Written by Dr. Nathan Herrmann, Lewar Chair in Geriatric Psychiatry and Head of the Division of Geriatric Psychiatry at Sunnybrook.
Question: Does alcohol consumption prevent Alzheimer's disease?
Answer: The studies on the effect of alcohol consumption and the risk of dementia are complicated, confusing, and conflicted. What is known for sure is that prolonged and excessive alcohol use can lead to dementia and other neurological complications. What is much less clear is whether light or moderate drinking might actually prevent dementia.
To answer the question about the possible effects of alcohol consumption on preventing Alzheimer's disease, it's important to understand how these studies were done. The studies looking at alcohol use are generally observational in nature. They pick a given population without dementia, ask them about their alcohol intake, and then follow them over time to see who develops dementia.
As you might imagine, it can be challenging for researchers to characterize the amount of alcohol consumed, because subjects often underestimate (purposely or subconsciously) the amount they drink. Different subjects will vary in terms of the pattern of drinking (e.g. daily vs weekly binging) and the type of alcohol they drink (e.g. spirits vs wine vs beer). All of these could affect the relationship between alcohol and dementia risk.
Most importantly however, while these observational studies might suggest there is a link between modest alcohol consumption and a decreased risk of dementia, establishing a direct causal (cause and effect) link between the two is impossible. The reason for this is that alcohol consumption might be associated with other, perhaps more important factors that reduce the risk of dementia. For example, modest drinking is also likely associated with greater social contacts, and social stimulation itself likely protects against dementia.
In terms of the type of alcohol that might be most likely to provide some protective benefit, red wine has received the most attention.
There have been numerous studies over the past few decades investigating this association described above. When the results of these studies are combined, it appears that light-to-moderate alcohol consumption is associated with about a 25 per cent reduction in the risk of Alzheimer's disease and other dementias compared to people who are non-drinkers.
The risk of dementia then increases in those who are heavy drinkers. However, as an example of how conflicting the results of these studies can be, there are two studies, both published in 2015, and both using data from Norway, that come to different conclusions.
In the first study of over 25,000 Norwegians followed for up to 17 years, the risk of dementia was significantly higher in abstainers. In the second study of over 40,000 Norwegians followed for up to 27 years, abstaining from alcohol was not found to increase the risk of dementia, though drinking frequently (defined as more than five times in the previous 14 days) was associated with an increased risk of developing Alzheimer's disease or other dementias.
In terms of the type of alcohol that might be most likely to provide some protective benefit, red wine has received the most attention. Red wine contains a compound called resveratrol, that has been associated with numerous (though largely unsubstantiated) benefits including protecting against heart disease and even increasing longevity. A recent study of resveratrol for patients with Alzheimer's disease however, failed to demonstrate any clear evidence of benefit and was actually associated with greater brain shrinkage.
While my primary clinical and research practice is devoted to Alzheimer's disease and memory disorders, my training as a psychiatrist has certainly coloured my opinions about alcohol use. For prevention purposes, I would clearly prefer that my patients avoid alcohol use, and engage in a "brain healthy lifestyle" which includes exercise, mentally stimulating activities and a Mediterranean type diet. When I'm asked specifically about alcohol intake, I generally recommend avoiding regular use, and certainly no more than one drink per day. Once I have diagnosed dementia, I stress the absolute need for abstinence given the harmful effects alcohol can have on the brain, memory and behaviour once dementia is present.
Read more from the Memory Doctor at health.sunnybrook.ca
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