Association of socioeconomic status with treatment delays, disease activity, joint damage, and disability in rheumatoid arthritis

Objective To examine the association of socioeconomic status (SES) and delays in disease-modifying antirheumatic drug (DMARD) treatment with clinical measures in rheumatoid arthritis (RA) patients. Methods RA patients were recruited from rheumatology practices. We assessed SES based on education, occupation, and income, and divided patients into tertiles. The time from RA symptom onset to DMARD initiation (DMARD lag) was determined by self-report of the 2 dates, and distance to the rheumatologist (Distance) was obtained from Google Maps. We examined disease activity, determined by the Disease Activity Score in 28 joints using the erythrocyte sedimentation rate (DAS28-ESR); joint damage, determined from hand radiographs by Sharp scores; and physical disability, determined by the modified Health Assessment Questionnaire (M-HAQ). We used linear regression models to examine the relationship between clinical measures and SES, Distance, and DMARD lag. Results We recruited 1,209 RA patients, 1,159 of whom had received DMARD treatment. Mean-±-SD DMARD lag was 6.9-±-9.0 years. On average, patients with lower SES waited 8.5-±-10.2 years after onset of RA symptoms to begin DMARD treatment, compared to those in the middle and upper SES tertiles who waited 6.1-±-7.9 years (P-=-0.002) and 6.1-±-8.6 years (P-=-0.009), respectively. Each year of delayed treatment was associated with a DAS28-ESR increase of 0.02 (P-≤-0.001), a Sharp score increase of 1.33 (P-≤-0.001), and an M-HAQ score increase of 0.01 (P-≤-0.001). Conclusion Low SES was associated with delay in DMARD initiation, and both were independently associated with worse clinical measures in RA. Strategies to reduce treatment delay in low-SES RA patients are needed.