Light to moderate alcohol can also damage the brain

The study, using a dataset of more than 36,000 adults, revealed that drinking one to two drinks a day was associated with changes in the brain comparable to two years of aging. Drinking more alcohol is associated with even larger amounts.

The science of heavy drinking and the brain is clear: Heavy drinkers have changes in brain structure and size that have been linked to cognitive decline.

But according to a new study, drinking even at what most people consider modest — a few beers or glasses of wine a week — can 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 a reduction in overall brain volume.

The researchers showed that the association grew with greater alcohol consumption. For example, in 50-year-olds, when average interpersonal alcohol consumption increases from one unit of alcohol (about half a pint of beer) a day to two units (a pint of beer or a glass of wine), there are related changes in the brain. equivalent to two years of aging. Going two to three units of alcohol at the same age is like being three and a half years old. The team reported their findings in the journal Nature Communications.

The association grew as alcohol consumption increased.

'The fact that we have such a large sample size allows us to find subtle patterns, even between drink the equivalent of half a beer and a pint a day." 

Kranzler, who directs the Penn Center for Addiction Research, said: 'These findings contrast with government and scientific guidelines for safe drinking limits. "For example, although the National Institute on Alcohol Abuse and Alcoholism recommends that women consume no more than one drink per day on average, the recommended limit for men is twice as much, an amount that exceeds related to brain decline".

Abundant research has examined the link between alcohol consumption and brain health, with mixed results. Although there is clear evidence that heavy drinking causes changes in brain structure, including a sharp reduction in the gray and white matter of the brain, other studies have suggested that moderate drinking may not have an impact, or even that light drinking can benefit the brain in older adults.

However, previous investigations lacked the power of large data sets. Tracking large amounts of data for samples is the expertise of Nave, Davet and colleagues, who have performed previous studies using the UK Biobank, a dataset with genetic and medical information from half a million middle-aged British adults. They used biomedical data from this source in the current study, which specifically looked at brain MRIs from more than 36,000 adults in the Biobank, which can be used to calculate white matter and white matter volumes. gray in different regions of the brain.

Nave said: 'Having this dataset is like having a microscope or a telescope with a more powerful lens. You get better resolution and start seeing patterns and associations that you couldn't before."

To understand the possible link between alcohol consumption and the brain, it is important to control for confounding variables that could cloud the relationship. The team controlled for age, height, handedness, sex, smoking status, socioeconomic status, genetic ancestry, and county of residence. They also edited brain mass data for the overall size of the head.

Biobank volunteers responded to survey questions about their alcohol consumption, giving up alcohol altogether to an average of four or more units of alcohol per day. When the researchers grouped the participants by average consumption, a small but clear pattern emerged: The volume of gray and white matter that could be predicted by other characteristics of the individual decreased.

Going from 0 to 1 unit of alcohol doesn't make much of a difference in brain volume, but going from 1 to 2 or 2 to 3 units per day is associated with a reduction in both gray and white matter.

Davet says: 'It's not linear. "It gets worse the more you drink."

Even removing heavy drinkers from the analyses, the associations remained. The scientists found that lower brain volume was not concentrated in any brain regions.

To get a feel for the impact, the researchers compared the reduction in brain size associated with alcohol consumption with those with aging. Based on their model, each additional unit of alcohol consumed per day is reflected in a larger aging effect in the brain. While going from zero to a daily average of one unit of alcohol is associated with the equivalent of half a year of aging, the difference between zero and four drinks is more than 10 years of aging.

In the future, the authors hope to tap into the UK Biobank and other large datasets to help answer additional questions related to alcohol use. "This study looked at average consumption, but we were curious if drinking one beer a day was better than no beer during the week and then seven on the weekend," Nave said. "There's some evidence that drinking is bad for the brain, but we haven't looked at that closely."

They also want to be able to more clearly define causality rather than correlation, which is possible with new longitudinal biomedical data sets that are closely following young people as they age. .

"We can look at these effects over time and, together with genetics, identify different cause-and-effect relationships," says Nave.

And while the researchers stress that their study only looked at correlations, they say the findings may prompt drinkers to reconsider their intake.

There is some evidence to suggest that the effects of alcohol consumption on the brain are exponential. So, one additional drink in a day can have more impact than any previous drink that day. That means cutting back on last night's drinks could have a big effect on brain aging."

In other words: "the people who could benefit most from drinking less were the people who drank the most," says Nave.