Even moderate alcohol consumption may change the structure of the heart in ways that increase the risk of atrial fibrillation (AF), found a University of California – San Francisco study.
“There’s growing evidence that moderate alcohol intake may be a risk factor for atrial fibrillation, the most common heart rhythm disturbance in the world, but the mechanism by which alcohol may lead to atrial fibrillation is unknown,” said Dr Gregory Marcus, endowed professor of atrial fibrillation research at UCSF and senior author of the study.
Marcus and colleagues looked at damage to the left atrium of the heart as a possible pathway between alcohol and atrial fibrillation. Atrial fibrillation is a known risk factor for stroke. The irregular pumping of blood can lead to blood clots, which may travel to the brain and cause stroke.
The researchers evaluated data from more than 5,000 adults collected over several years in the Framingham Heart Study, including echocardiograms, medical history and self-reported alcohol intake. The study participants, mostly white and in their 40s to 60s, reported on average just over one drink per day. The overall rate of atrial fibrillation in the group was 8.4 cases per 1,000 people per year – meaning over a 10-year period, eight out of 100 people were likely to develop atrial fibrillation.
Every additional drink per day was associated with a 5% increase in the yearly risk. Every additional drink per day also was associated with a statistically significant 0.16 millimeter enlargement of the left atrium, highlighting a possible site of physical damage caused by drinking.
The new findings shed light on the complex relationship between alcohol and heart health – one that likely precludes blanket advice on drinking habits, said Marcus.
Research has shown that moderate drinking can reduce the risk of heart attack while increasing the risk of atrial fibrillation. Marcus’s team captured this conundrum in a study published earlier this year looking at hospital admissions in dry and wet counties of Texas. They found that patients in counties permitting alcohol sales were more likely to have atrial fibrillation but less likely to have heart attacks and congestive heart failure.
Alcohol’s abilities to protect and harm the heart likely operate through different mechanisms and vary from person to person, said Marcus. The work in his group seeks to decipher these mechanisms, which will inform therapies for heart conditions and may ultimately enable physicians to give personalised advice to patients.
“I’m constantly trying to remind people that there are various forms of heart disease and not all are related to heart attack,” said Marcus, who is also a practicing cardiologist. “Atrial fibrillation is growing in importance as our success in preventing heart attack grows.” He added that one pattern, revealed by UCSF’s Health eHeart Study, is clear – people who believe alcohol is good for the heart tend to drink more.
Background: Alcohol consumption has been associated with atrial fibrillation (AF) in several epidemiologic studies, but the underlying mechanisms remain unknown. We sought to test the hypothesis that an atrial myopathy, manifested by echocardiographic left atrial enlargement, explains the association between chronic alcohol use and AF.
Methods and Results: We evaluated the relationship between cumulative alcohol consumption and risk of incident AF in 5220 Offspring and Original Framingham Heart Study participants (mean age 56.3 years, 54% women) with echocardiographic left atrial size measurements. The incidence of AF was 8.4 per 1000 person‐years, with 1088 incident AF cases occurring over a median 6.0 years (25th–75th percentiles 4.0–8.7 years) of follow‐up. After multivariable adjustment for potential confounders, every additional 10 g of alcohol per day (just under 1 drink per day) was associated with a 0.16 mm (95% CI, 0.10–0.21 mm) larger left atrial dimension. Also in multivariable adjusted analysis, every 10 g per day of alcohol consumed was associated with a 5% higher risk of developing new‐onset AF (hazard ratio, 1.05; 95% CI, 1.01–1.09). An estimated 24% (95% CI, 8–75) of the association between alcohol and AF risk was explained by left atrial enlargement.
Conclusions: Our study of a large, community‐based sample identified alcohol consumption as a predictor of left atrial enlargement and subsequent incident AF. Left atrial enlargement may be an intermediate phenotype along the causal pathway linking long‐term alcohol consumption to AF.
David D McManus, Xiaoyan Yin, Rachel Gladstone, Eric Vittinghoff, Ramachandran S Vasan, Martin G Larson, Emelia J Benjamin, Gregory M Marcus