Background/Purpose: Rheumatoid Arthritis (RA) is associated with a high prevalence of comorbidities, negatively affecting outcomes like disease activity and physical function. However, not all comorbid conditions have the same impact on the outcomes of interest. The Rheumatic Diseases Comorbidity Index (RDCI) was validated to measure more accurately the burden and prognostic impact of overall comorbidity, based on a weighted preselection of comorbid conditions. We aimed to quantify the total burden of comorbidities, its association with disease outcomes, demographics and Serious Adverse Events (SAE) in early RA.

Methods: The presence of comorbidities was recorded on screening, before treatment initiation in 379 patients with recently diagnosed RA (<1 year) participating in the Care in early RA (CareRA) trial. The RDCI (0-9) was calculated by scoring 11 weighted comorbid conditions. Demographics including gender, age, smoking status, alcohol use and BMI were registered on screening. Disease activity (DAS28-ESR/CRP) was measured at baseline and after 1 year treatment using a treat-to-target approach. All SAE were registered during a 2-year follow-up. The association of RDCI with disease activity, functional disability (HAQ-DI), demographics and SAE was explored by assessing Spearman correlations. Correlations ≤0.29 were considered small, 0.30-0.49 moderate and ≥0.50 strong. Additionally, a multivariate linear regression analysis was performed to control for confounders.

Results: Out of 379 patients, slightly more than half (55.9%) had a RDCI equal to zero. The mean score was 0.8 and the maximum 6. RDCI scores of 1, 2 or ≥3 were obtained in 65 (17.2%), 70 (18.5%) and 32 (8.4%) participants respectively. The most frequent comorbidities were hypertension (22.4%), cardiovascular events (myocardial infarction/stroke or other) (16.6%) and lung diseases (8.4%). A moderately positive correlation was found between RDCI and age (r = 0.39, p<0.001). RDCI also correlated with disease activity (DAS28-CRP and DAS28-ESR) (r = 0.19-0.21, p<0.001) and with physical functioning (HAQ-DI) (r = 0.13, p=0.009) at baseline. After 1 year no more statistically significant correlation was found between the RDCI and DAS28-CRP, DAS28-ESR or HAQ-DI scores. In addition, RDCI correlated positively with the amount of SAE per patient, occurring during this 2-year study (r = 0.24, p<0.001). Multivariate linear regression confirmed these findings. RDCI was significantly associated with DAS28-CRP at baseline (β=0.127, p=0.034), and amount of SAE per patient (β=0.109, p=0.001) when controlled for gender, age, smoking status, alcohol use, BMI and treatment strategy.

Conclusion: At disease onset, almost half of RA patients in our study population had at least one clinically important comorbidity, as assessed by the RDCI. Scores of this co-morbidity index were positively correlated with age, disease activity and functional ability at baseline, but this correlation disappeared after one year treatment with intensive remission induction strategies. The incidence of SAE was associated with RDCI, reflecting an important impact of comorbidities on patients’ overall health evolution.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/assessment-of-the-burden-of-comorbidities-by-the-rheumatic-disease-comorbidity-index-in-early-rheumatoid-arthritis-patients-at-disease-onset/