Despite a few minor upsides, we’ve known for a while that alcohol is bad for you — and especially for your brain. Now, a new nationwide study found that heavy use of alcohol is the most significant promoter of dementia, and even doctors are underestimating the negative effect of those extra drinks.

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Researchers in France analyzed the effect of alcohol use on dementia. They analyzed over one million people diagnosed with dementia, trying to see what the underlying causes were. They found that on average, heavy alcohol consumption shortens life expectancy by more than 20 years and dementia is one of the main causes.

Out of all the preventable factors, alcohol reigned supreme. Overall, people who were chronic drinkers were three times more likely to suffer from dementia than others. Strikingly, 57% of all early-onset dementia cases were associated with heavy chronic drinking. There was also an important gender gap: while overall, most dementia patients were women, 64.9% of early-onset patients were men.

[alert style=”alert-success” close=”false”]The World Health Organization defines chronic heavy drinking as consuming more than 60 grams pure alcohol on average per day for men and 40 grams for women. For reference, a beer contains around 20-25 grams of pure alcohol, as does a glass of wine.[/alert]

“The findings indicate that heavy drinking and alcohol use disorders are the most important risk factors for dementia, and especially important for those types of dementia which start before age 65, and which lead to premature deaths,” says study co-author and Director of the CAMH Institute for Mental Health Policy Research Dr. Jürgen Rehm. “Alcohol-induced brain damage and dementia are preventable, and known-effective preventive and policy measures can make a dent into premature dementia deaths.”

However, this was just an observational study, and no causation was established. This means that there are other factors associated with drinking that influence the dementia rate. For instance, heavy drinkers also tend to be smokers, which also has an important effect on dementia — and it’s not just dementia.

Heavy drinkers were also more likely to be depressed and had an increased risk of high blood pressure, diabetes, stroke and heart failure, which can also influence dementia.

But the bottom line is clear as day: alcohol is bad for you. Low consumption of alcohol is still dangerous, but heavy consumption can be extremely damaging. The researchers also suggest a list of measures which can help reduce consumption, including increased alcohol taxes and advertising bans.

“If all these measures are implemented widely, they could not only reduce dementia incidence or delay dementia onset, but also reduce all alcohol-attributable morbidity and mortality,” they wrote.

Dementia is a prevalent condition, affecting 5–7% of people aged 60 years and older, and a leading cause of disability in people aged 60 years and older globally, researchers write.

Journal Reference: Schwarzinger et al. “Contribution of alcohol use disorders to the burden of dementia in France 2008–13: a nationwide retrospective cohort study”. Lancet, DOI: https://doi.org/10.1016/S2468-2667(18)30022-7