Even light or moderate alcohol intake can be harmful to brain

A research, using a dataset of more than 36,000 adults, revealed that going from one to two drinks a day was linked with changes in the brain equivalent to aging two years.

Even light-to-moderate drinking is associated with harm to the brain. Heavier drinking was associated with an even greater toll. The science on heavy drinking and the brain is clear: The two don’t have a healthy relationship. People who drink heavily have alterations in brain structure and size that are associated with cognitive impairments.

But according to a new study, alcohol consumption even at levels most would consider modest—a few beers or glasses of wine a week—may also carry risks to the brain. An analysis of data from more than 36,000 adults, led by a team from the University of Pennsylvania, found that light-to-moderate alcohol consumption was associated with reductions in overall brain volume. The team reported their findings in the journal Nature Communications.
The link grew stronger the greater the level of alcohol consumption, the researchers showed. As an example, in 50-year-olds, as average drinking among individuals increases from one alcohol unit (about half a beer) a day to two units (a pint of beer or a glass of wine) there are associated changes in the brain equivalent to aging two years. Going from two to three alcohol units at the same age was like aging three and a half years.

“The fact that we have such a large sample size allows us to find subtle patterns, even between drinking the equivalent of half a beer and one beer a day,” says Gideon Nave, a corresponding author on the study and faculty member at Penn’s Wharton School. He collaborated with former postdoc and co-corresponding author Remi Daviet, now at the University of Wisconsin-Madison, and Perelman School of Medicine colleagues Reagan Wetherill—also a corresponding author on the study — and Henry Kranzler, as well as other researchers.
“These findings contrast with scientific and governmental guidelines on safe drinking limits,” says Kranzler, who directs the Penn Center for Studies of Addiction. “For example, although the National Institute on Alcohol Abuse and Alcoholism recommends that women consume an average of no more than one drink per day, recommended limits for men are twice that, an amount that exceeds the consumption level associated in the study with decreased brain volume,”

Ample research has examined the link between drinking and brain health, with ambiguous results. While strong evidence exists that heavy drinking causes changes in brain structure, including strong reductions in gray and white matter across the brain, other studies have suggested that moderate levels of alcohol consumption may not have an impact, or even that light drinking could benefit the brain in older adults.

Even removing the heavy drinkers from the analyses, the associations remained. The lower brain volume was not localised to any one brain region, the scientists found.To give a sense of the impact, the researchers compared the reductions in brain size linked with drinking to those that occur with aging. Based on their modeling, each additional alcohol unit consumed per day was reflected in a greater aging effect in the brain. While going from zero to a daily average of one alcohol unit was associated with the equivalent of a half a year of aging, the difference between zero and four drinks was more than 10 years of aging.

In future work, the authors hope to tap the UK Biobank and other large datasets to help answer additional questions related to alcohol use. “This study looked at average consumption, but we’re curious whether drinking one beer a day is better than drinking none during the week and then seven on the weekend,” Nave says. “There’s some evidence that binge drinking is worse for the brain, but we haven’t looked closely at that yet.”

(By Nicole Lee, Professor at the National Drug Research Institute, Curtin University and Rob Hester Professor, Melbourne School of Psychological Sciences, The University of Melbourne for The Conversationalcohol)