Gender Differences in the Protective Effects of Social Participation on Depressive Symptom Trajectories Among Middle-Aged and Older Adults in China: A Nationwide Longitudinal Study

Background/Objectives: Against the background of the rapid aging of the population, the symptoms of depression are a major health problem for middle-aged and older adults. This study analyzes the relationship between social participation and the trajectory of depressive symptoms and whether this association varies by gender. Methods: The data comes from five rounds of surveys conducted by the China Health and Retirement Longitudinal Study (CHARLS) from 2011 to 2020, including a total of 5796 participants aged 45 or above. The depressive symptoms of each wave are measured using the 10-item Center for Epidemiologic Studies Depression Scale (CESD-10). Social participation was defined as the number of reported activities (0, 1, or ≥2). The development trajectory of depressive symptoms was analyzed through Group-Based Trajectory Modeling (GBTM), and their links with social participation level were subsequently quantified using multinomial logistic regression. Gender differences were assessed via interaction tests and stratified models. Results: GBTM identified four distinct depressive symptom trajectories: low (29.71%), moderate (42.72%), increasing (22.07%), and high (5.50%). Compared with no participation, engaging in one activity was linked to lower odds of falling into the moderate, increasing, and high trajectories; the association was stronger for ≥2 activities. Gender-stratified analyses revealed substantial heterogeneity (all interaction p < 0.01). Among women, single-activity participation was associated with lower odds across all three adverse trajectories. Among men, similar associations required ≥2 activities, with single-activity participation linked only to lower odds of the high trajectory. Conclusions: Higher levels of social participation have significantly reduced the depressive symptoms of middle-aged and older adults, and the gender differences are pronounced. Interventions should improve access to social participation for older women and promote activity diversity for older men.