Habitual heavy drinking is associated with a 51% increased risk of atrial fibrillation, according to findings from a meta-analysis of more than 130,000 adults, published online Jan. 17.
The impact of occasional heavy alcohol intake on AF, known as "holiday heart syndrome," is well known. The impact of consistent heavy alcohol intake on AF risk, however, has not been well studied, said Dr. Satoru Kodama of the University of Tsukuba Institute of Clinical Medicine in Ibaraki, Japan.
Dr. Kodama and colleagues analyzed data from 14 studies, involving a total of 130,820 participants and 7,558 cases of AF. Across the studies, a common scale of grams per day was used as the standard measure of alcohol intake.
Overall, participants who consumed the most alcohol were significantly more likely to have AF than were those who consumed the least, based on a pooled assessment of odds ratio and relative risk (1.51).
The lowest amount of alcohol consumed in the highest intake category for each of the studies ranged from 1.5 to 6 drinks daily.
Within the highest alcohol intake category, the AF risk was not significantly different between participants who consumed fewer than 4 alcoholic drinks daily, defined as 48 g (OR/RR 1.32), and those who had 4 or more drinks per day (1.74) (J. Am. Coll. Cardiol. 2011;57:427-36).
From an analysis of nine of the studies (involving 126,051 participants and 6,341 cases of AF), the researchers found a significant dose-response relationship between alcohol intake and AF risk, which translated into an increase in relative risk of 1.08 per 10 g of alcohol consumed per day.
Stratified analyses of the data, according to study methods, supported the significant association between the highest category of alcohol intake and AF risk.
The study is the first systematic review of habitual alcohol consumption and AF risk. Although the meta-analysis cannot prove causality, the researchers proposed two hypotheses for a cause and effect relationship. One theory, suggested by biological studies, is that high alcohol intake makes it more difficult for the body to maintain a normal heart rhythm.
"Another speculation is based on reports suggesting that the development of chronic heart failure accompanied by long-term alcohol consumption may result in elevated AF risk," the researchers said.
The results suggest that avoiding alcohol completely, as opposed to drinking moderately, is the best way to reduce AF risk, the researchers concluded.
The analysis was limited by the inability to adjust for various confounders across multiple studies, including the presence of hypertension, diabetes, and obstructive sleep apnea, they wrote. In addition, the strength of the findings is limited by the various definitions of heavy drinking, the lack of information about the validation of alcohol intake, and limited consideration of racial differences among study participants.
Further investigation is needed to determine a possible causal relationship between daily alcohol intake and AF risk, the authors wrote.
The researchers reported having no financial conflicts of interest.