The ISFAR reviewed recent research into the link between alcohol and dementia

A number of epidemiologic studies have found that light-to-moderate alcohol intake is associated with a lower risk of developing dementia and/or cognitive decline, while excessive drinking may increase the risk.

A recent research paper comprised a meta-analysis of the current scientific literature that was based on data from 11 studies, with 4,586 cases of all-cause dementia diagnosed among more than 70,000 subjects and two additional analyses of studies of approximately 50,000 subjects each for evaluating the association of alcohol intake with the diagnosis of Alzheimer's disease or vascular dementia.

Seven studies provided results according to the type of alcohol consumed, while two provided results according to APOE 4 levels.

The paper's conclusions were that considering all sources of alcohol, light-to-moderate alcohol consumption was associated with a lower risk of all forms of dementia; the risk was reduced for up to 12.5 g/day (about one typical drink) and increased for consumers of more than 38 g/day (about 3 to 4 typical drinks). However, beverage-specific analyses indicated that the effect was only for wine, and not for beer or spirits.

For moderate consumers of wine, the risk of dementia was reduced by 40% or more in comparison with that of non-drinkers. Little effect was noted among drinkers of spirits, and heavy beer drinkers appeared to have an increased risk of dementia. The presence or absence of APOE 4 did not appear to modify the effects.

ISFAR reviewers considered this to be a very well-done meta-analysis of the current literature on the topic. It was based only on prospective epidemiologic studies of very good quality, and sub-analyses evaluated the separate effects of each type of alcoholic beverage. While the authors were unable to include the pattern of drinking (binge versus regular/moderate) in their analyses, and could not test for previous alcohol consumption among current non-drinkers, ISFAR members agreed with the primary findings of a J-shaped curve between alcohol consumption and all types of dementia (including vascular dementia and Alzheimer's disease).

Most of this critique deals with potential mechanisms by which wine consumption may reduce the risk of dementia and/or cognitive decline. In addition to the effects of both alcohol and polyphenols in wine on decreasing atherosclerosis and having beneficial effects on hematological factors (affecting cerebral as well as coronary arteries), there may also be anti-inflammatory effects and direct effects on brain structures that play a role.

Given that the beneficial effects were primarily among wine consumers, this suggests that the polyphenols and other non-alcohol substances in wine (perhaps in interaction with alcohol) may be more important than the alcohol itself in reducing the risk of dementia.

The mechanistic studies described in the paper and in this critique provide considerable support for the epidemiologic findings of less dementia and cognitive decline among moderate drinkers. Our forum members agree with the authors of this paper that light-to-moderate wine consumption may help lower the risk of dementia, an increasingly-important condition in the world's rapidly ageing populations.

To read the full critique, click here.

These critiques are published with the permission of The International Scientific Forum on Alcohol Research.