First to show a hint of protection
The current study “is especially noteworthy because it’s the really the first to demonstrate any hint that there could be a protective effect from any particular amount of alcohol in regard to atrial fibrillation,” Gregory M. Marcus, MD, MAS, University of California, San Francisco, said in an interview. “The J-shaped association fits with what’s been observed with myocardial infarction and overall mortality, and hasn’t previously been seen in the setting of atrial fibrillation.”
Quite interestingly, “it appeared to be the wine drinkers, rather than those who consumed other types of alcohol, that enjoyed this benefit,” said Dr. Marcus, who was not involved in the research but co-authored an accompanying editorial with UCSF colleague Thomas A. Dewland, MD.
“It’s important to recognize the overwhelming evidence that alcohol in general increases the risk for atrial fibrillation,” he said. But “perhaps there’s something in wine that is anti-inflammatory that has some beneficial effect that maybe overwhelms the proarrhythmic aspect.”
The current study “opens the door to the question as to whether there is a small amount of alcohol, perhaps in the form of wine, where there are some benefits that outweigh the risks of atrial fibrillation.”
Still, the findings are observational and “clearly prone to confounding,” Dr. Marcus said. “We need to be very cautious in inferring causality.”
For example, it’s possible that “there is something about individuals that are able to drink alcohol on a regular basis and in small amounts that is the actual causal factor in reducing atrial fibrillation episodes.”
The analysis was based on 403,281 participants in the UK Biobank registry, a prospective cohort study in the United Kingdom, who were aged 40-69 when recruited from 2006 to 2010; it excluded anyone with a history of AFib or who was a former drinker. About 52% were women, the report noted.
Their median alcohol consumption was eight U.K. drinks per week, with 5.5% reporting they had never consumed alcohol. About 21,300 incident cases of AFib or atrial flutter were documented over almost 4.5 million person-years, or a median follow-up of 11.4 years.
The hazard ratio for incident AFib among those with a weekly alcohol consumption corresponding to 1-7 U.K. drinks, compared with intake of less than 1 U.K. drink per week, was 0.95 (95% confidence interval, 0.91-1.00). Within that range of 1-7 drinks, the absolute lowest AFib risk on the J curve was at 5 per week.
No increased risk of new AFib was seen in association with weekly U.K. drink levels of 10 for red wine, 8 for white wine, and 3 for spirits.
Compared with weekly intake of less than 1 U.K. drink per week, red wine intake at 1-7 per week showed an HR for AFib of 0.94 (95% CI, 0.91-0.97). Indeed, at no observed consumption level was red wine associated with a significant increase in AFib risk. White wine until the highest observed level of intake, above 28 U.K. drinks per week, at which point the HR for AFib was 1.48 (98% CI 1.19-1.86). The curve for spirit intake followed a similar but steeper curve, its HR risk reaching 1.61 (95% CI, 1.34-1.93) at intake levels beyond 28 U.K. drinks per week.
Consumption of beer or cider showed a linear association with AFib risk, which was elevated at all recorded intake levels, including 8-14 U.K. drinks per week (HR, 1.11; 95% CI 1.06-1.17) and up to 28 or more per week (HR, 1.35; 95% CI, 1.26-1.45).
The analysis is hypothesis generating at best, Dr. Marcus emphasized. “Ultimately, a randomized trial would be the only way to be fairly certain if there is indeed a causal protective relationship between red wine, in low amounts, and atrial fib.”
The message for patients, proposed Dr. Dewland and Dr. Marcus, is that alcohol abstinence is best for secondary AFib prevention, “especially if alcohol is a personal trigger for acute AF[ib] episodes,” and that for primary AFib prevention, “continued consumption of some alcohol may be reasonable, but the exact threshold is unclear and is likely a very low amount.”
Mr. Tu has disclosed no relevant financial relationships. Disclosures for the other authors are in the report. Dr. Marcus disclosed receiving research funding from Baylis Medical; consulting for Johnson & Johnson and InCarda; and holding equity interest in InCarda. Dr. Dewland reports no relevant financial relationships.
A version of this article first appeared on Medscape.com.