Even Very Low Alcohol Consumption Ups AF Risk

Less than one alcoholic drink a day significantly increases the risk of atrial fibrillation (AF), according to data on more than 100,000 people.

High alcohol consumption—chronic use as well as holiday-related binge drinking—has long been linked to heart arrhythmias, but for lower amounts, there’s only been “inconsistent evidence,” Dora Csengeri, MD (University Heart & Vascular Center Hamburg, Germany), and colleagues say. There are also questions over whether mild-to-moderate drinking might provide cardiovascular benefits that outweigh this risk.

Senior author Renate B. Schnabel, MD (University Heart & Vascular Center Hamburg and German Centre for Cardiovascular Research, Berlin), told TCTMD that thanks to the large data set, her group was able to demonstrate even low alcohol consumption is connected to a rise in AF. This wasn’t entirely surprising, she said. More unexpected was the finding that heart failure wasn’t a driver of the arrhythmias. “There was no interaction,” Schnabel noted.

Jorge A. Wong, MD, MPH, and David Conen, MD, MPH (both Population Health Research Institute, Hamilton, Canada), writing in an editorial, praise the study’s “very large sample size and great power to detect significant relationships between alcohol intake and AF, including the lower spectrum of alcohol consumption where the risk of incident AF is expected to be small.”

The results were published online today in the European Heart Journal.

Risk Begins at Less Than a Drink

Csengeri et al analyzed data from five European cohorts of the MORGAM/BiomarCaRE projects on 100,092 people (median age 47.8 years; 48.3% men) without prior arrhythmias who had baseline examinations between 1982 and 2010. Median alcohol consumption was 3 g per day.

Over a median follow-up of 13.9 years, 5,854 of these individuals developed AF.

The researchers counted 12 grams of alcohol as one drink. Stratified by sex and cohort in a Cox regression analysis, alcohol’s association with incident AF was nonlinear and positive; it became significant when alcohol averaged just one-quarter of a drink daily. With one drink per day, risk was 16% higher than with no consumption. There were no differences across alcohol types.

Risk of Incident AF

For a subset of 23,205 participants, the researchers measured N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high-sensitivity troponin I from stored blood samples. “Circulating cardiac biomarkers are quantitative measures which shed light on current cardiac pathophysiology,” they note. “Troponin reflects myocardial injury, while [NT-proBNP] indicates often chronic, subclinical wall stress.”

Additionally, the investigators looked at patterns in heart failure, also predicted by alcohol consumption and itself a risk factor for atrial fibrillation.

Yet alcohol’s impact on AF was “neither fully explained by cardiac biomarker concentrations nor by the occurrence of heart failure,” the researchers note.

Net Clinical Benefit Unknown

Wong and Conen, in their editorial, say the study provides “solid evidence that even very low levels of alcohol” have a connection to AF. They also point to some limitations, however. AF episodes weren’t adjudicated and were only captured if they led to hospitalization or were mentioned on death certificates. Moreover, binge drinking wasn’t accounted for, nor was the study designed to tease out mechanism.

To TCTMD, Schnabel said that mechanisms aren’t clear. “This is where we can only speculate. It must have to do something with chronic changes,” she observed. As noted in their paper, habitual drinking can alter cardiac structure and function, resulting in cardiomyopathy and atrial remodeling, but long-term consumption of small alcohol amounts hasn’t been fully studied. Acute consumption, on the other hand, “induces autonomic imbalance reflected by sinus tachycardia, predisposing to arrhythmia,” the researchers explain. “Electrolyte disturbance and alterations of the acid-base balance are further proarrhythmic triggers.”

Wong and Conen mention another missing puzzle piece: the absolute risk of AF on the lower end of the alcohol spectrum. “This important issue has to be taken into account when also considering the potentially beneficial associations of modest alcohol intake with other cardiovascular outcomes,” they stress, adding that “any reduction in low-to-moderate alcohol consumption to potentially prevent AF needs to be balanced with the potentially beneficial association low amounts alcohol may have with respect to other cardiovascular outcomes.”

The editorialists suggest further study into the net clinical benefit of alcohol at this level, a goal that Schnabel also finds worthwhile. “Until then,” Wong and Conen conclude, “each individual has to make [his or her] own best educated decision as to whether consuming up to one alcoholic drink per day is worthwhile and safe.”

Schnabel, asked about the absolute risk difference, said she encounters this question a lot.

“It’s not easy to calculate. It can be done with complex modeling, but the results of these complex models then again are not [easily] interpretable,” Schnabel explained. Survival models, like the ones used here to calculate incident HF, take into account passing time, so it’s hard to capture this as a single number.

What can be said, she continued, is that the absolute differences in AF risk posed by low alcohol consumption “certainly are very small.”

Clinicians counseling patients, then, need to interpret these results carefully, Schnabel said.

Data have shown that regular but low-to-moderate alcohol consumption can be protective against MI, she observed, and up to 100 grams per week of alcohol doesn’t appear to raise the risk of mortality. “On the other hand, I would say for that patients at risk of atrial fibrillation, we should clearly discuss it with them and remind them to reduce their alcohol consumption. Certainly, do not binge drink,” Schnabel advised, adding that for patients with preexisting AF who are regular drinkers, abstinence may reduce recurrence.