New research has found a correlation between even modest levels of alcohol consumption and reduced brain size.
Led by the , the study of more than 36,000 adults associated reduced grey and white matter in the brain to drinking even a few beers or glasses of wine a week.
The research shows for 50-year-olds, going from one alcohol unit or about half a beer a day to two units, such as a pint of beer or glass of wine, was the equivalent of aging two years.
Meanwhile, going from two to three alcohol units at the same age was similar to aging 3.5 years.
The researchers say the findings contrast with guidelines on safe drinking limits, including recommendations that women consume no more than one drink per day on average, or double that for men.
The study was published in the journal Nature Communications.
"The people who can benefit the most from drinking less are the people who are already drinking the most," said Gideon Nave, a corresponding author on the study and faculty member at Penn's Wharton School.
The study's authors say past research has examined the link between drinking and brain health, including reported reductions in grey and white matter. Other studies also have suggested moderate alcohol consumption may not have an impact on the brain or that light drinking could benefit older adults.
The researchers, however, say those earlier investigations lacked large datasets.
The latest research used biomedical data from the U.K. Biobank, which contains genetic and medical information from half a million middle-aged and older British adults.
The team also controlled for age, height, handedness, sex, smoking status, socioeconomic status, genetic ancestry and county of residence.
Volunteer participants in the Biobank responded to survey questions about their alcohol consumption, ranging from abstention to an average of four or more alcohol units per day.
The researchers found while going from zero to one alcohol unit didn't have much of an impact on brain volume — the equivalent of aging half a year — going from one to two, or two to three drinks, resulted in a greater aging effect.
Going from zero to four drinks per day on average, for example, was the equivalent of aging more than 10 years.
"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 said.
"There's some evidence that binge drinking is worse for the brain, but we haven't looked closely at that yet."
The researchers say longitudinal studies, following young people as they age, may help determine causation rather than correlation.
