According to the National Institute on Alcohol Abuse and Alcoholism (NIAAA), around 71 percent of Americans report consuming alcohol in the past year, while almost 57 percent report drinking in the past month.
While heavy drinking is known to be severely detrimental to health, accounting for around 3.3 million deaths in the United States in 2012, an array of studies have suggested moderate alcohol intake may be beneficial for heart health.
Earlier this year, for example, a study reported by Medical News Today associated consuming three to five drinks a week with lower risk of heart attack and heart failure.
However, in the new study, senior author Dr. Gregory Marcus – of the University of California-San Francisco (UCSF) – and colleagues suggest moderate alcohol intake may not be so good for the heart after all.
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The researchers publish their findings in the Journal of the American Heart Association.
The team analyzed the data of 5,220 participants of an average age of 56 who were part of the Framingham Heart Study.
Electrocardiograms (ECG) were used to assess the electrical activity of the participants’ hearts, enabling identification of atrial fibrillation (AF) – a condition characterized by irregular heartbeat.
Information on subjects’ alcohol intake was gathered from standard medical questionnaires.
AF risk increased with every 10 grams of alcohol consumed daily
Over 6 years of follow-up and more than 17,600 ECG scans, the researchers identified 1,088 cases of AF, and long-term alcohol intake was found to raise the risk for this condition.
Results of the analysis revealed that the more alcohol participants consumed, the greater their risk of AF; each 10 grams of alcohol consumed each day (just under one drink daily) was linked to a 5 percent greater risk of new-onset AF.
The researchers say this increased risk of AF is likely down to enlargement of the heart’s left atrium as a result of alcohol intake; each additional 10 grams of alcohol consumed daily was associated with a 0.16 millimeter increase in size of the left atrium.
What is more, around 24 percent – and up to 75 percent in some cases – of the relationship between regular alcohol intake and risk of AF could be explained by enlargement of the heart’s left atrium, the team reports.
These findings remained after accounting for a wealth of possible confounding factors, such as blood pressure, smoking status, and diabetes.
“Our study provides the first human evidence of why daily, long-term alcohol consumption may lead to the development of this very common heart rhythm disturbance.
We were somewhat surprised that a relatively small amount of alcohol was associated with a larger left atrium and subsequent atrial fibrillation.”
Dr. Gregory Marcus
The researchers are unable to conclude that alcohol intake is a direct cause of AF, but they say the results challenge previous studies linking moderate alcohol consumption to better heart health.
“Our data suggest atrial fibrillation might be prevented by avoiding alcohol – however, just as alcohol likely has variable effects on individuals, there are almost certainly various mechanistic subtypes of atrial fibrillation,” says Dr. Marcus. “It’s not one size fits all when it comes to the effects of alcohol and heart health.”
The team concludes that further studies are needed to better understand the underlying mechanisms by which alcohol intake influences the electrical activity of the heart.
“Our hope is that by understanding the mechanistic relationship between alcohol and atrial fibrillation we might learn something inherent to atrial fibrillation in general that could help identify new ways of understanding and treating the disease,” says Dr. Marcus.
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