People who drink more than 30 grams of alcohol per day (about four drinks, regardless of the type of alcohol) have a higher risk of atrial fibrillation (AF) in reverse proportion to their ability to metabolize alcohol.

Also, the risk of AF increases by 1 percent for every additional drink per day regardless of alcohol metabolizing capacity, a study has shown.

The Seoul National University Hospital (SNUH) said Thursday that a team of researchers, led by Dr. Oh Se-il, a professor of Cardiac Electrophysiology and clinical instructor Park Chan-soon, analyzed the risk of AF according to alcohol metabolism and average daily alcohol consumption in more than 40 people enrolled in the U.K. Biobank Cohort from 2006 to 2010.

AF is a type of arrhythmia in which the heart contracts irregularly and is a major risk factor for stroke, dementia, and heart failure. Its prevalence is increasing worldwide as the population ages. The main symptoms are palpitations, chest discomfort, and, in severe cases, dizziness and shortness of breath.

It is well known that the risk of AF increases due to unhealthy lifestyles, such as smoking, obesity, and lack of exercise. Still, the relationship between alcohol consumption and AF risk has not been clearly understood. The researchers hypothesized that a person's genetic ability to metabolize alcohol may affect their risk of developing AF, regardless of how much they drink.

They also categorized 399,329 people without a history of AF into nondrinkers (0 grams), light to moderate drinkers (<30 grams, about less than four drinks), and heavy drinkers (≥30 grams, about four or more drinks) based on their average daily alcohol consumption. Each group was then further categorized into low, moderate, and high-risk groups based on a multigene risk score that quantifies "alcohol metabolizing capacity," and the risk of new-onset AF was followed for about 12 years.

The results showed that the "low alcohol metabolizer" group had the greatest risk of AF and that the association between alcohol consumption and AF risk varied by alcohol metabolizer. While the risk of AF decreased with increasing alcohol metabolizing capacity in heavy drinkers, this was not seen in light to moderate drinkers and nondrinkers.

In other words, alcohol metabolism may help identify individuals who are more susceptible to AF for the same amount of alcohol consumed and could be used as a basis for aggressively recommending abstinence in clinical practice, the researchers emphasized.

There was also a significant association between alcohol consumption and the risk of AF, regardless of alcohol metabolism. For every additional 8 grams of alcohol consumed per day (about one drink, regardless of alcohol type), the risk of AF increased by 1 percent.

"The risk of AF varies among people who consume the same amount of alcohol, so people who are less able to metabolize alcohol and therefore more susceptible to AF should positively stop drinking," Professor Oh said.