Although drinking moderate amounts of alcohol is believed to have cardiovascular benefits, it may also increase the risk of atrial fibrillation, a meta-analysis showed.
In a pooled analysis of 14 observational studies, the highest intake of alcohol was associated with a 51% increased relative risk of atrial fibrillation compared with the lowest intake (OR/RR 1.51, 95% CI 1.31 to 1.74), according to Hirohito Sone, MD, PhD, of the University of Tsukuba Institute of Clinical Medicine in Ibaraki, Japan, and colleagues.
Action Points
- Note that atrial fibrillation is the most common sustained arrhythmia, accounting for 45% of all embolic strokes and is associated with an approximate doubling of all-cause mortality.
- Point out that this meta-analysis suggests that there is a linear relationship between alcohol intake and the risk of sustained atrial fibrillation.
- Also point out that a meta-analysis cannot adjust for all confounders in the included studies and cannot determine causality.
A linear regression analysis indicated that there was a dose-response relationship, with an 8% increased relative risk of atrial fibrillation for every additional 10 grams of alcohol consumed (P<0.001), Sone and co-authors reported in the Jan. 25 issue of the Journal of the American College of Cardiology.
"These regression analyses suggest no evidence that moderate alcohol consumption is beneficial in ameliorating the risk of atrial fibrillation, unlike that of cardiovascular disease," the researchers wrote.
"If anything, moderate alcohol drinkers may have a greater risk of atrial fibrillation than nondrinkers, although the ... risk is not as large as that for heavy drinkers," they added.
Sone and his colleagues identified 14 cohort or case-control studies -- including 130,820 participants and 7,558 cases -- that examined the link between drinking and atrial fibrillation and atrial flutter. Half of the studies were conducted in Europe and half were conducted in North America.
If units of alcohol, rather than grams of alcohol per day, were reported, a unit was considered equal to 12 grams of ethanol.
The cutoff for the highest intake of alcohol was two or more drinks per day for men, one or more drinks per day for women, or 1.5 or more drinks per day for both sexes combined.
Because some studies reported odds ratios and some reported relative risks, the pooled analysis resulted in a combined odds ratio/relative risk, which was increased for the heaviest drinkers compared with the lightest drinkers.
When the analysis was limited to six studies in which nondrinkers were the reference group, the elevated risk was smaller, but still significant (OR/RR 1.36, 95% CI 1.18 to 1.57).
The finding was consistent in nearly all subgroups, although the strength of the relationship varied.
For example, a stronger association was found when the type of study endpoint was paroxysmal atrial fibrillation-dominant (OR/RR 1.92, 95% CI 1.44 to 2.56) or atrial fibrillation recurrence versus a first episode (OR/RR 2.37, 95% CI 1.44 to 3.90), whereas it was weaker when atrial flutter was included (OR/RR 1.25, 95% CI 1.10 to 1.43) than when it was not (OR/RR 1.83, 95% CI 1.45 to 2.30).
Although a causal relationship between heavy alcohol consumption and atrial fibrillation cannot be established, there are some plausible mechanisms connecting the two, according to Sone and his colleagues.
"One speculation is based on biological findings that suggest a harmful effect of high alcohol intake on maintenance of normal heart rhythm, including the achievement of a hyperadrenergic state, impairment of vagal tone, direct effect on myocardial structure, and various electrophysiological changes in atrial cells," they wrote.
Another potential explanation is based on studies suggesting that the development of chronic heart failure accompanied by long-term excessive alcohol consumption may result in an elevated risk of atrial fibrillation.
And finally, the authors wrote, it is possible that atrial fibrillation risk with heavy drinking could be explained by the alcohol-related development of hypertension.
They acknowledged several limitations to their analysis: variation in the definition of heavy drinking across studies, the lack of information in most studies about whether the method for assessing alcohol intake was validated, little information on racial differences among the participants, and the possibility of missing asymptomatic paroxysmal atrial fibrillation.
In addition, no studies looked at the effect of different types of alcoholic drinks, it could not be ruled out that the associations could have varied based on drinking patterns, meta-analyses cannot completely adjust for all potential confounders, and the findings could be biased by the design and methodological features of the included studies.
Disclosures
Sone and one of his co-authors are recipients of a Grant-in-Aid for Scientific Research and Postdoctoral Research Fellowship, respectively, from the Japan Society for the Promotion of Science. The study was also financially supported by the Japan Cardiovascular Research Foundation and Japanese Ministry of Health, Labor, and Welfare.
The authors reported that they had no conflicts of interest.
Primary Source
Journal of the American College of Cardiology
Kodama S, et al "Alcohol consumption and risk of atrial fibrillation: A meta-analysis" J Am Coll Cardiol 2011; 57: 427-436.