Decline in Incidence of Extra‐Articular Manifestations of Rheumatoid Arthritis: A Population‐Based Cohort Study

OBJECTIVE: The focus of this study was to assess changes in the cumulative incidence of extra-articular manifestations of rheumatoid arthritis (ExRAs) and associated mortality risk. METHODS: This study evaluated trends in occurrence of ExRAs using a population-based inception cohort that included all adult patients with incident rheumatoid arthritis (RA) from 1985 through 2014 meeting the 1987 American College of Rheumatology criteria. Patients were divided into two cohorts based on the incidence date of RA, 1985 to 1999 and 2000 to 2014. The occurrence of ExRAs was determined by manual chart review, and the 10-year cumulative incidence was estimated for each ExRA in both cohorts. Cox proportional hazard models were used to determine associations between specific demographic and RA disease characteristics and ExRAs and between ExRAs and mortality. RESULTS: There were 907 patients included, 296 in the 1985 to 1999 cohort and 611 in the 2000 to 2014 cohort. The 10-year cumulative incidence of any ExRA decreased significantly between the earlier and later cohorts (45.1% vs 31.6%, P < 0.001). This was largely driven by significant declines in subcutaneous rheumatoid nodules (30.9% vs 15.8%, P < 0.001) and nonsevere ExRAs (41.4% vs 28.8%, P = 0.001). Identified risk factors for the development of any ExRAs include rheumatoid factor positivity (hazard ratio HR 2.02, 95% confidence interval CI 1.43-2.86) and current smoking (HR 1.61, 95% CI 1.10-2.34). Mortality was increased in patients with either nonsevere (HR 1.83, 95% CI 1.18-2.85) or severe ExRAs (HR 3.05, 95% CI 1.44-6.49). CONCLUSIONS: The incidence of ExRAs has decreased over time. Mortality remains increased in patients with ExRAs.