Exactly why and how alcohol seems to help preserve normal cognitive functioning isn't clear, experts say. It may increase the release of a neurotransmitter, acetylcholine, which helps brain cells communicate with each other.
The new results conflict with those from an earlier study, reported in 2007 in the journal Neurology, that found people with mild cognitive impairment might slow their mental decline with up to one drink a day.
The first finding in the new study -- the 37 percent reduction in dementia among cognitively healthy moderate drinkers -- "is a very substantial reduction," said Dr. Denis Evans, Jesmer Professor of Internal Medicine at the Rush Institute for Healthy Aging at Rush University Medical Center, in Chicago.
"This is consistent with other studies," he said.
As for the finding that those mildly impaired get no benefit or, if they drink more than moderately, increase their risk of dementia? There may not have been enough participants to definitively find a link, Evans said.
And, Evans added, what looks like a healthy effect of alcohol among those who are cognitively normal and drink may actually be due to something else. "Is it really the effect of the alcohol or the difference between people who drink and those who don't?'' he asked.
For instance, he said, older adults who drink alcohol moderately may be in better physical and mental shape. The healthy cognitive function that persists may be due to other lifestyle habits.
And, Evans added, "Alcohol consumption is something to be cautious about even though it seems to have some beneficial effects."
To learn more about the warning signs of Alzheimer's disease, visit the Alzheimer's Association.
SOURCES: Kaycee Sink, M.D
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