Drinking any amount of alcohol may increase the risk of developing dementia, according to the largest study to combine observational and genetic data.
The study, published in BMJ Evidence Based Medicine, found that even light drinking offers no protective benefit and that dementia risk rises with the amount of alcohol consumed.
In the past, some studies suggested that light drinking might protect brain health. However, those studies mostly looked at older adults and often didn’t separate lifelong non-drinkers from those who had stopped drinking due to health problems. This made it hard to be sure if alcohol itself was truly helpful.
To overcome these issues, researchers used data from two large groups: the US Million Veteran Program and the UK Biobank. These databases included health and genetic information from over 559,000 people.
Participants were monitored over time to see who developed dementia. The average follow-up was 4 years for the US group and 12 years for the UK group.
During the study, over 14,500 people developed dementia. At first, the observational data showed a U-shaped pattern: both heavy drinkers and non-drinkers had higher risks of dementia than light drinkers. But when researchers used genetic data, a clearer picture emerged.
They used a method called Mendelian randomisation, which uses genetic traits linked to alcohol use to understand lifetime risk. This approach avoids some of the biases in traditional studies.
It showed that dementia risk increased steadily as genetic risk for alcohol use rose. Even a small increase in alcohol—just 1 to 3 extra drinks per week—was linked to a 15% higher risk of dementia.
This new evidence challenges the belief that low levels of alcohol are good for brain health. The researchers also noticed that people who developed dementia often drank less in the years before their diagnosis, suggesting that early memory issues may have led them to cut back on drinking.
This could have confused earlier studies into thinking light drinking was protective.
While the strongest results were seen in people of European ancestry, the overall message is clear: alcohol use—at any level—may increase dementia risk. Reducing alcohol consumption might be an important step in preventing dementia.
The study is published in The BMJ.
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