According to a new study, alcohol consumption even at levels most would consider modest—a few beers or glasses of wine a week—may 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 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 ageing two years. Going from two to three alcohol units at the same age was like ageing three and a half years. The team reported their findings in the journal Nature Communications.
“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,” said 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,” said 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 grey 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.
These earlier investigations, however, lacked the power of large datasets. Probing massive quantities of data for patterns is the specialty of Nave, Daviet, and colleagues, who have conducted previous studies using the UK Biobank, a dataset with genetic and medical information from half a million British middle-aged and older adults. They employed biomedical data from this resource in the current study, specifically looking at brain MRIs from more than 36,000 adults in the Biobank, which can be used to calculate white and grey matter volume in different regions of the brain.
“Having this dataset is like having a microscope or a telescope with a more powerful lens,” Nave explained. “You get a better resolution and start seeing patterns and associations you couldn’t before.”
The volunteer participants in the Biobank had responded to survey questions about their alcohol consumption levels, from complete abstention to an average of four or more alcohol units a day. When the researchers grouped the participants by average-consumption levels, a small but apparent pattern emerged: the grey and white matter volume that might otherwise be predicted by the individual’s other characteristics was reduced.
Going from zero to one alcohol units didn’t make much of a difference in brain volume, but going from one to two or two to three units a day was associated with reductions in both grey and white matter.
“It’s not linear,” said Daviet. “It gets worse the more you drink.”
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 ageing. Based on their modeling, each additional alcohol unit consumed per day was reflected in a greater ageing 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 ageing, the difference between zero and four drinks was more than 10 years of ageing.
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 commented. “There’s some evidence that binge drinking is worse for the brain, but we haven’t looked closely at that yet.”
