Red wine being poured into the glass at the table. Photo / Getty Images
Findings challenge the idea that moderate drinking could benefit brain health.
Drinking any amount of alcohol may increase the risk of developing dementia, the largest study of its kind has suggested.
The findings challenge the idea that light drinking could benefit brain health, researchers have said.
They also suggest that cutting down alcohol consumption across the population could “play a significant role in dementia prevention”.
The study, led by experts at the University of Oxford, Yale University, and the University of Cambridge, looked at data from 559,559 people in the UK Biobank and the US Million Veteran Programme.
During the follow-up period, some 14,540 people developed dementia.
The observational results showed a U-shaped pattern: people who did not drink at all, and those who drank heavily had higher dementia risk than light drinkers.
However, researchers said this was likely to be caused by “reverse causation”, where early dementia symptoms lead people to cut back or stop drinking.
This means people who appear to be “healthy non-drinkers” in observational studies may have already been in cognitive decline, skewing the data.
To test this, the researchers used Mendelian randomisation, a genetic method that avoids many of the pitfalls of traditional observational studies.
Researchers analysed genetic variants linked to alcohol use, drawing on data from 2.4 million people across multiple genome-wide association studies. These variants indicate a person’s lifetime tendency to drink alcohol, regardless of their current habits.
Three different genetic markers were analysed: one linked to weekly drinking volume, one to risky drinking behaviour, and one to alcohol dependence.
In all three cases, higher genetic predisposition to drinking was associated with greater dementia risk. The more genetically predicted alcohol consumption increased, the higher the likelihood of dementia.
For example, just one to three additional drinks per week led to a 15% higher risk of dementia.
These genetic analyses showed a linear relationship between alcohol and dementia. There was no U-shaped curve and no protective effect of light drinking.
This challenges the widely held belief that small amounts of alcohol, such as a daily glass of wine, could protect the brain.
Dr Anya Topiwala, the senior clinical researcher at Oxford Population Health and consultant psychiatrist, 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 Joel Gelernter, a professor at Yale University and senior author of the study, said the findings, published in BMJ Evidence Based Medicine, not only add to the understanding of the relationship between alcohol and dementia but also have “clinical implications”.
He added: “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.”
According to the Alzheimer’s Society, about 982,000 people in the UK have dementia.
By 2040, about 1.4 million people in the UK could be living with the condition.
Dr Stephen Burgess, a 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 a higher risk of dementia.”
The genetic analysis helps researchers identify whether alcohol causes dementia, rather than simply being associated with it. However, other experts highlighted limitations in the research.
Prof Sir David Spiegelhalter, emeritus professor of statistics at the University of Cambridge, said the genetic predictions “rely on many unverifiable assumptions” and were not based on actual alcohol consumption.
Prof Tara Spires-Jones, director of the Centre for Discovery Brain Sciences at the University of Edinburgh, group leader in the UK Dementia Research Institute, and past president of the British Neuroscience Association, said: “Authors rightly acknowledge several important limitations of the study.
“Self-reported alcohol use may not be accurate, particularly if people have memory problems in early stages of dementia, and the genetic markers used as predictors of both alcohol intake and dementia are not perfect.
“Neither part of the study can conclusively prove that alcohol use directly causes dementia, but this adds to a large amount of similar data showing associations between alcohol intake and increased dementia risk, and fundamental neuroscience work has shown that alcohol is directly toxic to neurons in the brain.”