Association between plant-based dietary patterns and cognitive function in middle-aged and older residents of China

Background Plant-based diets may protect against cognitive impairment; however, observational data have not been consistent. Objective This study aimed to evaluate the association between plant-based dietary patterns and cognitive function. Methods The study recruited 937 participants who were asked to complete food frequency questionnaires to assess the quality of their plant-based diets using the overall plant-based diet index (PDI), the healthful PDI (hPDI), and the unhealthful PDI (uPDI). Cognitive function evaluated using the Montreal Cognitive Assessment (MoCA) test. Logistic regression was used to explore the association between plant-based dietary patterns and the prevalence of mild cognitive impairment (MCI), while multiple linear regression was used to analyze the association between plant-based dietary patterns and cognitive scores. Results The prevalence of MCI was 26% among the 937 participants. There was a significant association between higher uPDI scores and higher odds of MCI, with Quintile 4 compared with Quintile 1 showing an odds ratio of 2.21 (95% confidence interval 1.35, 3.60). Higher uPDI scores were associated with a lower total MoCA score and poorer performance in various cognitive domains. There were no significant associations between the PDI, the hPDI, and cognitive function. Consuming whole grains, nuts, and eggs once a week or more were associated with a lower risk of MCI, whereas frequently consumption of pickled vegetables was associated with an increased risk of MCI. Conclusions Unhealthy plant-based diets were associated with cognitive impairment, while whole grains, nuts, and eggs may protect cognitive function; pickled vegetables are associated with cognitive impairment.