Associations between plant-based dietary pattern trajectories and depression and life satisfaction in older adults: insights from the 2008–2018 Chinese Longitudinal Healthy Longevity Survey (CLHLS)

Plant-based diets may improve mental health among older adults by alleviating depression and improving life satisfaction. This study aimed to explore the associations between plant-based dietary pattern trajectories (PDPT), depression and life satisfaction in Chinese older adults. Data of participants from the 2008-2018 Chinese Longitudinal Healthy Longevity Survey were analysed. We utilised group-based trajectory modelling to identify the PDPT. Logistic and linear regression models were used to analyse the associations between PDPT, depression and life satisfaction. In total, 1835 participants were divided into three groups based on plant-based dietary index (PDI), healthy plant-based dietary index (HPDI) or unhealthy plant-based dietary index (UPDI) trajectories, respectively, and the PDPT were maintained at stable levels. PDI trajectory was not significantly associated with depression or life satisfaction. HPDI trajectory had no significant association with depression. However, compared with low HPDI trajectory, participants in the high (<i>β</i> = 0·185, 95 % CI: 0·032, 0·337) HPDI trajectories had higher life satisfaction. Compared with the low UPDI trajectory, participants in the high UPDI trajectory groups were associated with a higher risk of depression (OR = 1·793, 95 % CI: 1·124, 2·861). Further, the medium (<i>β</i> = -0·145, 95 % CI: -0·273, -0·018) and high (<i>β</i> = -0·335, 95 % CI: -0·478, -0·191) UPDI trajectory were associated with poor life satisfaction. Dietary interventions should be prioritised to address the persistent unhealthy dietary habits among Chinese older adults, with particular emphasis on reducing UPDI to enhance mental health by promoting intake of healthy plant-based and animal-based foods while avoiding unhealthy plant-based foods.