Longitudinal association between social economic status and new-onset arthritis among middle-aged and elderly adults: evidence from the CHARLS cohort

Arthritis represents a major global health burden, with social economic status (SES) emerging as a critical determinant. However, longitudinal evidence from Asian populations remains limited. This prospective cohort study used China Health and Retirement Longitudinal Study (CHARLS) data, including 4,469 arthritis-free participants aged ≥ 45 years from baseline (2011) through 2018. SES was assessed using composite scores combining education and household wealth, categorized into four groups. New-onset arthritis was determined by self-reported physician diagnosis. Covariates included demographics, lifestyle factors, anthropometrics, and comorbidities. Multivariable logistic and Cox regression models estimated odds ratios (ORs) and hazard ratios (HRs) with 95% confidence intervals (CIs). Kaplan-Meier analysis estimated cumulative incidence with log-rank tests. Subgroup analyses examined effect modification by gender and age. During 7-year follow-up, 1,324 participants (29.6%) developed arthritis. In fully adjusted models, compared with low SES, upper-middle SES demonstrated reduced risk in both logistic (OR = 0.67, 95% CI: 0.55–0.82, P < 0.001) and Cox regression (HR = 0.71, 95% CI: 0.60–0.84, P < 0.001). High SES showed greater protection (OR = 0.41, 95% CI: 0.14-1.00; HR = 0.44, 95% CI: 0.18–1.08). Kaplan-Meier analysis showed cumulative incidence decreased across SES groups: 34.5% (low), 31.1% (low-middle), 23.5% (upper-middle), and 14.3% (high SES; log-rank P < 0.0001). Effects remained consistent across gender and age subgroups. Higher SES was independently associated with reduced arthritis risk among Chinese middle-aged and elderly adults, demonstrating a clear dose-response relationship. These findings support targeted prevention strategies for socioeconomically disadvantaged populations.