Dietary Patterns and Cognitive Decline in Older Adults: Findings from the Western Australia Memory Study

Background: Preventive strategies, including adherence to specific dietary patterns, have received increasing attention as approaches to reduce cognitive decline and dementia risk. However, findings remain inconsistent, partly due to differences in dietary assessment methods, cognitive outcomes, and THE consideration of genetic susceptibility factors such as apolipoprotein E (APOE) genotype. Methods: This study examined associations between dietary patterns and longitudinal cognitive change in 185 older adults without dementia from the Western Australia Memory Study. Participants completed a food frequency questionnaire at baseline and underwent comprehensive neuropsychological assessments at baseline and up to five follow-up visits at 18-month intervals. Composite scores were generated for six cognitive domains and the Preclinical Alzheimer’s Cognitive Composite (PACC). Results: Western and Prudent dietary pattern scores were analysed using linear mixed-effects models stratified by APOE ε4 carrier status. Among APOE ε4 carriers, greater adherence to a Western dietary pattern was associated with a faster decline in attention (p = 0.016), whereas no significant associations were observed for the Prudent dietary pattern or among APOE ε4 non-carriers. This association was attenuated after excluding participants with possible baseline cognitive impairment (MoCA < 23). Conclusion: These findings suggest that adherence to a Western dietary pattern may accelerate cognitive decline in individuals genetically at risk for Alzheimer’s disease, highlighting the importance of considering gene–diet interactions when developing dietary strategies for dementia prevention.