LOS ANGELES: Even moderate alcohol consumption - having just one drink a day - over a long period of time may damage the heart and increase risk of stroke, a new study has warned.
"There's growing evidence that moderate alcohol intake may be a risk factor for atrial fibrillation, the most common heart rhythm disturbance in the world, but the mechanism by which alcohol may lead to atrial fibrillation is unknown," said Gregory Marcus, professor at University of California, San Francisco (UCSF).
Atrial fibrillation is a known risk factor for stroke. The irregular pumping of blood can lead to blood clots, which may travel to the brain and cause stroke.
Researchers looked at damage to the left atrium of the heart as a possible pathway between alcohol and atrial fibrillation.
The researchers evaluated data from more than 5,000 adults collected over several years including echocardiograms, medical history and self-reported alcohol intake.
The study participants, mostly white and in their 40s to 60s, reported on average just over one drink per day.
The overall rate of atrial fibrillation in the group was 8.4 cases per 1,000 people per year - meaning over a 10-year period, eight out of 100 people were likely to develop atrial fibrillation.
Every additional drink per day was associated with a 5 per cent increase in the yearly risk.
It was also associated with a statistically significant 0.16 millimetre enlargement of the left atrium, highlighting a possible site of physical damage caused by drinking.
The new findings shed light on the complex relationship between alcohol and heart health - one that likely precludes blanket advice on drinking habits, said Marcus.
Previous research has shown that moderate drinking can reduce the risk of heart attack while increasing the risk of atrial fibrillation.
Marcus's team found that patients in counties permitting alcohol sales were more likely to have atrial fibrillation but less likely to have heart attacks and congestive heart failure.
Alcohol's abilities to protect and harm the heart likely operate through different mechanisms and vary from person to person, said Marcus.
The work in his group seeks to decipher these mechanisms, which will inform therapies for heart conditions and may ultimately enable physicians to give personalised advice to patients.
The study appears in the Journal of the American Heart Association.