At this point, we can safely confirm that booze is bad for the brain. The question on everyone’s mind, however, is how bad is it really? The vast majority of us leave binge drinking behind in college and our 20s. Surely knocking back a few drinks every week can’t really be that bad, right?
Well… a new study run by University of Pennsylvania researchers found that even light-to-moderate levels of alcohol consumption, like one drink a day, was associated with overall reductions in brain volume. That link only grew stronger as levels of alcohol intake grew.
And the study’s findings, published in Nature Communications, are only more alarming given that they encompass data from more than 36,000 adults—a sample size that’s far greater than earlier investigations probing the relationship between booze and brains.
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“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,” study co-author and UPenn professor Gideon Nave said in a press release.
Reduced brain volume leads to cognitive impairments. Brains naturally shrink with age, so brain size can act as a proxy measurement for brain age. Repeated brain injuries and some kinds of behaviors, including drinking, can further reduce brain size and accelerate brain aging.
The new study analyzes information from the UK Biobank, a repository of medical data from half-a-million British adults across different ages, sexes, socioeconomic statuses, genetic ancestries, places of residence, and many other health factors. Of the 36,000 participants in this study, Nave and his team specifically looked at how brain MRIs—which are very useful in illustrating overall brain volume—changed with respect to drinking habits.
“Having this dataset is like having a microscope or a telescope with a more powerful lens,” Nave said. “You get a better resolution and start seeing patterns and associations you couldn’t before.”
After controlling for factors that can affect brain size, Nave and his team found that elevated levels of drinking basically led to lower volumes of brain matter than what researchers otherwise predicted. Drinking an average of one unit of alcohol a day (about half a beer) was equivalent to accelerating aging of the brain by about half a year. The effect is exponential as you jump to higher levels of drinking: Four units of alcohol a day accelerated brain aging by more than 10 years.
And of course, actual biological age only compounds this relationship further. For a typical 50-year-old, one unit of alcohol a day increased brain aging by two years. Going from two to three drinks a day added another three-and-a-half years.
These findings could mean that governmental guidelines on safe drinking limits need some big revisions. The National Institute on Alcohol Abuse and Alcoholism, for example, recommends women consume no more than one drink per day, and a limit of two a day for men.
Revising those guidelines might first require a bit more research. Nave and his colleagues admit they will need to run more studies to confirm what they have found is a causal relationship between drinking and brain size, and not just correlation. And they’d also like to get a better sense of what kind of specific cognitive effects moderate drinkers might suffer compared to teetotalers.
But at the very least, the new findings are another reminder to think twice before you decide to splurge for that next drink—or maybe to just abstain altogether.
