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Despite the purported cardiovascular benefits of light drinking, small amounts of alcohol were still linked with incident atrial fibrillation (Afib) in a large observational study.

Increased Afib risk was observed with just one daily drink containing 12 g ethanol (HR 1.16, 95% CI 1.11-1.22), whether the beverage was 120 mL of wine (four-fifths of one standard glass), 330 mL of beer (nearly a can's worth), or 40 mL of spirits (roughly one shot), reported Renate Schnabel, MD, of University Heart & Vascular Center Hamburg, Germany, and colleagues.

Even very low alcohol consumption, at 2 g per day, was marginally associated with Afib risk over nearly 14 years of follow-up (HR 1.02, 95% CI 1.0-1.04), they wrote in the .

Findings were consistent for men and women alike. The relationship between alcohol and new-onset Afib remained after adjustment for heart failure history and the cardiac biomarkers NT-proBNP and hs-troponin I.

"Our large community-based study clearly shows that low alcohol consumption is already associated with increased risk of incident Afib. We observed a non-linearly increasing relationship between alcohol consumption and incident Afib, independent of common confounders," Schnabel's group concluded.

Information on had been lacking in the literature linking chronic drinking and Afib.

"Together with a recent randomized trial showing that a reduction in alcohol intake led to a reduction in Afib recurrence, these data suggest that lowering alcohol consumption may be important for both prevention and management of Afib," commented Jorge Wong, MD, MPH, and David Conen, MD, MPH, both of McMaster University's Population Health Research Institute in Hamilton, Ontario.

"The net clinical benefit of consuming low amounts of alcohol requires further study, ideally in adequately powered randomized trials. Until then, each individual has to make [his or her] own best educated decision as to whether consuming up to 1 alcoholic drink per day is worthwhile and safe," they wrote in an .

For their study, Schnabel and colleagues pooled five community cohorts from Europe totaling 107,845 adults -- then whittled down to 100,092 (median age 47.8; 48.3% men) after excluding people with existing history of Afib or atrial flutter.

Self-reported alcohol consumption was a median 3 g (a quarter of a drink) per day.

Based on questionnaires and hospital records, 5,854 individuals developed Afib over a median 13.9 years.

A J-shaped relationship between drinking and incident heart failure was found as well: consumption of less than 20 g alcohol (1.6 drinks) per day was associated with reduced risk, whereas greater consumption was associated with increased risk, study authors found.

The study's reliance on self-reported drinking patterns was a major limitation, Schnabel's group acknowledged. The researchers also cautioned that they only had biomarker levels at baseline, and that some cases of Afib may have gone undetected given the lack of systematic screening among study participants.

Furthermore, "the study did not report the absolute risks of Afib associated with low levels of alcohol consumption. This important issue has to be taken into account when also considering the potentially beneficial associations of modest alcohol intake with other cardiovascular outcomes," according to Wong and Conen.

"The effects of alcohol on atrial electrophysiology likely depend on multiple factors including changes in atrial repolarization, vagal tone, and direct myocardial injury and fibrosis. More studies examining how alcohol affects atrial electrophysiology via these potential pathways are needed," the editorialists said.

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