Every drop counts.

When we think about alcohol's impact on the brain, we typically think in extremes. Binge drinking can alter brain anatomy and personality in teens, alcohol abuse can leave the brain struggling to repair damage weeks after going dry. Rarely do we consider the slow, measured effects of years of drinking on the brain, but new research is demonstrating just how much every drop counts.

According to an analysis of brain images taken from 11,651 participants in the UK Biobank, a national health register in the United Kingdom, every gram of alcohol consumed per day was linked to 0.02 years of brain aging — that's about a week of additional aging in the brain.

Cumulatively, people who reported drinking every day or on most days, had about 5 months (0.4 years) of additional aging in their brains compared to people who were the same chronological age as them, but reported less frequent drinking, the study finds. That suggests that their frequent drinking habit aged their brains at an accelerated rate.

Every gram of alcohol consumed per day linked to a week of additional aging in the brain

The good news is that these changes are relatively modest. Arthur Toga, the study's senior author and professor at University of Southern California, tells Inverse that it's unclear how these changes in the brain actually affect people's quality of life. But the bad news is that they're still significant.

"The 0.4 years of difference was statistically significant. We suggest that daily or almost daily alcohol consumption can be detrimental to the brain," Toga says.

The paper was published Thursday in the journal Scientific Reports.

What speeds up aging in the brain?

The researchers estimate Relative Brain Age using MRI scans gathered from 5,193 participants. The metric offers a way to compare brain aging amongst people who are all the same chronological age, and illuminate how outside influences can lead someone's brain to age at a different rate relative to their peers.

The scans record decreases in the brains white matter (densely connected nerve fibers that help usher electrical signals through the brain) grey matter (another type of brain tissue that wastes away as cognitive function declines) and other metrics related to brain volume associated with brain aging.

Each additional gram of alcohol per day was linked to about one week of aging in the brain, according to this analysis. VICTOR DE SCHWANBERG/Science Photo Library/Getty Images

How fast a person's brain ages depends on both genetics and the environment — and that includes our habits. In the study, the team zeroed in on smoking and drinking habits among 11,651 participants.

When it came to booze, the biggest effects on brain aging were seen in those who drank the most alcohol – people who reported drinking every day or on "most days". People who drank that much had brains about five months older on average than people of the same biological age who drank less frequently.

Cigarette smoking may have an even more dramatic aging effect, the study suggests. Each year spent smoking one pack of cigarettes per day led to about about 11 additional days (0.03 years) of brain aging, the team calculated. Over time, that meant that those who smoked most often — usually every day — had brains between 6-7 months older on average than those who smoked less frequently or not at all.

Giuseppe Barisano, a post-doctoral research fellow at USC tells Inverse that these differences in brain age may be clinically relevant for heavy drinkers or smokers in the future. Barisano has worked with Toga before, but was not involved in this current study.

"Even though plus 0.4 and plus 0.6 years of relative brain age may look small and not significant, these numbers are actually important, especially since they are associated with a corresponding and significant worse cognitive function," Barisano says.

Outperforming a changing brain

Though genetics are beyond our control, the study points to how lifestyle choices usher the brain down the path of aging. Some of the best ways to preserve the brain are also a matter of lifestyle changes.

The changes in Relative Brain Age weren't significantly higher between people who reported smoking "occasionally" and those who smoked every day or on most days, Barisano says. That suggests "some of the damages related to smoking can be stopped and in some cases even reverted by smoking cessation — for example, heart and blood vessel damage," he says.

Other research suggests we could help protect our brains and bodies not just by quitting bad habits, but by embracing good ones.

For example, a study published in December 2019 suggests that interventions like exercise and mantaining a "cognitively active" lifestyle can drastically slow the rate of cognitive decline, even in patients who carried a gene linked to a type of dementia that made drastic anatomical changes to their brain basically inevitable.

In a sample of 105 people with the gene, the researchers found that those who lived physically and cognitively active lives had 55 percent slower rates of decline compared to those who didn't live actively. If you are wondering, a cognitively active lifestyle included habits like reading, doing puzzles, going to cultural events or, in short, the active pursuit of learning new things.

Importantly, the study participants didn't seen any restoration of the brain volume they had lost. Instead, they were "outperforming" the brain volume they already had. They were able to do more with less.

In a previous interview with Inverse, that study's first author Kaitlin Casaletto called exercise and cognitively active lifestyles "the best current tools we have to prevent cognitive decline."

The research illuminates the fact that we're not completely powerless over how our brains age: our actions resonate in our brains over time, for better or worse.

Longevity Hacks is a regular series from Inverse on the science-backed strategies to live better, healthier, and longer without medicine.

HOW THIS AFFECTS LONGEVITY – Every gram of alcohol consumed was linked to .02 years of brain aging, about a week of additional aging on the brain. Over time, the results showed that drinking on all or most days resulted in a brain that was about 5 months older than someone who was the same chronological age, but didn't drink as much. Smoking made things worse, people who smoked every day had brains between 6 and 7 months older than non-smokers.

WHY IT'S A HACK – These changes may seem small, but they were significant enough to be associated with worse cognitive function, explained Giuseppe Barisano, a post-doctoral research fellow at USC.

SCIENCE IN ACTION – This hack is more about ditching some bad habits. Drinking every day, and especially smoking every day, have long lasting effects on brain health. These are tough habits to get under control, but the benefits of overcoming them are significant.

HACK SCORE – 🚬🚬🚬🚬🚬🚬(6/10 cigarettes. It's hard to quit, but these benefits are too big to ignore.)

Abstract: Brain age is a metric that quantifies the degree of aging of a brain based on whole-brain anatomical characteristics. While associations between individual human brain regions and environmental or genetic factors have been investigated, how brain age is associated with those factors remains unclear. We investigated these associations using UK Biobank data. We first trained a statistical model for obtaining relative brain age (RBA), a metric describing a subject’s brain age relative to peers, based on whole-brain anatomical measurements, from training set subjects (n = 5,193). We then applied this model to evaluation set subjects (n = 12,115) and tested the association of RBA with tobacco smoking, alcohol consumption, and genetic variants. We found that daily or almost daily consumption of tobacco and alcohol were both significantly associated with increased RBA (P < 0.001). We also found SNPs significantly associated with RBA (p-value < 5E-8). The SNP most significantly associated with RBA is located in MAPT gene. Our results suggest that both environmental and genetic factors are associated with structural brain aging.