In large amounts, alcohol is known to have adverse health effects. In small amounts, however, it can protect the heart from some types of heart disease. A new analysis suggests moderate, habitual drinking may not have the same protective effect when it comes to heart rate.
The adverse health effects of excessive alcohol consumption are very serious and widely known. The Centers for Disease Control and Prevention (CDC) report that heavy or binge drinking accounts for 88,000 yearly deaths in the United States.
Between 2006 and 2010, excessive alcohol consumption was responsible for a total of 2.5 million years of potential life lost, shortening the lives of those who died from an alcohol-related problem by 30 years.
However, a significant amount of research has suggested that moderate alcohol intake may have some health benefits.
According to the Dietary Guidelines for Americans, what counts as moderate drinking is up to one drink per day for women and up to two drinks per day for men.
However, a new review of these studies suggests moderate drinking may not have the same positive effects on the heart rate. Rather, even light to moderate drinking may lead to a form of arrhythmia.
Studying the link between irregular heartbeat and moderate drinking
A team of researchers in Melbourne, Australia, reviewed over 100 studies that show light-to-moderate alcohol consumption is good for some people and reduces the risk of heart disease.
Researchers were led by Prof. Peter Kistler, of Baker IDI Heart and Diabetes Institute, and the Alfred Hospital in Melbourne, Australia.
In total, the review included data on almost 900,000 people who were followed up for 12 years.
The meta analysis was published in the Journal of the American College of Cardiology.
Risk of irregular heartbeat increases with every drink
The analysis revealed that even light to moderate drinking may increase the risk of irregular heartbeat.
With every drink consumed per day, the risk of atrial fibrillation increased by 8 percent.
The risk of irregular heartbeat affected men and women equally.
The study's lead author explains the mechanism behind the numbers.
"While moderate amounts of alcohol appear protective for the 'plumbing' or blood supply to the heart muscle, the benefits of alcohol do not extend to the electrical parts of the heart or heartbeat. People who continue to consume alcohol at moderate rates may also notice their irregular heartbeats become more frequent. This is concerning, because it can lead to serious issues, such as heart failure and stroke."
Professor Peter Kistler
Although more research is needed to establish the cause of this association, the authors list some of the potential explanations.
Possible reasons for link between alcohol and irregular heartbeat
One cause might be the effect alcohol has on the cells. Drinking can lead to cell damage, which in turn means damage in small areas of the fibrous tissue within the heart. This could cause an irregular heartbeat.
Some patients who have a fast or arrhythmical heart rate that has not responded to medicine may undergo catheter ablation - a procedure where parts of the heart are selectively cauterized. The study also revealed that people who continue to drink after they have had catheter ablation are more likely to continue to have irregular heartbeat even after the procedure.
Atrial fibrillation could also be explained electrophysically. In a normally functioning heart, with every heartbeat an electrical signal gets sent off from the top to the bottom of the heart. This makes the heart contract and pump blood. Each electrical signal starts in a group of cells and travels in an organized fashion through the heart's pathways.
With time, alcohol may alter these electrical signals, which may lead to atrial fibrillation. In this type of arrhythmia, electrical signals travel through the heart's atria in a fast and chaotic way.
Finally, alcohol consumption can interfere with the autonomic nervous system. This part of the nervous system controls the body's heart rate, digestion, temperature, respiratory rate, and the body's "fight or flight" response in case of emergencies.
According to the review, alcohol stimulates this internal nervous system, which can lead to irregular heartbeat.
Moderate drinkers may not realize health risk
"The results are significant," Prof. Kistler says, "since there are people who are consuming one to two glasses of alcohol per day that may not realize they are putting themselves at risk for irregular heartbeat."
For Kistler, the takeaway is that "even though we do not have randomized data that tells us what a 'safe' amount is to consume, people with an irregular heartbeat should probably drink no more than one alcoholic drink per day with 2 alcohol-free days a week."
Authors note the need for more research to exactly determine the specific causes behind the association. They think that causal explanations may include the direct toxicity and alcohol's effect on obesity, disordered breathing during sleep, and hypertension.
Further research is also needed to establish whether total avoidance of alcohol is required for those patients who have atrial fibrillation.