Critiques from the ISFAR look at research into the health effects of consuming alcohol

Critiques from the ISFAR look at research into the health effects of consuming alcohol

A recent study in Denmark tested the hypothesis that alcohol consumption, both observational (self-reported) and estimated by genetic instruments, is associated with the risk of atrial fibrillation (AF) and to determine whether people with high cardiovascular risk are more sensitive towards alcohol than people with low risk.

(Atrial fibrillation is a heart condition that causes an irregular and often abnormally fast heart rate.)

The research was based on a large cohort of subjects (more than 88,000) with a mean follow-up period of 6.1 years; there were almost 3,500 cases of AF diagnosed from hospital records during follow up. Unfortunately, the authors did not have data to identify binge drinkers, which tend to show greater adverse cardiovascular events than regular moderate drinkers whose weekly intake may be the same.

The main results of the study were that men consuming more than 14 drinks per week, especially those consuming more than 28 drinks per week, had an increase in risk of AF, but no significant increase in risk was seen for any level of alcohol intake among women. When genotypes affecting alcohol metabolism (AHD1B, ADH1C) were studied in a Mendelian randomisation analysis, the authors state that they "found no evidence to support causality of the observational findings".

ISFAR reviewers of this research considered it to be a well-done study with appropriate analyses. Its results reflect the findings of most previous prospective studies and meta-analyses of little effect of light drinking on AF, but an increase in risk for heavier drinkers. The study also showed that the effects of alcohol consumption on the risk of AF were not different between subjects who had cardiovascular disease or were at high-risk of cardiovascular disease than for other subjects. 

While Mendelian randomization using genetic factors affecting alcohol metabolism has been touted as an unbiased approach for judging causal health effects of alcohol, there are questions about the adequacy of such instruments for judging effects. In this study, their use did not suggest that the relations shown by the self-report of alcohol by subjects necessarily indicated a causal association of alcohol with AF.

Overall, current data suggests that heavy drinking, and in particular binge drinking, is associated with an increased risk of atrial fibrillation, especially among men, but there is little evidence of a meaningful increase in risk if drinking within low risk guidelines. Fortunately, such levels of alcohol intake (some guidelines suggest no more than two drinks per day for men or one drink per day for women) have been shown from many previous studies to significantly lower the risk of cardiovascular disease and total mortality.

To read the full critique, click here.

These critiques are published with the permission of The ISFAR.