Adolescent sports participation and social-class health inequalities: evidence from CHNS

Purpose: Health inequalities rooted in social stratification remain a persistent structural public-health challenge. While physical activity is recognized as a health-enhancing behavior, limited longitudinal evidence exists on how its effects vary across social classes. This study examines the life-course interactions among social class, physical-activity participation, and aging, and evaluates whether youth physical activity mitigates class-based health disparities. Methods: Data were drawn from five waves (1997, 2000, 2004, 2006, and 2015) of the China Health and Nutrition Survey (CHNS), comprising 39,672 individuals and 180,696 person-year observations. Growth-curve models were used to estimate trajectories of self-rated health and assess the interactive effects of social class, physical activity, and age, controlling for demographic characteristics. Results: Health inequalities exhibited structural rigidity: health gradients between social strata widened from 1997 to 2015, and early-life disparities persisted throughout aging, forming "parallel trajectories." Physical activity effects differed significantly by class. Lower-stratum individuals benefited little due to structural constraints; middle-stratum participants showed a "health-behavior paradox," where participation correlated with steeper health decline; upper-stratum groups demonstrated negligible marginal gains due to resource saturation. Conclusion: Universal sports-promotion strategies are insufficient to reduce entrenched health inequalities. Structural reforms addressing socioeconomic constraints, combined with class-sensitive behavioral interventions, are essential to disrupt the reproduction of health disparities and promote equitable healthy aging across the life course.