October 14th, 2008
What's good for the heart may hurt the brain, according to a new study of the effects of alcohol.
People who drink alcohol -- even the moderate amounts that help prevent heart disease -- have a smaller brain volume than those who do not, according to a study in the Archives of Neurology.
While a certain amount of brain shrinkage is normal with age, greater amounts in some parts of the brain have been linked to dementia.
"Decline in brain volume -- estimated at 2 percent per decade -- is a natural part of aging," says Carol Ann Paul, who conducted the study when she was at the Boston University School of Public Health. She had hoped to find that alcohol might protect against such brain shrinkage.
"However, we did not find the protective effect," says Paul, who is now an instructor in the neuroscience program at Wellesley College. "In fact, any level of alcohol consumption resulted in a decline in brain volume."
In the study, Paul and colleagues looked at 1,839 healthy people with an average age of about 61. The patients underwent magnetic resonance imaging (MRI) of the brain and reported how much they tippled. Health.com: Ten best foods for the heart
Overall, the more alcohol consumed, the smaller the brain volume, with abstainers having a higher brain volume than former drinkers, light drinkers (one to seven drinks per week), moderate drinkers (eight to 14 drinks per week), and heavy drinkers (14 or more drinks per week).
Men were more likely to be heavy drinkers than women. But the link between brain volume and alcohol wasn't as strong in men. For men, only those who were heavy drinkers had a smaller brain volume than those who consumed little or no alcohol.
In women, even moderate drinkers had a smaller brain volume than abstainers or former drinkers. Health.com: Six reasons why a little glass of wine each day may do you good
It's not clear why even modest amounts of alcohol may shrink the brain, although alcohol is "known to dehydrate tissues, and constant dehydration can have negative effects on any sensitive tissue," says Paul.
"We always knew that alcohol at higher dosages results in shrinking of the brain and cognitive deficit," says Dr. Petros Levounis, M.D., director of the Addiction Institute of New York at St. Luke's -- Roosevelt Hospital Center, who was not involved in the study. "What is new with this article is that it shows brain shrinking at lower doses of alcohol." Health.com: Type 2 diabetes and alcohol: Proceed with caution
However, the study did not demonstrate that the smaller brain volume actually impaired memory or mental function, notes James Garbutt, M.D., professor of psychiatry at the University of North Carolina at Chapel Hill.
And the differences between brain volumes in drinkers and nondrinkers were quite small -- less than 1.5 percent between abstainers and heavy drinkers.
"We're talking very small differences here," says Dr. Garbutt, who was not involved in the study. "We're not seeing 10 to 20 percent shrinkage."
However, he says, reduction in brain mass is an interesting finding. "But we have a long way to go to figure out the implications of it."