May 1 (HealthDay News) -- Moderate drinking can lower the risk of dementia in older people, new research shows.
"Amongst cognitively normal adults, one to two alcoholic drinks a day is associated with a 37 percent decreased risk of dementia over six years," said senior study author Dr. Kaycee Sink, an assistant professor of medicine in geriatrics at the Wake Forest University School of Medicine, in Winston-Salem, N.C.
But among those in the study who had mild cognitive impairment to start with, drinking moderately had no effect. And heavier drinking -- two or more a day -- nearly doubled their risk of developing dementia during the six-year follow-up.
Sink presented her findings Thursday at the American Geriatrics Society annual meeting, in Chicago.
Sink, along with study author Dr. Deanna Mangieri, a clinical geriatric fellow at Wake Forest University, and their colleagues looked at 3,069 men and women, average age 79, and followed them for six years.
At the study start, 2,587 were evaluated as cognitively normal; 482 had mild cognitive impairment, which can progress to dementia.
The researchers asked about alcohol intake, smoking, depression, social activity and other factors, and tested the participants' cognitive functioning at the end of the study.
About 38 percent of the participants had one to seven drinks a week, while about 9 percent had eight to 14 drinks a week.
The bottom line, according to Sink: "If you are cognitively normal, there is no reason you should avoid light to moderate use of alcohol, and it may be beneficial. But if you have memory problems, we would probably say any amount of alcohol may be hazardous for your cognitive functioning. If you already have some memory problems, drinking is not going to help prevent progression to dementia, and may accelerate your progression."
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."
SOURCES: Kaycee Sink, M.D., assistant professor, medicine in geriatrics, Wake Forest University School of Medicine, Winston-Salem, N.C.; Denis Evans, M.D., Jesmer Professor of Internal Medicine, Rush Institute for Healthy Aging, Rush University Medical Center, Chicago; April 30, 2009, presentation, American Geriatrics Society annual meeting, Chicago