Many people believe that having a small amount of alcohol now and then might be good for the brain.
But a large new study suggests that even light drinking may increase the risk of dementia. In fact, the more alcohol people consume, the higher their risk appears to be.
The study, published in BMJ Evidence-Based Medicine, is the largest of its kind.
It combined two types of data: regular health observations and genetic information.
By looking at both, researchers were able to get a clearer picture of how alcohol affects the brain over time.
Earlier studies often showed a U-shaped pattern, suggesting that people who drank lightly had a lower risk of dementia than those who drank heavily or not at all.
But many of those studies only included older adults and didn’t separate people who had never drunk alcohol from those who had stopped for health reasons. This made it difficult to know what was really causing the changes in dementia risk.
To solve this, researchers used data from two massive health databases: the US Million Veteran Program and the UK Biobank.
Together, they included over half a million adults aged 56 to 72 who were free of dementia when the study began. Most of the participants—over 90%—reported drinking alcohol.
Over the next several years, researchers tracked who developed dementia and how much they drank. Around 14,500 people developed dementia during the study, and nearly 48,000 died.
People who drank heavily (40 or more drinks a week) and those who were alcohol dependent had about a 41% to 51% higher risk of dementia compared to light drinkers (fewer than seven drinks per week).
Interestingly, even people who didn’t drink at all had a slightly higher risk, which may be due to past health problems or early signs of dementia that led them to stop drinking.
To better understand the link between alcohol and dementia, the researchers also used a method called Mendelian randomization. This approach uses genetic data to estimate the lifetime effect of alcohol on dementia risk. They analyzed data from over 2.4 million people from previous genetic studies.
The genetic data showed a clear pattern: the more genes a person had that were linked to drinking, the higher their risk of developing dementia. For example, having genes linked to drinking one to three extra drinks a week was tied to a 15% higher risk of dementia. A strong genetic risk for alcohol dependence was linked to a 16% higher risk.
Importantly, this method found no sign that light drinking protects the brain. Instead, the risk of dementia steadily rose with more alcohol use. The researchers also noticed that people who developed dementia often drank less in the years leading up to their diagnosis.
This suggests that early memory problems might cause people to cut back on drinking, which could explain why earlier studies made light drinking look protective.
The study had some limitations. Most of the data came from people of European descent, so the findings might not apply to everyone. Also, genetic studies make certain assumptions that can’t always be proven. Still, the researchers believe their findings are strong enough to question the idea that a little alcohol is good for brain health.
They concluded that all levels of alcohol consumption likely raise the risk of dementia and that cutting back on drinking might help protect the brain.
The study is published in BMJ Evidence-Based Medicine.
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