Objective: To assess the effect of socioeconomic status (SES) on outcomes in patients with early inflammatory arthritis, using data from the Canadian Early Arthritis Cohort (CATCH) study.
Methods: In an incident cohort, 2023 patients were recruited, and allocated to low SES or high SES groups based on education and income. Outcomes at baseline and 12 months were analyzed in relation to SES including the 28-joint Disease Activity Score (DAS28), Simplified Disease Activity Index (SDAI), pain, patient's global assessment scale (PtGA), the Health Assessment Questionnaire-Disability Index (HAQ-DI), and the SF12-v2 Health Survey, using the ANOVA, chi-squared test, and regression analyses.
Results: The CATCH population had 43% with high school education or less and 37% in the low-income group (< 50,000 Can$ per annum household income). The low-education group had higher DAS28 at baseline (p = 0.045), becoming nonsignificant at 12 months and lower physical component score on SF12-v2 at baseline (p = 0.022). Patients in the low-income group presented with higher HAQ-DI (p = 0.017), pain (p = 0.035), PtGA (p = 0.004), and SDAI (p = 0.022). Low-income versus high-income groups were associated with an OR above the median for HAQ-DI (1.20; 95% CI 1.00-1.45), PtGA (1.27; 95% CI 1.06-1.53), and SDAI (1.25; 95% CI 1.02-1.52) at baseline. The association with low income persisted at 12 months for HAQ-DI (OR 1.30; 95% CI 1.02-1.67), but not for other variables.
Conclusion: Low SES was initially associated with higher disease activity, pain, and PtGA, and poorer function. At 1 year, outcomes were similar to those with high SES, with the exception of HAQ-DI.
Keywords: EARLY RHEUMATOID ARTHRITIS; EDUCATION; INCIDENT COHORT; INCOME; REMISSION; SOCIOECONOMIC STATUS.