Prognostic value of comorbidity indices and lung diseases in early rheumatoid arthritis: a UK population-based study

Objectives: We assessed comorbidity burden in people with rheumatoid arthritis (RA) at diagnosis and early disease (three years) and its association with early mortality and joint destruction. The association between lung disease and mortality in RA in not well studied; we also explored this relationship.

Methods: From a contemporary UK based population (n=1,475,762) we identified a cohort with incident RA (n=6,591). The prevalence of comorbidities at diagnosis of RA and at three years compared with an age and gender matched controls (n=6,591). In individuals with RA we assessed the prognostic value of the Charlson Comorbidity Index (CCI) and Rheumatic Disease Comorbidity Index (RDCI) calculated at diagnosis for all-cause mortality and joint destruction (with joint surgery as a surrogate marker). We separately evaluated the association between individual lung diseases (chronic obstructive pulmonary disease [COPD], asthma, and interstitial lung disease) and mortality.

Results: Respiratory disease, cardiovascular disease, stroke, diabetes, previous fracture, and depression were more common (p<0.05) in patients with RA at diagnosis than controls. Comorbidity (assessed using RDCI) was associated with all-cause mortality in RA (adjusted hazard ratio [HR] 1.26, 95% confidence interval [CI] 1.00-1.60). There was no association with joint destruction. COPD, but not asthma, was associated with mortality (COPD HR 2.84, 95% CI 1.13-7.12).

Conclusion: There is an excess burden of comorbidity at diagnosis of RA including COPD, asthma and ILD. COPD is a major predictor of early mortality in early RA. Early assessment of comorbidity including lung disease should form part of the routine management of RA patients.