Alcohol use has been associated with an increased risk of cognitive decline and dementia . But new research from the Texas A&M University Naresh K. Vashisht College of Medicine at Texas A&M Health suggests the relationship between alcohol and Alzheimer's disease is more complicated than previously thought.
Instead of affecting all Alzheimer's-related brain changes in the same way, alcohol interacted differently with amyloid-beta-related and tau-related pathology in animal models, two key pathological processes involved in Alzheimer's disease.
The study was led by postdoctoral research associate Dr. Yufei Huang in the lab of Dr. Jun Wang , professor in the Department of Neuroscience and Experimental Therapeutics. The researchers focused on how alcohol affects brain circuits that are important for behavioral flexibility, or the ability to adjust behavior when situations change. This ability often becomes impaired in both addiction and Alzheimer's disease.
"We started thinking about whether the same circuits involved in flexibility and adaptation might also be important in Alzheimer's disease," Huang said.
The team studied a brain circuit called the corticostriatal circuit, which helps control decision-making and behavioral flexibility. When this circuit does not work properly, people may struggle to adapt to new information or changing environments.
To test the effects of alcohol, the researchers used animal models that represent different Alzheimer's-related pathological features. One model was based on amyloid-beta, a protein that forms plaques in the brain. The other was based on tau, a protein that forms tangles inside brain cells.
What they found surprised them.
Alcohol affected communication differently in the corticostriatal circuit, a major neural pathway involved with goal-directed behaviors. In animal models with amyloid-beta pathology, alcohol reduced communication in the circuit. In those with tau pathology, alcohol increased communication in the same circuit. In other words, the same exposure led to opposite effects depending on the type of Alzheimer's-related change present.
"This finding was a complete surprise to us," Huang said. "We expected alcohol to worsen both conditions in a similar way, but that was not what we saw."
The researchers explained that amyloid-beta and tau affect the brain differently. Amyloid-beta pathology is often associated with abnormal increases in neural activity, whereas tau pathology is frequently linked to decreased communication between brain cells. Based on these known differences, the team initially expected alcohol to push each model further in its existing pathological direction—increasing circuit communication in the amyloid-beta model and decreasing it in the tau model. Instead, alcohol produced the opposite pattern, reducing communication in the amyloid-beta model while increasing it in the tau model.
"The results were almost the opposite of what we expected," Huang said. "To us, this highlights an important principle in biology: Combining two risk factors does not always produce a simple additive effect."
The study adds to a growing understanding that Alzheimer's disease is not a single, uniform condition. Different people may have different combinations of disease stage, pathology, genetics and lifestyle factors, which could influence how the brain responds to outside factors such as alcohol.
"This is important because Alzheimer's disease is not a uniform condition," Huang said. "People may differ in disease stage, type of brain changes, genetics and lifestyle factors."
The study also highlights an unexpected link between Alzheimer's research and addiction science. The Wang lab has long studied how substances like alcohol affect brain circuits involved in learning and decision-making. Those studies showed that substance use can lead to long-term changes in brain flexibility, which is also affected early in Alzheimer's disease.
That overlap led researchers to ask whether alcohol might also influence Alzheimer's-related brain changes.
Beyond effects on brain signaling, the study also found that alcohol may interfere with immune cells in the brain, especially in the amyloid model. These immune cells, called microglia, help maintain brain health and respond to disease-related changes such as amyloid accumulation.
"Alcohol not only altered brain circuit function but also appeared to disrupt immune cell responses in the brain," Huang said. "This may be one way alcohol contributes to Alzheimer's-related brain dysfunction."
While the study was done in animal models, the researchers say the findings raise important questions for human health. Alcohol may not affect everyone with Alzheimer's risk in the same way. People who already have early disease-related brain changes, or who carry genetic risk factors, may respond differently to alcohol exposure.
The team hopes future studies will look at alcohol use in people alongside brain biomarkers such as amyloid, tau and inflammation markers. This could help clarify whether alcohol has different or stronger effects in people who are already in the early stages of Alzheimer's disease.
For now, the study adds to a growing understanding that brain health is shaped by a combination of biology, environment and lifestyle. Alcohol, rather than having a single effect on the brain, may interact with existing conditions in ways that are more complex than once thought.
Ultimately, the researchers say the goal is not only to understand Alzheimer's disease better, but also to better understand how everyday exposures may shape brain health over time.
This research was supported by funding from the National Institute on Alcohol Abuse and Alcoholism (NIAAA/NIH; U01AA025932, R01AA027768, and R01AA030293) and the Texas A&M University Division of Research Targeted Proposal Teams (TPT) funding program.
By Sunitha Konatham, Texas A&M Health
