Does moderate alcohol consumption protect your heart? Genetic study offers new answer
He gave them both well-accepted medical advice: An average of about one drink a day helps the heart.
“I didn’t think twice about it,” he said.
Then he saw an article published in JAMA Network Open whose findings changed his thinking about what to tell patients. The newspaper, he said, “totally changed my life”.
His conclusion: There is no level of alcohol consumption that does not confer risk of heart disease. The risk is low if people drink an average of seven drinks a week versus none. But it increases rapidly as the level of alcohol consumption increases.
“Dose matters a lot,” said Dr. Krishna G Aragam, a preventive cardiologist at Massachusetts General Hospital and author of the study. “Just realize that when you exceed modest limits, the risk increases enough.”
The study, which may help resolve medical disputes over the effects of alcohol on the heart, involved sophisticated analyzes of the genes and medical data of nearly 400,000 people who take part in the UK Biobank, a British repository that investigators use to study genes and their relationship to health. The average age of the subjects selected for the alcohol study was 57, and they reported consuming an average of 9.2 drinks per week.
Some researchers have reported that moderate drinking protects the heart because moderate drinkers as a group have less heart disease than heavy drinkers or abstainers. Aragam and his colleagues have also seen this effect. But the reason, they report, is not that alcohol protects the heart. It’s that light to moderate drinkers – those who drink up to 14 drinks a week – tend to have other characteristics that lower their risk, such as smoking less, exercising more and weighing less than those who drink. more and those who don’t drink.
It’s unclear why moderate drinkers tend to be healthier than nondrinkers, Aragam said. But the Biobank study didn’t ask why people were drinking or abstaining. Instead, he attempted to distinguish the effects of alcohol on the heart from the effects of other habits, behaviors and characteristics. To do this, the researchers used a method called Mendelian randomization.
Researchers have found genetic variants that predispose a person to drink more or less. Because variants are randomly distributed in a population, they can be used in a study as the equivalent of randomly assigning people to abstain or drink at varying levels. Researchers can ask whether those with variants linked to higher alcohol consumption have more heart disease and high blood pressure than those with variants linked to lower drinking.
The investigators’ statistical analysis showed an exponential risk curve with the genetic variants suggesting they drink more. range of 21 or more drinks per week.
The actual risks for an individual depend on whether or not the person has other conditions, such as diabetes or obesity. But, Aragam said, extrapolating from the study results, a typical middle-aged person in the study who wasn’t drinking had about a 9% chance of having coronary heart disease. A person who drank one drink a day had about a 10.5% chance, which is low. After that, however, the risk increases rapidly.
Many previous studies of alcohol consumption and heart health were observational, meaning subjects were followed over time to see if the amount of alcohol was related to heart health.
Such studies can only find correlations but not causation, the researchers say. But the Biobank study’s use of Mendelian randomization suggests more causation, and its findings may therefore carry more weight.
“We need to start thinking about these moderate ranges and informing patients accordingly,” Aragam said. “If you choose to drink, know that beyond a certain level, the risk increases a little. And if you choose to drink less, you’ll get the bulk of your benefits if you go down to seven drinks a week.
Dr. Amit V Khera, study author and cardiologist at Verve Therapeutics, said that, of course, the gold standard for assessing the cardiac effects of alcohol consumption would be a large randomized clinical trial. Such a study, which would have randomized high-risk people to one drink a day or abstinence, was planned for 2017 by the National Institutes of Health. But it was halted because the researchers had inappropriate contact with the alcohol industry when planning the study.
Mendelian randomization techniques, Khera said, “are particularly useful when a gold standard has not been or cannot be made.”
Despite the difficulties of doing a randomized trial of alcohol consumption, a recent study in Australia provided some clues. It involved 140 people with atrial fibrillation, a form of heart disease. At the start of the study, participants reported drinking an average of 17 drinks per week. A randomly selected group of 70 people were asked to abstain and managed to reduce their drinking to an average of two drinks per week. During the six-month study period, people in the control group had atrial fibrillation 1.2% of the time, compared with 0.5% for people randomized to abstain.
Hazen, the Cleveland cardiologist, said the new Biobank study made him wonder about the effects of increased alcohol consumption during the pandemic. Researchers have noted that people have been drinking more since the start of the pandemic, and a recent report found that the number of alcohol-related deaths increased by 25% in 2020.
Blood pressure has also increased during the pandemic. Hazen and his colleagues, looking at national data, found that it had risen by an average of almost 3 millimeters of mercury.
“We had no idea how it was going,” Hazen said.
Changes in participants’ body weights did not account for increases in blood pressure during the pandemic. The increase, which occurred in all 50 states and Washington, DC, was a headache.
Now he has a new thought.
“Oh my. Maybe the increase in alcohol consumption explains the increase in blood pressure,” Hazen said.
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