Increased Alcohol Consumption Associated with Increased Risk of AFib

An analysis of medical records from Texas indicates that alcohol consumption reduces the risk of myocardial infarction and congestive heart failure but increases the risk of atrial fibrillation (AF).

Investigators compared hospital admission records of 1.1 million patients aged 21 years and older from counties that did and counties that did not allow the sale of alcohol between 2005 and 2010.

Compared to residents of “dry” counties, residents of “wet” counties (which allowed alcohol sales) suffered a lower prevalence (odds ratio [OR], 0.83; 95% confidence interval [CI], 0.79-0.87; P<0.001) and incidence (hazard ratio [HR], 0.91; 95% CI, 0.87-0.99; P=0.019) of myocardial infarction as well as a lower prevalence (OR, 0.87; 95% CI, 0.84-0.90; P<0.001) of congestive heart failure. The same analysis, which adjusted for multiple factors, also found that residents of wet counties faced a slightly greater comparative prevalence (OR, 1.05; 95% CI, 1.01-1.09; P=0.007) and incidence (HR, 1.07; 95% CI, 1.01-1.13; P=0.014) of AF.

Investigators paid particular attention to counties that liberalized their alcohol laws during the study period and transformed themselves from dry to wet. Such conversions resulted in significantly higher rates of alcohol misuse, alcoholic liver disease, AF and congestive heart failure but no difference in myocardial infarction.

“Atrial fibrillation was the only outcome that showed divergent results between the unadjusted numbers and the adjusted results in the intra-county analyses. Such results were in fact expected owing to two important considerations: firstly, dry county residents were older and more often male and non-Hispanic white, all particularly important risk factors for atrial fibrillation,” the study authors wrote in the British Medical Journal.

“Propensity based analyses also showed that atrial fibrillation was more common in wet counties. As this database tracked patients on their county of residence, and not by the location of the admitting hospital, these findings are unlikely to be explained by rural versus urban hospital referral patterns. These findings are further supported by our more robust intra-county before and after election analysis, which showed an increase in admissions for atrial fibrillation after the liberalization of drinking laws.”

The researchers noted that some, but not all, previous studies have found that more alcohol consumption is significantly associated with more AF. Previous findings about alcohol’s effects on cardiovascular health have been more complex. The balance of previous data suggested a protective effect against myocardial infarction but increased mortality from ischemic heart disease. Previous findings about alcohol’s effect on heart failure have likewise been mixed.

The investigators who conducted the new study acknowledged some limitations to their design — including its retrospective nature and some demographic differences between wet and dry counties &mdash; but argued that their study had several advantages over its predecessors. Most importantly, it did not use self-reported consumption data, which can be highly unreliable.

They also wrote that their study was the first to demonstrate the effect of alcohol sales laws on various aspects of public health and that their findings posed an interesting paradox.

“The discordant results, showing more atrial fibrillation but less myocardial infarction and congestive heart failure in wet compared with dry counties, are particularly remarkable given that these outcomes generally share all of the same risk factors and that each can lead to the other,” the study authors wrote. “Given these potential “downstream” influences, these discordant results may suggest that the direct effects of alcohol are more potent than the point estimates reported.”