Increasing alcohol intake was associated with loss in total brain volume greater than expected from age alone (P<0.001), reported Carol Ann Paul, of Wellesley College, and colleagues in the October issue of the Archives of Neurology.
In the cross-sectional study, women were affected more strongly than men by moderate alcohol intake averaging one to two drinks a day (eight to 14 per week).
The cardiovascular benefits of low to moderate alcohol intake are thought to result from increasing blood flow rates, which would have been expected to benefit the brain also, Paul said.
But rather than preventing normal age-related volume reductions, the effects of moderate drinking were closer to those of heavy drinking, which has been linked to brain atrophy and cognitive decline, the researchers noted.
Since declines in brain volume and increases in white matter lesions are associated with memory loss and worsening dementia, the effects of alcohol likely have some functional impact over time, Paul said.
"The brain shrinkage that you see with Alzheimer's and dementia is of a much greater magnitude," she said. "However, any decrease in brain volume is probably not beneficial."
They analyzed self-reported alcohol intake for 1,839 participants in the community-based Framingham Offspring Study who had an MRI between 1999 and 2001 but no clinically evident neurological disease, stroke, or dementia.
Most participants reported drinking one to seven alcoholic beverages a week, which is considered low intake. Men were more likely to report moderate or high -- more than 14 drinks per week -- alcohol consumption.
Increasing alcohol consumption was associated with decreasing total cerebral brain volume, which remained significant after adjustment for head circumference, age, sex, education, body mass index, and Framingham Stroke Risk Profile score (P<0.01).
The slope of this negative association (âˆ’0.25) was slightly greater than that for the average annual decline expected with aging.
Moderate drinking had a significantly worse impact on the brain than former drinking (P=0.03).
Heavy drinking was associated with significantly smaller brain volume compared with all other groups (P<0.01 versus abstinence, former drinking, and low intake, P=0.04 versus moderate intake).
Although the associations between alcohol consumption and brain volume were significant for both men and women (P=0.02 for both), there was a small difference with a steeper slope for women showing larger brain volume losses than men at every level of alcohol consumption (âˆ’0.29 versus âˆ’0.20, P<0.01 for interaction).
The explanation may be behavioral -- nearly twice as many men as women reported heavy drinking -- or biological, the researchers said. They noted that women absorb alcohol more rapidly, have less blood to dilute the alcohol on average, and generally are more vulnerable to the effects of alcohol.
No category of alcohol consumption was linked to white matter lesions seen on MRI.
The researchers noted that the findings may have limited generalizability because the study had a predominantly well-educated, Caucasian population.
Other limitations include the difficulty of distinguishing alcohol's effects from those of age and potential underreporting of drinking, although this would only have underestimated the association, they said.
Importantly, they noted, the cross-sectional nature of the study could not draw a causal link between alcohol consumption and a decline in brain volume.
Until it can be confirmed in prospective studies that there are clinical effects on cognition, it may be best to stick with the cardiovascular guidelines recommending a glass of wine a day, Paul suggested.
But "the public health effect of this study gives a clear message about the possible dangers of drinking alcohol," they concluded.
|The study was supported by a contract from the National Heart, Lung, and Blood Institute's Framingham Heart Study and grants from the National Institute on Aging and the National Institute of Neurological Disorders and Stroke.
The researchers reported no conflicts of interest.
Zalman S. Agus, MD Emeritus Professor
University of Pennsylvania School of Medicine
Archives of NeurologySource Reference: Paul CA, et al "Association of Alcohol Consumption With Brain Volume in the Framingham Study" Arch Neurol 2008; 65: 1363-1367.