Higher comorbidities associated with less improvement in disease activity in early RA: results from CATCH cohort

OBJECTIVES: Comorbidities negatively influence remission rates in RA. This study estimated the effects of comorbidities on components of disease activity in early RA (ERA). METHODS: Using the Rheumatic Disease Comorbidity Index (RDCI), the influence of comorbidities on trajectories of components of the SDAI (Simple Disease Activity Index) was assessed in participants with ERA enrolled in Canadian Early Arthritis Cohort (CATCH) over the first year of treatment. Adjusted effects of RDCI scores categorized 0, 1, 2 and ≥3 on SDAI trajectories over time were analysed using multivariable generalized estimating equations (GEEs) models adjusted for multiple confounders. RESULTS: ERA participants (N = 2248) had a mean (S.D.) symptom duration of 5.7 (3) months; mean age 55 (15) years and 72% were female. Baseline SDAI was 29 (15), with 90% having moderate-high SDAI. Baseline RDCI scores were 0 in 888 (40%), 1 in 547 (24%), 2 in 451 (20%) and ≥3 in 362 (16%). While baseline disease activity was similar across comorbidity groups, patients with higher RDCI scores showed worse SDAI trajectories over the first year of RA treatment. Higher RDCI scores were independently associated with pain, patient and physician global assessments over time. CONCLUSION: This large real-world analysis of ERA patients seen in routine rheumatology practice across Canada showed that while RA disease activity across comorbidity groups at diagnosis was similar, higher comorbidity was associated with slower improvement in RA disease activity over the first year of treatment, likely driven by independent associations with patient and physician global assessments and pain.