What is already known? Observational studies suggest that the alcohol-dementia relationship is likely to be J-shaped, with low levels of alcohol appearing to reduce and heavy consumption to increase the dementia risk compared with abstinence.
What does this study add? While the evidence for the J-shaped alcohol-dementia relationship is large, prior meta-analyses have several limitations: lack of standardization in terms of alcohol categorization, the abstaining group is often comprised of both former drinkers and life-time abstainers and there is a focus on high-income countries. The current meta-analysis addresses these limitations by harmonizing individual participant-level data, by taking into account life-time abstainers and former drinkers and by including studies in countries situated throughout six continents.
Lower risk up to 40 g of alcohol a day
When compared with abstainers, the risk for dementia was about 20% lower when consuming alcohol in amounts up to 40 g a day. The evidence was stronger for men than for women. In 11 of the 15 cohorts included, life-time abstainers could be separated from former drinkers. There was no significant difference in dementia risk between life-time abstainers and former drinkers.
Among current drinkers, there was no consistent evidence to suggest that the amount of alcohol consumed in later life was significantly associated with dementia risk. When analyzed at continent level, there was considerable heterogeneity in the alcohol-dementia relationship.
Findings need to be balanced
Experimental evidence in animal models is consistent with the findings of this meta-analysis, confirming the neurotoxicity of heavy alcohol consumption and the protective effects of alcohol at low doses.2-4 On the other hand, the findings of this meta-analysis need to be balanced against neuro-imaging evidence suggesting that even low levels of alcohol consumption are associated with poorer brain health,5 as well as dose-response relationships between alcohol consumption and other health outcomes such as cancer. For these reasons, advising those who currently abstain to initiate drinking is not recommended. Among current drinkers, alcohol consumption does not appear to be a consistent risk factor for dementia, although this relationship varied across continents and could not be examined among heavier drinkers.
- Harmonization of alcohol categories in the 15 cohorts.
- 11 of the 15 cohorts allowed separation of current abstainers into former drinkers and life-time abstainers.
- Cohorts from high-, low- and middle-income countries included.
- Effect of beverage type could not be investigated.
- Possible healthy survivor bias because small number of participants in the more extreme drinking categories.
- Limited ways to investigate the effect of frequency of alcohol consumption.
- Insufficient power to examine the relationship in South America and Africa.
- Mewton L, Visontay R, Hoy N, et al. The relationship between alcohol use and dementia in adults aged more than 60 years: a combined analysis of prospective, individual-participant data from 15 international studies. Addiction, 2022.
- Lundgaard I, Wang W, Eberhardt A, et al. Beneficial effects of low alcohol exposure, but adverse effects of high alcohol intake on glymphatic function. Sci Rep,
- Charlton AJ, May C, Luikinga SJ, et al. Chronic voluntary alcohol consumption causes persistent cognitive deficits and cortical cell loss in a rodent model. Sci Rep, 2019.
- Kimoto A, Izu H, Fu C, et al. Effects of low dose of ethanol on the senescence score, brain function and gene expression in senescence-accelerated mice 8 (SAMP8). Exp Ther Med,
- Topiwala A, Allan CL, Valkanova V, et al. Moderate alcohol consumption as risk factor for adverse brain outcomes and cognitive decline: longitudinal cohort study. BMJ,