Independent and Joint Associations of Socioeconomic Status and Dietary Quality with Depressive and Anxiety Symptoms Among Chinese Older Adults: A Cross-Sectional Study of the Chinese Longitudinal Healthy Longevity Survey

Objectives: We assessed how socioeconomic status (SES) and diet quality, separately and jointly, related to depressive and anxiety symptoms in older Chinese adults. Methods: Data came from 9278 participants aged 65 years or older in the 2018 Chinese Longitudinal Healthy Longevity Survey. Education, main occupation before age 60, and annual household income were integrated into latent SES classes. Diet quality was represented by the Chinese-modified Mediterranean-DASH Intervention for Neurodegenerative Delay score (cMIND), Healthy Eating Index (HEI), Dietary Diversity Score (DDS), and Anti-Inflammatory Dietary Diversity Score (AIDDS). Depression and anxiety symptom status was determined from the 10-item Center for Epidemiologic Studies Depression Scale (CES-D-10) and 7-item Generalized Anxiety Disorder Scale (GAD-7). We used multivariable logistic models, joint-exposure models, restricted cubic splines, exploratory SES-by-diet interaction models, and multiple imputation for missing covariates. Results: Relative to high SES, low SES was associated with greater odds of depressive symptoms (OR = 1.50, 95% CI: 1.32–1.71) and anxiety symptoms (OR = 1.76, 95% CI: 1.43–2.16). All four dietary indices showed inverse associations with both outcomes. The largest joint estimates occurred for low SES plus low AIDDS (depressive symptoms: OR = 2.26, 95% CI: 1.94–2.64; anxiety symptoms: OR = 2.69, 95% CI: 2.12–3.40). No overall multiplicative interaction was found for dichotomized diet scores. For standardized continuous scores, nominal SES-by-diet interactions were observed for HEI, DDS, and AIDDS for depressive symptoms, but after Benjamini-Hochberg false-discovery-rate (FDR) correction only DDS and AIDDS remained below q < 0.05; no anxiety interaction survived correction. Conclusions: Socioeconomic disadvantage and poorer diet quality were each associated with greater symptom burden, while their co-occurrence identified the least favorable joint profile. Longitudinal and intervention studies are needed before dietary improvement can be interpreted as reducing SES-related mental-health inequalities.