• Heavy drinking is associated with a wide range of illnesses, including Alzheimer’s disease, heart disease, and cancer.
• However, a new study suggests that mild or moderate alcohol intake could be associated with a reduction in a person’s risk of dementia, whereas heavy drinking is linked to an increased risk.
• A range of other health, social, and economic factors may explain the association, which remains controversial.
• Doctors do not recommend that people start drinking or increase their drinking, for whatever reason.

The evidence is clear that long-term, excessive alcohol consumption causes severe, life-threatening harm to health, including stroke, heart disease, liver disease, and cancer.

In the United States alone, around 140,000 people die every year as a result of excessive drinking, which shortens their lives by an average of 26 years.

So it comes as a surprise that several population-based studies have found an association between light or moderate alcohol consumption and a lower incidence of dementia.

There may be alternative explanations for the findings, however, and it is important to note that other studies have failed to find any protective effect.

A recent study that gave cognitive tests and brain scans to more than 25,000 people in the United Kingdom, for example, concluded that there is no safe level of alcohol consumption for brain health.

Cause and effect?

All the same, some observational studies do find a statistical link between light or moderate drinking and a lower risk of dementia. But with this type of research, it is difficult to establish whether alcohol has caused the reduction, or whether some other, related factor is responsible.

“There is a well-established link between heavy drinking and an increased risk of dementia,” Dr. Sara Imarisio, head of research at Alzheimer’s Research UK, told Medical News Today.

“But studies of alcohol intake can be challenging to carry out, and the evidence regarding the effect of moderate alcohol intake is much less clear,” she noted.

The latest results come from a study conducted in South Korea which found that long-term, light drinkers had a 21% lower risk of dementia compared with long-term non-drinkers. People who sustained a moderate alcohol intake had a 17% decreased risk.

Sustained heavy drinkers, by contrast, had an 8% increased risk of dementia compared with abstainers.

Perhaps the most striking finding was that non-drinkers who started to drink at low levels had a 7% reduced risk of dementia compared with those who continued to abstain.

The study results appear in JAMA Network Open.

Clear harms to health

Some research also suggests that moderate alcohol consumption can protect against cardiovascular disease, though this remains controversial.

The 2020-2025 Dietary Guidelines for Americans do not recommend that anyone who does not currently drink starts — for whatever reason.

This is because of the other clear harms to health from drinking alcohol, and the risk of dependence and addiction.

“[T]here are no convincing health grounds on which to drink alcohol,” said Dr. Sadie Boniface, head of research at the Institute of Alcohol Studies in London, U.K., and a visiting researcher at King’s College London.

“Even if there were protective effects of small amounts for some conditions, these are outweighed by other health risks,” she told MNT.

“For example, there’s concrete evidence of increased risks of alcohol-related cancers even for small amounts of alcohol,” she added.

How the study worked

The new study drew upon data from the Korean National Health Insurance Service, which provides a free health examination every two years to all insured individuals aged 40 years or older.

The exam comprises a questionnaire about participants’ medical history and lifestyle, such as drinking, smoking, and exercise.

The researchers, led by Dr. Keun Hye Jeon at Cha University in Gumi, Korea, looked at data from health exams in 2009 and 2011.

They excluded all participants with an existing diagnosis of dementia, cancer, or cardiovascular disease, and those who died within a year of their second examination.

After exclusions, there were almost 4 million participants with a mean age of 55 years.

The scientists divided participants into four categories according to their alcohol consumption:

• none — 0 grams (g) of alcohol per day
• mild — less than 15 g per day
• moderate — 15–29.9 g per day
• heavy — at least 30 g per day.

In the U.K., the National Health Service recommends that men and women drink on average no more than 2 units (16 g) of alcohol per day.

This is roughly equivalent to either a pint of regular-strength beer, two single shots of spirits, or a standard glass of wine.

In the U.S., the 2020-2025 Dietary Guidelines for Americans recommend that adults either abstain or limit their intake to two drinks or less a day for men, or one drink or less a day for women.

This study followed participants for a mean of 6.3 years and recorded diagnoses of different types of dementia, including Alzheimer’s disease and vascular dementia.

Unusually, by comparing participants’ alcohol consumption in 2009 and 2011, the researchers were able to estimate the risks associated with maintaining, reducing, or increasing alcohol intake. Most studies only record alcohol intake at one time point.

They adjusted their results to account for factors such as age, sex, exercise, income, and existing medical conditions.

Alternative explanations

Dr. Boniface pointed out that the moderate drinkers may have had other health behaviors or life circumstances that protected them against dementia, which were not fully accounted for in the study.

“In other areas, such as heart disease, apparent protective effects of small amounts of alcohol consumption have been explained by non-drinkers having pre-existing health conditions or in worse health on average,” she said.

“It’s too early to say if the same may be true for dementia,” she added.

Dr. Imarisio observed that non-drinkers are more likely to have a history of heavy alcohol use, which may have skewed the findings of the new study.

She noted that while the researchers looked at changes in drinking over time, the average age of participants was 55 years, and the study did not take into account past drinking behavior.

“It’s also the case that, while there are some proposed biological explanations for how moderate alcohol consumption could benefit the brain, it may be that moderate drinking reflects higher levels of social interaction, which has been linked with lower dementia risk.”

— Dr. Sara Imarisio

Other limitations

The study had several other limitations. For example, participants were part of a health-screening program and therefore may have been healthier and more concerned about leading a healthy lifestyle than the general population.

In addition, the results may not be widely applicable outside South Korea, due to differences in drinking cultures and genetic makeup, which can affect alcohol metabolism.

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