Chronic obstructive pulmonary disease and rheumatoid arthritis: severe exacerbations, pneumonia, and death in a population-based cohort

Objective: Respiratory disease contributes to the excess mortality seen in rheumatoid arthritis (RA), and chronic obstructive pulmonary disease (COPD) is frequently encountered. The aim of this study was to investigate the risk of severe acute exacerbation, pneumonia, and death among patients with RA and COPD compared with patients with COPD alone. Method: The study population was patients with hospital-based, outpatient follow-up for COPD identified from the Danish COPD registry. Diagnoses of RA, information about hospitalizations for acute exacerbations of COPD (AECOPD), pneumonia, and vital status were obtained from National Health Registries. Follow-up was 12 months after first outpatient contact for COPD. Hospitalizations for AECOPD and pneumonia, and risk of death in COPD with or without RA, were compared using Cox proportional hazards regression analysis. Covariates were balanced using inverse probability of treatment (IPT) weighting. Results: The study included 58 655 patients with hospital-based follow-up for COPD, 2033 (3.5%) of whom had RA. More than 25% of the cohort experienced hospitalization with AECOPD and/or pneumonia in the first year after first outpatient COPD hospital contact. IPT-weighted unadjusted Cox regression analysis showed similar risk of hospitalization with AECOPD among patients with RA and COPD [hazard ratio (HR) 1.004, 95% confidence interval (CI) 0.89–1.13] and death (HR 1.13, 95% CI 0.98–1.30), but increased risk of hospitalization for pneumonia (HR 1.26, 95% CI 1.11–1.42). Conclusion: The increased risk of pneumonia associated with RA may be attributed to immunosuppression. The findings should lead to increased focus on optimizing COPD therapies and preventive measures.