Ultra-processed food consumption is emerging as a risk factor for various cardiometabolic diseases, however its association with dementia and Alzheimer's disease has rarely been explored.

We sought to examine whether ultra-processed food consumption is associated with risk of all-cause dementia and Alzheimer's disease among middle-age and older adults.

A prospective cohort study.

The Framingham Heart Study, a single-site, community-based cohort study.

Offspring cohort participants who attended examination cycles 5 (1991-1995) and 7 (1998-2001) at age ≥60 years and who were dementia-free at baseline.

Nutritional information was retrieved from food frequency questionnaires, and ultra-processed food was categorized based on the NOVA system. Participants were followed-up for all-cause dementia and Alzheimer's disease. Cox regression models were used to estimate hazard ratios (HRs) and 95 % confidence intervals (CIs) adjusting for potential confounders.

The study sample included 1,375 participants free of dementia and stroke at baseline (mean age 68 ± 6y, 54 % females). During a mean follow-up of 12.7 ± 6.0 years, 224 and 172 individuals were diagnosed with all-cause dementia and Alzheimer's disease, respectively. An interaction of ultra-processed food consumption with age was observed with regard to dementia and Alzheimer's disease (p for interaction = 0.02 and 0.007, respectively). Therefore, all analyses were stratified by the median age of 68 years. Among participants who were <68 years of age at baseline, each serving per day of ultra-processed food was associated with 13 % increased risk for Alzheimer's disease (HR = 1.13, 95 % CI:1.03-1.25), and consumption of ≥10 servings/day vs. <10 servings/day of ultra-processed food was associated with a 2.7-fold increase in Alzheimer's disease risk (HR = 2.71, 95 % CI:1.18-6.24), after adjustment for age, sex, education, total energy, metabolic factors and diet quality. The associations with all-cause dementia were less robust, and no significant findings were observed when age at baseline was 68 years or above.

Our findings suggest that consumption of ultra-processed food in middle-age may be linked with an increased risk for Alzheimer's disease. Future clinical studies are warranted to assess whether reduction of ultra-processed food consumption improves brain health.