Cognitive trajectories and their relationships with education and diets among older adults: a network-based 10-year cohort study

Objectives Few studies have examined the underlying mechanisms of education, diets, and cognitive function in older adults. This study analyses the relationship between cognitive trajectories, education, and different dietary patterns in older adults from a network perspective, and further explores their longitudinal associations and mediation effects.Methods Data on cognitive trajectories were derived from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) between 2008 and 2018. Group-Based Trajectory Model (GBTM) was used to identify potential heterogeneity in the longitudinal changes in cognitive function. Multinomial logistic regression and network analysis were then applied to examine the relationships between different cognitive trajectories and years of education, food variety (FV), and plant-based dietary patterns. Cross-lagged panel model was used to examine the longitudinal associations between education, FV, and plant-based diet patterns. Furthermore, we constructed a mediation model based on categorical variables for cognitive trajectories to investigate the mediating effect of FV and plant-based diet index on education and cognitive.Results A total of 2,115 older adults were included in this study, revealing three distinct cognitive function trajectories. After controlling for potential confounders, education and dietary-related variables were associated with a cognitive stable decline trajectory (OR: 0.857/0.929/1.027) and a cognitive rapid decline trajectory (OR: 0.859/0.914, 95% CI: 0.775-0.882) compared to the cognitive stable trajectory. In the education, diet, and cognition network model, overall Plant-Based Diet Index (PDI) [expected influence (EI) = 1.82] and years of education (EI = 0.54) were the most central domains. There were longitudinal associations between education, FV, and plant-based dietary patterns, which were significant only in the slow decline group. FV acting as a mediator between education and cognitive trajectories.Conclusion Years of education are longitudinally associated with the diet of older adults in the slow cognitive decline group. Food diversity partially mediates the relationship between years of education and cognitive trajectories. Interventions targeting education and dietary behaviors may help alleviate cognitive decline in older adults.