Effects of particulate matter exposures on depressive symptom trajectories: Evidence from a national longitudinal survey in China

Aim This study aimed to assess the associations between particulate matter (PM) exposures and depressive symptom trajectories, as well as the potential contributing role of loneliness in these associations. Methods The analysis included 11,758 participants (≥45 years), with depressive symptoms and covariate data from the China Health and Retirement Longitudinal Study (2011–2020) and PM data from the ChinaHighAirPollutants dataset. Depressive symptom trajectories were identified using group‐based trajectory modeling. Individual and combined effects of PM on depressive symptom trajectories were assessed using multivariable logistic regression and weighted quantile sum (WQS) regression, with results reported as odds ratio (OR) and 95% confidence interval (CI). A serial multiple mediator model was used to evaluate the contributing role of loneliness. Results Five depressive symptom trajectories were identified: stable‐low, stable‐moderate, stable‐high, decreasing, and increasing. PM exposures were positively associated with more severe depressive symptom trajectory groups (stable‐high [PM 10 : OR = 1.10, 95% CI 1.04–1.16; WQS: OR = 1.41, 95% CI 1.09–1.82] and increasing [PM 1.0 : OR = 1.44, 95% CI 1.06–1.98; PM 2.5 : OR = 1.10, 95% CI 1.02–1.19; PM 10 : OR = 1.10, 95% CI 1.06–1.13; WQS: OR = 1.21, 95% CI 1.01–1.45]) compared to the stable‐low symptoms trajectory. Loneliness contributed to 26.73%–29.73% of the associations between PM exposure and depressive symptom trajectories. Conclusion Exposures to individual and mixed PM pollutants increase the risk of severe depressive symptom trajectory groups, and reducing loneliness alleviates these effects. The findings underscore the need for further coordinated control of PM pollutants and alleviating loneliness to prevent depressive symptoms.