VIENNA — A drink or two a day seems to protect against the development of dementia in cognitively normal elderly adults, a study suggests.
But moderate alcohol consumption doesn't improve thinking processes in those who already have mild cognitive impairment (MCI), and heavy drinking can tip the scales from mild impairment to dementia, Dr. Kaycee M. Sink said at the International Conference on Alzheimer's Disease.
“Our findings support current recommendations for alcohol consumption [of one drink per day for women and two for men], at least for older adults with normal cognition,” Dr. Sink said in an interview.
However, she warned, alcohol's brain benefit can't be used as an excuse to take up drinking at an advanced age. “The results of our study apply only to older adults who reported drinking alcohol at the start of the study. They can't be extrapolated to those who do not currently drink—that is, we cannot recommend that someone in his 70s or 80s start drinking alcohol to try to prevent dementia,” said Dr. Sink of Wake Forest University, Winston-Salem, N.C.
Dr. Sink and her colleagues based their study on data extracted from the Ginkgo Evaluation of Memory (GEM) study, which enrolled 3,069 participants aged 75 or older with normal cognition or mild cognitive impairment. They were randomized to twice-daily doses of either placebo or 120 mg of ginkgo extract. Although the extract was safe, it was not associated with any significant cognitive improvement (JAMA 2008;300:2253-62).
At baseline, the subjects' average age was 78 years; 2,587 were cognitively normal, and 482 had MCI. MCI was present in 20% of the alcohol abstainers and 12% of the consumers.
Subjects self-reported daily alcohol consumption as abstinent, light (1-7 drinks/week), moderate (8-14 drinks), or heavy (more than 14 drinks). Abstinence was reported by 43%, light drinking by 38%, moderate drinking by 9%, and heavy drinking by 10%.
There were 523 new cases of dementia during the 6-year follow-up period. After adjusting for demographics, smoking, medical comorbidities, depression, social activity, and baseline cognition, moderate alcohol consumption conferred a 37% reduction in the risk of dementia in those who were cognitively normal at baseline. But moderate drinking did not reduce the dementia risk for those who already had MCI at baseline.
Heavy drinking conferred a nonsignificant 18% risk reduction for cognitively normal subjects. But in those who already had MCI, heavy drinking significantly increased by 92% the risk of progression to dementia. “Heavy alcohol use is associated long-term toxic effects in the brain. In addition to the almost twofold increase in risk of progression to dementia for participants with MCI who drank heavily, we saw that even lesser amounts of alcohol were associated with greater declines in a measure of overall cognition over the 6-year study,” she said.
The protective mechanism of mild drinking remains a mystery, she said. “We don't fully understand how alcohol may be protective against dementia. However, since for many people, MCI is a transition state between normal cognition and dementia, it may be that any protective benefits from moderate alcohol intake are too late once the process of cognitive impairment begins. Alternatively, the results could be consistent with the cognitive reserve hypothesis, in that those who are already declining aren't as resilient to neurotoxic effects of heavy alcohol use as cognitively normal older adults might be.”
Dr. Sink said she had no conflicts of interest with regard to the study.
Moderate drinking did not reduce the dementia risk for those who already had mild cognitive impairment at baseline.
Source DR. SINK