Alcohol Consumption, Dementia and Cognitive Decline: An Overview of Systematic Reviews.

There is uncertainty in relation to the effect of alcohol consumption on the incidence of dementia and cognitive decline. This review critically evaluated published systematic reviews on the epidemiology of alcohol consumption and the risk of dementia or cognitive decline. MEDLINE, EMBASE and PsycINFO were searched from inception to February 2014. Systematic reviews of longitudinal observational studies were considered. Two reviewers independently completed the 11-item Assessment of Multiple Systematic Reviews (AMSTAR) tool to assess the quality. We identified three moderate quality systematic reviews (AMSTAR score 4-6) that included a total of 45 unique studies. Two of the systematic reviews encompassed a meta-analysis. Light to moderate drinking may decrease the risk of Alzheimer's disease (AD) (pooled risk ratio [RR] 0.72; 95% confidence interval [CI] 0.61-0.86) and dementia (RR 0.74; 95%CI 0.61-0.91) whereas heavy to excessive drinking does not affect the risk (RR 0.92; 95%CI 0.59-1.45 and RR 1.04; 95%CI 0.69-1.56, respectively). One systematic review identified two studies that reported a link between alcohol consumption and the development of AD. No systematic review categorised former drinkers separately from lifetime abstainers in their analysis. Definitions of alcohol consumption, light to moderate drinking and heavy-excessive drinking varied and drinking patterns were not considered. Moderate quality (AMSTAR score 4-6) systematic reviews indicate that light to moderate alcohol consumption may protect against AD and dementia. However, the importance of drinking patterns and specific beverages remain unknown. There is insufficient evidence to suggest abstainers should initiate alcohol consumption to protect against dementia.