Diet’s link to dementia differed by gene variant in older adults
In one genetic group, each extra diet-score point was linked to lower relative Alzheimer’s dementia risk over time (hazard ratio 0.82).
An observational cohort study followed 745 older adults, whose mean age was 80.0 years, in the Rush Memory and Aging Project. Researchers used a food questionnaire to score adherence to a Mediterranean-style diet intended to delay cognitive decline, from 0 to 15. They repeatedly assessed thinking skills and diagnosed dementia through clinical examinations.
The diet’s associations with Alzheimer’s dementia, dementia of any cause and cognitive decline differed by variants of COMT, a gene involved in breaking down certain brain chemicals. Higher diet scores were associated with greater cognitive benefits among people with two copies of a variant linked to lower COMT activity. In this group, the Alzheimer’s dementia hazard ratio—a measure of relative risk over time—was 0.82 per diet-score point. The other two genetic groups showed no clear association with Alzheimer’s dementia.
Why it matters
For efforts to preserve thinking skills in later life, the study raises the question of whether dietary advice should account for genetic differences.
Caveats
This observational study cannot establish that diet caused the differences in cognitive decline or dementia. The findings in older adults do not establish whether the same links occur in younger people.
The paper
Northwestern University; Rush Alzheimer’s Disease Center
Nutrients, 30 Sep 2026, Open access
