Moderate alcohol consumption may increase risk of atrial fibrillation

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Yan Liang, Cardiovascular Institute and Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, and others reported in the Canadian Medical Association Journal that moderate alcohol consumption may increase the risk of atrial fibrillation among people with existing cardiovascular disease and that binge drinking further increases this risk.

Liang et al commented that heavy alcohol consumption and binge drinking are associated with an increased risk of incident atrial fibrillation in the general population, but added that the association between moderate alcohol consumption and incident atrial fibrillation in older patients with existing cardiovascular disease is not clear. They wrote: “We examined whether drinking moderate quantities of alcohol, and binge drinking, would be associated with an increased risk of incident atrial fibrillation in a large cohort of patients with existing cardiovascular disease or diabetes with end-organ damage.”

Using data from the ONTARGET (Ongoing telmisartan alone and in combination with ramipril global endpoint trial) and TRANSCEND (Telmisartan randomised study in ACE intolerant subjects with cardiovascular disease) trials, Liang et al analysed data for 30,433 patients. They categorised patients into groups according to the level of alcohol consumption: low intake (2 drinks per day for women and >3 drinks per day for men). The authors also assessed binge drinking among the study population, which was defined as having more than five drinks at any one time or an average ingestion of more than five drinks per day. Binge drinkers could be either moderate drinkers or high-intake drinkers. Liang et al then assessed the rate of incident atrial fibrillation in the different groups.

According to the authors, there was a graded increase in the incidence of atrial fibrillation with alcohol consumption. They reported: “Our findings suggest that the effect of increased alcohol consumption, even in moderate amounts, on the risk of atrial fibrillation among patients with existing cardiovascular disease may be considerable. Using Levin’s formula for calculating attributable risk, we estimate that for every 100 events of atrial fibrillation occurring in the population of moderate drinkers, an estimated 4.9 events would be prevented if every person quit drinking.”

Furthermore, Liang et al found that binge drinking was also associated with atrial fibrillation. They wrote: “Bringe drinking, even by those in the moderate-intake group, was significantly associated with an increased incidence of atrial fibrillation, with the magnitude of risk comparable to habitual heavy drinking.” However, binge drinking was not solely responsible for the increased risk of atrial fibrillation observed in the moderate- and high-intake groups. The authors commented that after binge drinkers were excluded from the analysis, the risk of atrial fibrillation among both moderate- and high-intake drinkers “remained robust”.

Speculating as to why moderate alcohol consumption appeared to have a negative impact in a population of patients with cardiovascular disease when moderate consumption is associated with a reduced risk of all-cause death and cardiovascular disease in a healthy population, Liang et al suggested that drinking moderate amounts of alcohol may have enabled the patients in the study to survive long enough to develop atrial fibrillation but added further analysis indicated that the “harmful effect of alcohol on atrial fibrillation persisted despite the potential for competing risks from death.” They also said that studies have shown that alcohol consumption has “harmful effects on maintenance of normal heart rhythm, including a hyperadrenergic state and impairment of vagal tone” and that the reasons behind the association between alcohol consumption and atrial fibrillation were “likely multifactorial”.

They concluded: “Recommendations about the protective effects of alcohol intake in patients at high risk of cardiovascular disease may need to be tempered with these findings.”

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