Unhealthy Western diet linked to faster cognitive decline in people with genetic risk of Alzheimer's

Partial explanation for Trump's behavior issues

By Murdoch University

Edited by Sadie Harley, reviewed by Robert Egan

An unhealthy Western-style diet was associated with faster cognitive decline in people with a genetic risk of Alzheimer's disease, according to new research led by Murdoch University and Alzheimer's Research Australia. 

The study, Dietary patterns and cognitive decline in older adults: Findings from the Western Australia Memory Study, appears in the journal Nutrients.

As the world grapples with the growing public health challenge of dementia, there has been increasing academic interest in identifying lifestyle factors that may help maintain people's brain health as they age.

"Diet is particularly interesting because it is often easily modifiable, but people may not respond to dietary patterns in the same way," said lead author Dr. Carolina Blagojevic Castro, from Murdoch University's Center for Healthy Aging.

"In this study we investigated whether the types of food people regularly eat are associated with how their thinking abilities change as they get older," Blagojevic Castro said.

Tracking diet, genes and cognition

Using data from the Western Australia Memory Study (WAMS), the research team followed 185 older adults from Perth for more than seven years and examined whether unhealthy and healthier dietary patterns were associated with changes in different areas of their cognition, while also considering individuals' genetic risk for Alzheimer's disease.

The team grouped the participants' diets into two main groups: a Western diet (unhealthy diet), consisting of foods such as red and processed meat, chips, pizza, sweets, refined grains and beer, and a prudent diet (healthy diet), consisting of things like fruit, vegetables, leafy greens, garlic and whole grains.

None of the participants had diagnosed dementia when they entered the study, but they were tested for genetic susceptibility factors such as the apolipoprotein E (APOE) variant, the strongest common genetic risk factor for Alzheimer's disease.

Throughout the study, participants completed a series of cognitive tests to assess their attention, memory, executive function, language, recognition memory and general cognitive ability.

The effect appeared in carriers

"Our main finding was that among people carrying the APOE ε4 allele, greater adherence to a Western dietary pattern was associated with a faster decline in attention over time," Blagojevic Castro said.

"One of the most interesting findings was that the association with cognitive decline was not seen across the whole group but emerged specifically among APOE ε4 carriers."

"We did not find significant associations between the healthier prudent dietary pattern and cognitive decline, or between the Western dietary pattern and cognitive decline among people who did not carry APOE ε4."

Blagojevic Castro said the findings reinforced growing evidence that the relationship between diet and brain health was complex and not the same for everyone.

"What we eat may be one part of a much larger picture of healthy brain aging," she said.

Caution before dietary advice

"Our findings highlight why research into individual differences is important—approaches to protecting brain health may ultimately need to consider both lifestyle and biological factors rather than assuming that one approach will work equally well for everyone."

"However, our study is observational, so further research is needed before these findings can be translated into specific dietary recommendations based on genetic risk."

Publication details

Carolina Blagojevic Castro et al, Dietary Patterns and Cognitive Decline in Older Adults: Findings from the Western Australia Memory Study, Nutrients (2026). DOI: 10.3390/nu18162592