Diet Quality and Dementia Risk in Older Adults With Alzheimer Pathology

Importance: Higher diet quality has been linked to reduced dementia incidence, but whether it buffers dementia onset in individuals with Alzheimer disease (AD) pathology or broader neurobiological risk is unclear. Objective: To explore the association of diet quality with dementia risk across biomarker levels of AD pathology (phosphorylated tau at threonine 217 [p-tau217]) and broader neurodegenerative and glial processes (neurofilament light chain [NFL], glial fibrillary acidic protein [GFAP]). Design, Setting, and Participants: This cohort study analyzed data from adults without dementia aged 60 years or older from the population-based Swedish National Study on Aging and Care in Kungsholmen, which enrolled participants between March 2001 and August 2004 and examined them up to 6 times until February 2016 to November 2019. Adherence to 3 dietary patterns was examined: the Alternate Mediterranean Diet (AMED), Alternative Healthy Eating Index (AHEI), and reversed Empirical Dietary Inflammatory Index (rEDII). Data were analyzed between September 2024 and August 2025 and reanalyzed in March and April 2026. Exposures: Baseline serum p-tau217, NFL, and GFAP concentrations and repeated adherence over 6 years to the AMED, AHEI, and rEDII dietary patterns. Main Outcomes and Measures: The primary outcome was all-cause dementia identified by clinical diagnosis, medical records, and death certificates. The secondary outcome was AD-related dementia. Dementia risk was analyzed using adjusted Cox regression models. Ten-year dementia probabilities and restricted mean time lost due to dementia were also estimated. Results: A total of 1865 participants were included (mean [SD] age at baseline, 70.5 [9.3] years; 1125 female [60.3%]). Over a mean follow-up of 8.4 years (range,