Unprocessed vs. ultra-processed food intake and major neurocognitive disorder (MNCD) among older adults: insights from the second phase of the Birjand longitudinal aging study

Ultra-processed foods (UPFs) are industrially formulated products containing various additives, and their potential relationship with cognitive health has raised increasing concern, particularly among older adults. This study examined the association between dietary processing levels and major neurocognitive disorder (MNCD) among older adults. This cross-sectional study utilized data from the second phase of the Birjand Longitudinal Aging Study (BLAS), conducted between November 2021 and May 2022. Dietary intake was assessed using a validated semi-quantitative Food Frequency Questionnaire (FFQ) and categorized according to the NOVA classification. Cognitive status was assessed by a neurologist using DSM-5 criteria, neuropsychological tests, interviews, and magnetic resonance imaging (MRI) when indicated. Logistic regression analyses were performed. A total of 1,017 older adults were included, with a mean age of 72.4 years, and 50.2% were female; 13.8% had MNCD. Participants with MNCD were more often female, had lower educational attainment, and consumed fewer unprocessed foods. Higher intake of unprocessed foods was consistently associated with lower odds of MNCD across the sequential models, including the principal analytical model (OR: 0.55; 95% CI: 0.32–0.92). No statistically conclusive evidence of an association was observed between processed or ultra-processed food intake and MNCD. Higher unprocessed food intake was associated with lower odds of MNCD in older adults, although associations with ultra-processed foods remained inconclusive. Given that the NOVA classification does not fully capture dietary quality, longitudinal research is essential to establish the causal relationships between food processing, nutrient composition, and cognitive health.