Alcoholic drinks are in the news again, served with a twist. A large cohort study saw a familiar J-shaped curve detailing risk for new atrial fibrillation (AF) in which the risk rose steadily with greater number of drinks per week, except at the lowest levels of alcohol intake.
There, the curve turned the other way. Light drinkers overall showed no higher AF risk than nondrinkers, and the risk was lowest at any degree of alcohol intake up to 56 g per week.
On closer analysis of risk patterns, the type of alcoholic beverage mattered. Modest weekly intake of red wine, at least one serving but no more than seven, may have actually protected against new AF compared with zero intake.
Alcohol content per drink was defined by standards in the United Kingdom, where the cohort was based.
The risk of AF also didn’t climb at low intake levels of white wine or with “very low” use of liquor or spirits. But it went up consistently at any level of beer or cider consumption, and to be sure, “high intake of any beverage was associated with greater AF risk,” notes a report on the study published July 27 in JACC: Clinical Electrophysiology.
The results, based on more than 400,000 adults in the community, “raise the possibility that, for current consumers, drinking red or white wine could potentially be a safer alternative to other types of alcoholic beverages with respect to AF risk,” the report proposes.
The J-shaped risk curve for new AF by degree of alcohol consumption follows the pattern sometimes seen for cardiovascular risk in general. But the intake level at which AF risk is flat or reduced “is at a far lower dose of alcohol than what we’ve seen for cardiovascular disease,” lead author Samuel J. Tu, BHlthMedSc, told theheart.org | Medscape Cardiology.
“That being said, even with the threshold sitting quite low, it still tells us that cutting down on alcohol is a good thing and perhaps one of the best things for our heart,” said Tu, University of Adelaide and Royal Adelaide Hospital, Australia, who also presented the findings at the Heart Rhythm Society (HRS) 2021 Scientific Sessions, held in Boston, Massachusetts and virtually.
How Much Alcohol is in a Drink?
In a caution for anyone looking to beer, wine, or liquor to protect against AF, or at least not cause it, the weekly number of drinks associated with the lowest AF risk may be fewer than expected. That bottom of 56 g per week works out to one drink a day or less for Brits and only 4 or fewer per week for Yanks, according to the study’s internationally varying definitions for the alcohol content of one drink.
For example, a drink was considered to have 8 g of alcohol in the UK, 14 g in the United States and some other countries, and up to 20 g in Austria. Those numbers came from definitions used by the respective national health agencies, such as the National Health Service in the UK and Centers for Disease Control and Prevention in the US, Tu explained.
“They all defined standard drinks slightly differently. But wherever we looked, the threshold we found was far lower than what our governments recommend” based on what is known about alcohol and overall cardiovascular risk, he said.
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, told theheart.org | Medscape Cardiology.
“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 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,” 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 to 69 when recruited from 2006 to 2010; it excluded anyone with a history of AF or who was a former drinker. About 52% were women, the report notes.
Their median alcohol consumption was 8 UK drinks per week, with 5.5% reporting they had never consumed alcohol. About 21,300 incident cases of AF or atrial flutter were documented over almost 4.5 million person-years, or a median follow-up of 11.4 years.
The hazard ratio (HR) for incident AF among those with a weekly alcohol consumption corresponding to 1 to 7 UK drinks, compared with intake of less than 1 UK drink per week, was 0.95 (95% CI, 0.91 – 1.00). Within that range of 1 to 7 drinks, the absolute lowest AF risk on the J curve was at 5 per week.
Risks by Type of Drink
No increased risk of new AF was seen in association with weekly UK drink levels of 10 for red wine, 8 for white wine, and 3 for spirits.
Compared with weekly intake of less than 1 UK drink per week, red wine intake at 1 to 7 per week showed an HR for AF of 0.94 (95% CI, 0.91 – 0.97). Indeed, at no observed consumption level was red wine associated with a significant increase in AF risk.
There was no such risk increase with white wine until the highest observed level of intake, above 28 UK drinks per week, at which point the HR for AF 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 UK drinks per week.
Consumption of beer or cider showed a linear association with AF risk, which was elevated at all recorded intake levels, including 8 to 14 UK 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, 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, propose Dewland and Marcus, is that alcohol abstinence is best for secondary AF prevention, “especially if alcohol is a personal trigger for acute AF episodes,” and that for primary AF prevention, “continued consumption of some alcohol may be reasonable, but the exact threshold is unclear and is likely a very low amount.”
Tu has disclosed no relevant financial relationships. Disclosures for the other authors are in the report. Marcus discloses receiving research funding from Baylis Medical; consulting for Johnson & Johnson and InCarda; and holding equity interest in InCarda. Dewland reports no relevant financial relationships.
JACC: Clinical Electrophysiology. Published online July 27, 2021. Report, Editorial
Heart Rhythm Society 2021 Scientific Sessions: Poster 02-004. Presented July 29, 2021.
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