Some studies have suggested that drinking alcohol in moderation lowers the risk of dementia, but the evidence may have been prone to certain biases. A new study follows more than 9,000 people over a 23-year period to draw robust conclusions on the link between alcohol consumption and dementia risk.

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While moderate drinking may be good for brain health, excessive alcohol consumption may put seniors at risk of dementia.

As the world population grows increasingly older, more and more people are at risk of developing dementia.

In fact, according to recent estimates, almost 50 million people worldwide are currently living with dementia, and this number is expected to double every 2 decades, reaching over 130 million by 2050.

In the United States, 5.7 million Americans are thought to have Alzheimer’s disease, and experts estimate that by 2050, this number will have reached 14 million.

In this context, research into the risk factors for developing dementia is vital. From a lack of physical activity to high blood pressure and even sleep troubles, the range of dementia risk factors that are being uncovered by the latest studies is varied.

But what about alcohol? Some studies have suggested that moderate alcohol intake may have protective effects on the brain, whereas excessive consumption is thought to raise the risk of dementia.

However, most of these studies have looked only at alcohol intake in later life, without accounting for the lifetime consumption. Such an approach may have skewed the results.

So, a team of researchers from Inserm — the French National Institute of Health and Medical Research in Paris, France — in collaboration with scientists from University College London (UCL) in the United Kingdom set out to rectify this by looking at patterns of alcohol consumption from mid-life into old age.

The first author of the paper is Séverine Sabia, a researcher affiliated with both of the above institutions, and the findings were published in The BMJ.

Sabia and colleagues examined 9,087 study participants who were aged between 35 and 55 at the beginning of the study.

The team assessed their alcohol consumption and potential dependence regularly using standard questionnaires and by looking at alcohol-related hospital admissions.

The researchers also examined hospital records for cases of dementia, as well as for any diagnoses of cardiometabolic conditions, such as heart disease or diabetes.

For the purposes of the study, anything over 14 standard U.K. alcohol units per week counted as heavy drinking. In the U.K., a standard glass of wine counts as 1 unit of alcohol, and 14 weekly units is the maximum threshold for what is considered harmful drinking.

In the U.S., the Dietary Guidelines for Americans recommend that men should not drink more than two drinks per day and women should not exceed one drink per day.

The average follow-up period for the study was 23 years. During this time, 397 people developed dementia. Sabia and team accounted for various sociodemographic factors that may have influenced the results.

The findings revealed that both abstaining from alcohol in midlife and drinking heavily raised the risk of dementia when compared with light-to-moderate drinking.

More specifically, alcohol-related hospital admissions raised the risk of dementia by fourfold.

Long-term abstinence, on the other hand, also correlated with a higher risk of dementia, due to a higher incidence of cardiometabolic conditions.

Sabia and colleagues comment on the findings, saying that they “strengthen the evidence that excessive alcohol consumption is a risk factor for dementia.”

The results also “encourage use of lower thresholds of alcohol consumption in guidelines to promote cognitive health at older ages,” write the authors.

However, the researchers warn, the results of this study “should not motivate people who do not drink to start drinking given the known detrimental effects of alcohol consumption for mortality, neuropsychiatric disorders, cirrhosis of the liver, and cancer.”

In an editorial comment, Sevil Yasar, from the Johns Hopkins School of Medicine in Baltimore, MD, also weighs in on the findings.

[A]lcohol consumption of 1-14 units/week may benefit brain health; however, alcohol choices must take into account all associated risks, including liver disease and cancer.”

Sevil Yasar