Associations of Distinct Dietary Indices with Global and Domain-Specific Cognition and Age-Related Heterogeneity in Older Chinese Adults

Background: Whether distinct dietary indices are similarly associated with cognitive domains and whether these associations vary by age remain unclear. We examined the Chinese MIND diet score (cMIND), dietary diversity score, and healthy plant-based diet index (HPDI) in relation to cognition among older Chinese adults. Methods: This cross-sectional study included 9615 adults aged 65 years or older from the 2021 Chinese Longitudinal Healthy Longevity Survey. Global cognition and four cognitive domains were assessed using the Chinese Mini-Mental State Examination. Sampling-weighted linear regression models evaluated each dietary index separately. Primary associations were estimated per 1-SD increment. Diet-by-age interactions were examined for global cognition, with complementary and sensitivity analyses. Results: All three dietary indices were positively associated with global cognition. Per 1-SD increment, adjusted β coefficients were 0.355 (95% CI 0.147 to 0.563) for cMIND, 0.342 (0.119 to 0.565) for dietary diversity, and 0.388 (0.132 to 0.643) for HPDI. All three indices were positively associated with attention, executive, and visuospatial function, while dietary diversity and HPDI were additionally associated with orientation. Formal comparisons showed no evidence that standardized associations differed across indices. Significant diet-by-age interactions were observed for all three indices, with more positive associations with global cognition at older ages (all interaction p < 0.001). Sensitivity analyses yielded broadly consistent findings. Conclusions: Higher cMIND, dietary diversity, and HPDI scores were associated with better global cognition, with statistical evidence of age-related heterogeneity in these cross-sectional associations across all three indices. These findings highlight the importance of considering dietary dimensions and age when characterizing diet–cognition relationships in older adults.