Alcohol and the human brain don’t have a healthy relationship.
People who drink heavily undergo alterations in brain structure and size, both of which are associated with cognitive impairments, a new study released on Friday suggests.
Even modest alcohol consumption, which is defined as a few beers or glasses of wine weekly, may also carry risks to the brain.
The study, which was led by a team from the University of Pennsylvania, looked at more than 36,000 adults, found that light-to-moderate alcohol consumption was associated with reductions in overall brain volume.
The links grew stronger the greater the alcohol consumption.
One drink a day linked to a smaller brain, aging two years
In 50 year olds, as average drinking among individuals increases from one alcohol unit, which is defined as about half a beer a day, to two units, which is defined as a pint of beer or a glass of wine, there are associated changes in the brain equivalent to aging two years. And going from two to three alcohol units at the same age was like aging three and a half years, the team reported 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,” says Gideon Nave, a faculty member at Penn’s Wharton School who was an author on the study.
“These findings contrast with scientific and governmental guidelines on safe drinking limits,” says Henry Kranzler, who directs the Penn Center for Studies of Addiction and is an author on the study. “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.”
Strong evidence exists that heavy drinking causes changes in brain structure, including strong reductions in gray and white matter across the brain, while 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 lacked the power of large datasets. The authors looked at brain MRIs from more than 36,000 British adults, in an attempt to calculate white and gray matter volume in different regions of the brain.
The volunteer participants 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 gray 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 gray and white matter.
“It gets worse the more you drink”
“It’s not linear,” says Remi Daviet, an author on the study. “It gets worse the more you drink.”
Even removing the heavy drinkers from the analyses, the associations remained. The lower brain volume was not localized to any one brain region, the scientists found.
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.
“There is some evidence that the effect of drinking on the brain is exponential,” says Daviet. “So, one additional drink in a day could have more of an impact than any of the previous drinks that day. That means that cutting back on that final drink of the night might have a big effect in terms of brain aging.”
“The people who can benefit the most from drinking less are the people who are already drinking the most,” Nave says.