Enhancing a plant-based diet can reduce the risk of multimorbidity in older adults

Multimorbidity has become widespread among older adults, and it is influenced by diet. However, research has yet to systematically explore the association of the overall plant-based diet index (PDI), healthful plant-based diet index (hPDI), and the unhealthful plant-based diet index (uPDI) on multimorbidity among older adults in China. In this research, we acquired data from 2018 cross-sectional survey of China Longitudinal Health and Longevity Survey (CLHLS). We use binary logistic regression to explore the association between PDI, hPDI, uPDI, and multimorbidity. Besides, restrictive cubic splines (RCS) were employed to explore whether the relationship between them is non-linear, and the effect of the interaction between different PDIs and some variables on multimorbidity was analyzed by subgroups. By imputing the missing values and excluding those with diabetes, we conducted two sensitivity analysis to prove the reliability of our research conclusions. This analysis encompassed 7,551 participants in total. After correcting for some confounding factors, we discovered that PDI (OR = 0.987, 95% CI: 0.978–0.997, P < 0.05) and hPDI (OR = 0.980, 95% CI: 0.970–0.991, P < 0.001) associated with multimorbidity negatively. In contrast, uPDI (OR = 1.016, 95% CI: 1.007–1.025, P < 0.001) associated with multimorbidity positively. RCS revealed a significant nonlinear relationship between PDI and multimorbidity, while there exists significant linear relationship between hPDI, uPDI, and multimorbidity. The results of interaction analysis indicate a significant interaction between place of residence and physical activity on the above results. We found similar results to the main findings of this study in two different sensitivity analyses. PDI and hPDI negatively associated with multimorbidity, while uPDI positively associated with multimorbidity. The conclusion of this research provides an inspiring dietary perspective for the future prevention of multimorbidity.