Any amount of alcohol consumption may increase risk of dementia, according to the most comprehensive study of alcohol consumption and dementia risk to date.
Led by the University of Oxford, Yale University, and the University of Cambridge, the research challenges previous suggestions that light-to-moderate drinking may have a protective effect against dementia. The study is published in BMJ Evidence-Based Medicine .
Alcohol consumption is widespread and is linked with an increased risk of many diseases. Heavy drinking has previously been linked to higher risk of dementia. The connection between moderate levels of drinking and higher risk of dementia was uncertain with some studies suggesting that moderate drinking may even reduce dementia risk. However, recent studies involving brain scans have shown that drinking alcohol even at low levels may increase the risk of dementia.
This study combined observational data from more than half a million participants in two large and diverse population studies: the US Million Veteran Program and UK Biobank to assess whether self-reported alcohol use was linked with risk of developing a broad range of types of dementia.
The researchers also investigated links between genetically-predicted likelihood of drinking alcohol and alcohol use disorder for more than 2.4 million participants in 45 individual studies. This approach helped the researchers overcome some of the difficulties in distinguishing correlation from causation.
Key findings:
- Observational analyses seemed to support previous findings that current low and moderate drinking is associated with lower risk of dementia when compared with non-drinking and heavy drinking; however, some current non-drinkers were previously heavy drinkers, which could account for their increased dementia risk compared to consistently low drinkers;
- Genetic analyses, however, revealed a continuously increasing trend of higher dementia risk with greater alcohol intakes, suggesting that any level of alcohol consumption increases the risk of dementia, with no evidence that drinking alcohol may have a protective effect;
- A doubled increase in a person's genetically-predicted risk of alcohol use disorder was associated with a 16% higher risk of dementia, while a three times higher increase in number of alcoholic drinks per week increased the risk of dementia risk by 15%;
- The study also showed that people who later developed dementia reduced their alcohol intake before diagnosis, another explanation for prior findings of protective effects of alcohol, rather than true benefit.
Dr Anya Topiwala , Senior Clinical Researcher at Oxford Population Health , Consultant Psychiatrist, and lead author of the study, said 'Our findings challenge the common belief that low levels of alcohol are beneficial for brain health. Genetic evidence offers no support for a protective effect - in fact, it suggests the opposite. Even light or moderate drinking may increase the risk of dementia, indicating that reducing alcohol consumption across the population could play a significant role in dementia prevention.'
Dr Stephen Burgess, Statistician at the University of Cambridge, said 'The random nature of genetic inheritance allows us to compare groups with higher and lower levels of alcohol drinking in a way that allows us to make conclusions that untangle the confusion between correlation and causation. Our findings do not only hold for those who have a particular genetic predisposition, but for anyone who chooses to drink, our study suggests that greater alcohol consumption leads to higher risk of dementia.'
Dr Joel Gelernter, Professor at Yale University and senior author of the study, said 'These results, which add to our understanding of the relationship between alcohol and dementia, have clinical implications - there was a time when medical knowledge seemed to support that light drinking would be beneficial to brain health, and this work adds to the evidence that this is not correct'.
This study adds to growing evidence that alcohol use, even at moderate levels, may have no safe threshold when it comes to brain health, reinforcing the case for preventive strategies that reduce alcohol consumption in the general population.
The study,' Alcohol use and risk of dementia in diverse populations: evidence from cohort, case-control and Mendelian randomisation approaches ', is published in BMJ Evidence-Based Medicine .
