Comorbidities and treatment patterns in early rheumatoid arthritis: a nationwide Swedish study

OBJECTIVE: To examine how comorbidities in patients with early rheumatoid arthritis (RA) associate with use of different disease-modifying antirheumatic drugs (DMARDs). METHODS: We used Swedish nationwide clinical and quality registers to collect comorbidity data for patients diagnosed with RA during 2006–2019 (n=13 505). We compared the use of DMARDs at diagnosis and after 1 year, in relation to comorbidity categories 5 years prior to RA diagnosis and overall comorbidity burden. For each comorbidity category, we also calculated adjusted ORs of being on treatment with other (or no) DMARDs compared with methotrexate (MTX) monotherapy 1 year after RA diagnosis. RESULTS: At RA diagnosis, 68% (n=9178) of all patients were treated with MTX monotherapy, with the lowest proportion in patients with chronic kidney (CKD, 48%, n=50) and respiratory diseases (57%, n=413). At 1 year, most patients still received MTX monotherapy (<11% decrease, across all comorbidity categories). At 1 year, 13% received biological/targeted synthetic DMARDs, with the lowest proportion among patients with malignant diseases (OR=0.69, 95% CI=0.51 to 0.95). Being without DMARD at 1 year was more common among patients with CKD (OR=3.25, 95% CI=2.20 to 4.81), respiratory diseases (OR=1.83, 95% CI=1.32 to 2.53) or a history of hospitalisation due to infection (OR=1.47, 95% CI=1.23 to 1.75), and among patients with higher comorbidity burden and older age. CONCLUSION: In a nationwide setting with universal healthcare, most comorbid conditions do not limit the initiation or continuation of MTX or other DMARDs in early RA, although patients with certain comorbid conditions, higher comorbidity burden and higher age were somewhat less intensively treated.