Drinking one or two cocktails a day may protect against dementia, while having three or more could increase risk, new research suggests.

Investigators assessed dementia risk using changes in alcohol consumption over a 2-year period in nearly four million people in Korea. After about 7 years, dementia was 21% less likely in mild drinkers and 17% less likely in moderate drinkers. Heavy drinking was linked to an 8% increased risk.

Other studies of the relationship between alcohol and dementia have yielded mixed results, and this study does little to clear those murky waters. Nor do the results mean that drinking is recommended, the investigators note.

But the study does offer new information on how risk changes over time as people change their drinking habits, lead investigator Keun Hye Jeon, MD, assistant professor of family medicine at Cha Gumi Medical Center at Cha University, Gumi, Korea, told Medscape Medical News.

“Although numerous studies have shown a relationship between alcohol consumption and dementia, there is a paucity of understanding as to how the incidence of dementia changes with changes in drinking habits,” Jeon said.

“By measuring alcohol consumption at two time points, we were able to study the relationship between reducing, ceasing, maintaining, and increasing alcohol consumption and incident dementia,” he added.

The findings were published online February 6 in JAMA Network Open.

Tracking Drinking Habits

Researchers analyzed data from nearly four million individuals aged 40 years and older in the Korean National Health Insurance Service who completed questionnaires and underwent physical exams in 2009 and 2011.

Study participants completed questionnaires on their drinking habits and were assigned to one of five groups according to change in alcohol consumption during the study period. These groups consisted of sustained nondrinkers; those who stopped drinking (quitters); those who reduced their consumption of alcohol but did not stop drinking (reducers); those who maintained the same level of consumption (sustainers); and those who increased their level of consumption (increasers).

A standard drink in the US contains 14 g of alcohol. For this study, mild drinking was defined as <15 g/d, or one drink; moderate consumption as 15–29.9 g/d, or one to two drinks; and heavy drinking as ≥30 g/d, or three or more drinks.

At baseline, 54.8% of participants were nondrinkers, 26.7% were mild drinkers, 11.0% were moderate drinkers, and 7.5% were heavy drinkers.

From 2009 to 2011, 24.2% of mild drinkers, 8.4% of moderate drinkers, and 7.6% of heavy drinkers became quitters. In the same period, 13.9% of nondrinkers, 16.1% of mild drinkers, and 17.4% of moderate drinkers increased their drinking level.

After a mean follow-up of 6.3 years, 2.5% of participants were diagnosed with dementia, 2.0% with Alzheimer’s disease, and 0.3% with vascular dementia.

Unexpected Finding

Compared to consistently not drinking, mild and moderate alcohol consumption was associated with a 21% (aHR, 0.79; 95% CI, 0.77 – 0.81) and 17% (aHR, 0.83; 95% CI, 0.79 – 0.88) decreased risk for dementia, respectively.

Heavy drinking was linked to an 8% increased risk (aHR, 1.08; 95% CI, 1.03 – 1.12).

Similar associations were found between alcohol consumption and risk for Alzheimer’s disease and vascular dementia.

Reducing drinking habits from heavy to moderate led to a reduction in risk for dementia and Alzheimer’s, and increasing drinking levels led to an increase in risk for both conditions.

But when the researchers analyzed dementia risk for nondrinkers who began drinking at mild levels during the study period, they found something unexpected ― the risk in this group decreased by 7% for dementia (aHR, 0.93; 95% CI, 0.90 – 0.96) and by 8% for Alzheimer’s (aHR, 0.92; 95% CI, 0.89 – 0.95), compared to sustained mild drinkers.

“Our study showed that initiation of mild alcohol consumption leads to a reduced risk of all-cause dementia and Alzheimer’s disease, which has never been reported in previous studies,” Jeon said.

However, Jeon was quick to point out that this doesn’t mean that people who don’t drink should start.

Previous studies have shown that heavy alcohol use can triple an individual’s dementia risk, while other studies have shown that no amount of alcohol consumption is good for the brain.

“None of the existing health guidelines recommend starting alcohol drinking,” Jeon said. “Our findings regarding an initiation of mild alcohol consumption cannot be directly translated into clinical recommendations,” but the findings do warrant additional study, he added.

Risks Persist

Commenting on the findings for Medscape Medical News, Percy Griffin, PhD, director of scientific engagement for the Alzheimer’s Association in Chicago, agrees.

“While this study is interesting, and this topic deserves further study, no one should drink alcohol as a method of reducing risk of Alzheimer’s disease or other dementia based on this study,” said Griffin, who was not part of the study.

The exact tipping point in alcohol consumption that can lead to problems with cognition or increased dementia risk is unknown, Griffin said. Nor do researchers understand why mild drinking may have a protective effect.

“We do know, however, that excessive alcohol consumption has negative effects on heart health and general health, which can lead to problems with brain function,” he said. “Clinicians should have discussions with their patients around their alcohol consumption patterns and the risks associated with drinking in excess, including potential damage to their cognition.”

Funding for the study was not disclosed. Jeon and Griffin report no relevant financial relationships.

JAMA Netw Open. Published online February 6, 2023. Full text

Kelli Whitlock Burton is a reporter for Medscape Medical News covering psychiatry and neurology.

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