of alcohol (just less than one drink) consumed daily was linked to a 0.16-millimeter (0.006 inches) increase in the diameter of the left atrium.
Although incrementally greater amounts of alcohol consumption were associated with larger left atrial sizes, there was no relationship between intake and the change in left atrial dimension over time.
After adjustment for left atrial dimension, the link between alcohol intake and A-fib became nonsignificant. The authors estimated that 24% of the association could be explained between alcohol and left atrial enlargement.
"These data, although observational, are consistent with the notion that chronic alcohol consumption, even at moderate levels, can be cardiotoxic and lead to pathological atrial structural change that can, in turn, enhance vulnerability to [A-fib] later in life," the authors write.
Further research is needed to identify genetic or environmental exposures that can identify at-risk patients.
"If you're completely healthy in every other way, have no hypertension, exercise, your cholesterol's perfect, and you don't smoke, is it alright to have moderate use of alcohol? Probably," said Mariell Jessup, MD (Hospital of the University of Pennsylvania, Philadelphia), stressing that nobody should be drinking excess. "But if you're drinking more than moderately every day and you have other risk factors including hypertension or older age, I think alcohol may contribute to the development of atrial fibrillation. And the reason, of course, that that's so important is that atrial fibrillation leads to stroke."