More booze, less brain: Link begins with just one drink per day on average

According to a new study, even light-to-moderate drinking is linked to brain damage. Researchers evaluated data from more than 36,000 participants and discovered a relationship between drinking and decreased brain capacity that starts at less than one alcohol unit per day (about half a beer) and increases with each successive drink.

Using a dataset of over 36,000 participants, the study discovered that increasing from one to two drinks per day was connected to brain alterations comparable to two years of ageing. Drinking more heavily was linked to a higher toll.

Heavy drinking and the brain have an unhealthy relationship, according to scientists. People who drink heavily have structural and size changes in their brains, which are linked to cognitive deficits.

However, a recent study suggests that even moderate alcohol usage, such as a few beers or glasses of wine a week, may pose a risk to the brain. Light-to-moderate alcohol intake was linked to reductions in total brain capacity, according to a study performed by a team from the University of Pennsylvania that looked at data from over 36,000 participants.

The researchers discovered that the association became stronger as the amount of alcohol consumed increased.

For instance, among 50-year-olds, increasing average daily drinking from one alcohol unit (about half a beer) to two units (a pint of beer or a glass of wine) causes brain alterations comparable to two years of ageing. At the same age, going from two to three alcohol units was like ageing three and a half years. The findings were published in the journal Nature Communications.

“The fact that we have such a big sample size allows us to discover subtle trends, even between drinking the equivalent of half a beer and one beer a day,” says Gideon Nave, a corresponding author on the research and Wharton School faculty member.

He worked alongside former postdoctoral researcher and co-corresponding author Remi Daviet, who is now at the University of Wisconsin-Madison, as well as Perelman School of Medicine colleagues Reagan Wetherill and Henry Kranzler, as well as other researchers.

“These findings contradict scientific and regulatory standards on safe drinking limits,” adds Kranzler, who is the director of the Penn Center for Addiction Studies. “For example, while the National Institute on Alcohol Abuse and Alcoholism recommends that women consume no more than one drink per day on average, men’s recommended limits are twice as high, exceeding the consumption level linked to lower brain capacity in the research.”

The relationship between drinking and brain health has been studied extensively, with mixed results. While there is strong evidence that heavy drinking causes structural changes in the brain, including significant reductions in grey and white matter throughout the brain, other studies have suggested that moderate alcohol consumption may have no effect, or even that light drinking may benefit the brain in older adults.

However, these previous studies lacked the power of massive datasets. Nave, Daviet, and colleagues have previously undertaken research utilising the UK Biobank, a dataset of genetic and medical information from half a million British middle-aged and older persons, to look for patterns in large amounts of data.

“Having this dataset is like having a microscope or a telescope with a more powerful lens,” Nave says. “You get a better resolution and start seeing patterns and associations you couldn’t before.”

It was necessary to adjust for confounding variables that may muddy the association in order to acquire an understanding of probable connections between drinking and the brain. Age, height, handedness, sex, smoking status, socioeconomic position, genetic heritage, and county of residency were all taken into account. They also adjusted the brain-volume data to account for the size of the entire head.

The Biobank’s volunteer members had answered survey questions on their alcohol usage levels, which ranged from total abstinence to an average of four or more units per day. When the researchers divided the subjects into groups based on their average consumption levels, they noticed a subtle but noticeable pattern: the grey and white matter volume that would ordinarily be predicted by the individual’s other features was lowered.

Rising from zero to one alcohol unit per day had no effect on brain volume, but going from one to two or two to three units per day was linked to grey and white matter decreases.

“It’s not linear,” says 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 localized to any one brain region, the scientists found.

The researchers compared the changes in brain size associated with drinking to those associated with ageing to get a feel of the impact. According to their calculations, each additional unit of alcohol drank each day resulted in a larger ageing impact in the brain. While going from zero to a daily average of one alcohol unit was related with a half-year of ageing, going from zero to four drinks was associated with more than ten years of ageing.

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.”

They’d also like to be able to more definitively pin down causation rather than correlation, which may be possible with new longitudinal biomedical datasets that are following young people as they age.

“We may be able to look at these effects over time and, along with genetics, tease apart causal relationships,” Nave says.

And while the researchers underscore that their study looked only at correlations, they say the findings may prompt drinkers to reconsider how much they imbibe.

“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.”

In other words, Nave says, “the people who can benefit the most from drinking less are the people who are already drinking the most.”