Scientifically reviewed by Sharyn Rossi, PhD
If you enjoy a glass of wine (or two) at the end of the day, you may want to think again. Even moderate alcohol use—two drinks or less in a day for men and one drink or less in a day for women—can affect the brain and may accelerate Alzheimer’s disease progression, according to research funded by BrightFocus Foundation’s Alzheimer’s Disease Research program.
The study found that drinking alcohol accelerated the loss of brain cells and increased the number of amyloid plaques in brains with Alzheimer’s disease pathology. In people with Alzheimer’s disease, these protein plaques clump together and collect between neurons to disrupt brain function. The team concluded that alcohol consumption may be a modifiable risk factor—one that you can take measures to change—for Alzheimer’s disease and dementia.
The research team included Alzheimer’s Disease Research grantee Shannon L. Macauley, PhD, assistant professor of gerontology and geriatric medicine at Wake Forest School of Medicine.
Sorting through the evidence
The relationship between alcohol and Alzheimer’s disease is complicated. Some studies have found that small amounts of alcohol may actually protect against cognitive decline. But there is significant evidence that people who abuse alcohol have an increased risk of dementia.
To explore this knowledge gap, Dr. Macauley and her team studied the impact of chronic, moderate alcohol use.
“There’s a lot of conflicting evidence as to whether alcohol is helpful or harmful,” she explained. “We were trying to get a more complete understanding of how alcohol affects Alzheimer’s disease.”
Ethanol is the form of alcohol found in drinks such as beer, wine, and liquor. The research team conducted their study to determine how chronic ethanol use altered the behavioral and metabolic changes associated with dementia in mice.
They used a 10-week chronic drinking approach where mice were given the choice to drink water or ethanol, similar to the way people choose to drink, to look at how voluntary, moderate drinking altered brain function and whether it impacted the pathways associated with Alzheimer’s disease.
The researchers found that alcohol increased brain atrophy in Alzheimer’s disease-brains and caused an increased number of amyloid plaques including a greater number of smaller plaques, which over time can proliferate. Their findings suggest that brain stimulation caused by ethanol may play a role in Alzheimer’s progression by accelerating the loss of neurons and the connections between them.
Alzheimer’s disease: a growing concern
Alzheimer's disease, the most common form of dementia, is the only leading cause of death that is still on the rise. Contrary to what many still believe, it is not a normal part of aging.
Age is the greatest risk factor; 33% of people age 85 and older have Alzheimer's dementia. By 2050, the number of Americans age 65 and older with Alzheimer's and related dementias is estimated to be as high as 16 million.
The disease has the potential to cripple the U.S. healthcare system, unless researchers can find new ways to prevent or cure it. Identifying risk factors that may contribute to Alzheimer’s disease, and making lifestyle changes to avoid them, is becoming more and more critical as the population ages.
The next research steps
On the heels of their current research findings, Dr. Macauley and her team are working on new studies, including doubling the length of their original study to examine longer-term effects of moderate alcohol use. One area of concentration is the biological ways in which alcohol affects brain changes that may accelerate Alzheimer’s disease.
“If you have a healthy brain that can clear ethanol and your consumption is minimal, maybe drinking has little impact,” she said. “As we hit middle age, however, our metabolism changes, and alcohol may be something to avoid.”
Researchers also don’t fully understand how co-occurring conditions (comorbidities) like type 2 diabetes and cardiovascular disease may factor in. “We saw a lot of vascular changes, so maybe alcohol has more of an effect on the circulatory system in the brain,” Dr. Macauley said. “We’re trying to tease out if that’s what we’re seeing.”
For now, until researchers learn more about individual risk—such as how many years someone drinks, how much they drink, their genetic background, and gender—there are no specific guidelines to follow. But, Dr. Macauley points out, “our study found that even a very modest dose of alcohol caused some long-term changes in the brain.”
The preclinical study was published in the February 2023 issue of the scientific journal Neurobiology of Disease.
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