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This means that while four teetotallers in 100 might develop atrial fibrillation over the period of the study, five per 100 might develop the condition if they consumed alcohol starting with slightly more than an alcoholic drink a week and more than 75% of them consumed up to one drink a day [2]. The researchers categorised one alcoholic drink as containing 12 g of ethanol, which is the equivalent of a small (120 ml) glass of wine, a small beer (330 ml) or 40 ml of spirits.
It is well known that people who drink a lot of alcohol regularly are at increased risk of developing heart failure, and heart failure can increase the incidence of atrial fibrillation. Several studies have shown a slightly higher risk of heart problems for people who never drink alcohol; they often show that this risk reduces for people who drink a modest amount, and then rises sharply the more alcohol is consumed, creating a ‘J’ shape on graphs. Until now, it has not been clear whether this was also the case for atrial fibrillation.
However, in the current study led by Professor Renate Schnabel, a consultant cardiologist at the University Heart and Vascular Center, Hamburg-Eppendorf (Germany), researchers found that although low doses of alcohol were associated with a reduced risk of heart failure compared to teetotallers, a similar ‘J’ shape reduction in risk was not seen for atrial fibrillation. This suggests that the increased risk of atrial fibrillation among people drinking small amounts of alcohol was not triggered by heart failure.
Heart failure
The researchers analysed information on 107,845 people taking part in five community-based studies in Sweden, Norway, Finland, Denmark and Italy. The participants underwent medical examinations at the time they joined the studies between 1982 and 2010 and provided information on their medical histories, lifestyles, employment and education levels. A total of 100,092 participants did not have atrial fibrillation when they enrolled and their median age was nearly 48 years (range 24-97 years).
During the median follow-up period of nearly 14 years, 5,854 people developed atrial fibrillation. The associations between alcohol consumption and the risk of atrial fibrillation were similar for all types of alcoholic drinks and for men and women.
In addition to the 16% increased risk of atrial fibrillation compared to teetotallers seen in people who consumed only one alcoholic drink a day, the researchers found that the risk increased with increasing alcohol intake; up to two drinks a day was associated with a 28% increased risk and this went up to 47% for those who consumed more than four.
The exact mechanisms by which modest amounts of alcohol could trigger atrial fibrillation are not known. Studies have shown that heavy drinking over a short period of time can trigger ‘holiday heart syndrome’ in some people, and in some atrial fibrillation patients, small amounts of alcohol can trigger arrhythmia episodes.
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