How Do Comorbidities Impact Disease Activity in the First Year of RA Treatment?

In a study, researcher aimed to identify the relationship between comorbidities and Simple Disease Activity Index (SDAI) scores among patients with early rheumatoid arthritis (ERA). These findings were presented at the American College of Rheumatology (ACR) Convergence 2021.

The researchers investigated comorbidity burden over the first year of conventional synthetic disease-modifying anti-rheumatic drug (DMARD) use among patients in the Canadian Early Arthritis Cohort. Comorbidity was defined via the Rheumatic Disease Comorbidity Index (RDCI).

The total cohort comprised 2,248 patients with a mean symptom duration of 5.71 months. The average age was 55 years and 72% of the cohort were female. Nearly three-quarters of patients were treated with methotrexate, and 60% also received other conventional DMARDs. At baseline, the mean SDAI score was 29, with 90% of patients classified as having moderate-high SDAI. Additionally, baseline RDCI scores of zero, one, two, or three were reported in 40%, 24%, 20%, and 16% of participants, respectively.

Disease activity was not found to differ according to comorbidity status. However, an RDCI of zero was associated with a greater rate of change in SDAI scores, patient global assessment (PtGA) scores, physician global assessment (MDGA) scores, and pain levels over time compared with patients who had multiple RDCI conditions (P<0.05). For patients with an RDCI of one and two, the researchers observed a significantly greater rate of change in swollen joint count compared with patients with higher RDCI scores (P=0.01). RDCI was not significantly associated with change in tender joint count and C-reactive protein over the follow-up period.

“In this ERA cohort, having multiple comorbidities was associated with worse improvement and disease activity assessed by SDAI over the first year of treatment,” wrote the authors in their conclusion. “Swollen joint count, PtGA, and MDGA were the components of SDAI that were most influenced by the presence of comorbidities. The results demonstrate a negative effect of having comorbidities at disease onset of RA on the evolution of both patients and physicians reported outcomes.”

Source: Chen L, et al. The Impact of Comorbidities on the Simple Disease Activity Index (SDAI) and Its Components over the First Year of Follow-up – an Analysis from the Canadian Early Arthritis Cohort (CATCH). Arthritis Rheumatol. 2021;73(suppl 10). Presented at ACR Convergence 2021 (Virtual), Nov. 5-9, 2021.