Dietary diversity trajectories and depression symptoms among rural older adults: a latent class growth analysis and network analysis based on the China longitudinal health and longevity study

Depression imposes a significant burden on older adults, particularly among rural populations. Research indicates an association between dietary diversity and depressive symptoms, yet the relationship between dietary diversity trajectories and depressive symptoms remains unclear. This study aims to examine the relationship between dietary diversity and depressive symptoms from a dynamic perspective. Data from the China Longitudinal Health and Longevity Survey (CLHLS) covering 2011–2018 were used, including 899 rural residents aged ≥60 years. Dietary diversity and depressive symptoms were assessed using the Food Frequency Questionnaire and the Centre for Epidemiologic Studies Depression Scale (CESD-10). Latent class growth analysis identified dietary diversity trajectories among rural older adults. Logistic regression models examined the association between different trajectories and depressive symptoms. Finally, network analysis was used to calculate the expected influence of depressive symptoms across different dietary diversity trajectories, identifying central symptoms. Two dietary diversity trajectories were identified: a high and gradually increasing trajectory and a persistently low trajectory. After adjusting for covariates, the persistently low dietary diversity trajectory group had a higher risk of depression than the high and gradually increasing trajectory group (OR = 0.54, 95% CI: 0.396–0.736). The network structures of depressive symptoms differed significantly in overall intensity between the two trajectories (S = 0.98, p = 0.002), while no significant difference was observed in network structure (M = 0.13, p = 0.814). Core symptoms differed partially: CESD-3 ("Feeling depressed") and CESD-9 ("inability to get going") in one group, and CESD-3 ("Feeling depressed") and CESD-4 ("Everything was an effort") in the other. Maintaining high and gradually increasing dietary diversity reduces the risk of depression among rural older adults in China. Dietary diversity-related educational activities can raise awareness of dietary importance among this population. Tailoring interventions to the core symptoms of different dietary diversity groups will ultimately lower depression incidence and promote healthy ageing.