Increased risk of chronic obstructive pulmonary disease in patients with rheumatoid arthritis: a population-based cohort study

Background: The role of autoimmune pathology in development and progression of chronic obstructive pulmonary disease (COPD) is becoming increasingly popular. Our aim was to assess the association between patients with rheumatoid arthritis (RA) and subsequent COPD risk in a nationwide population. Method: We conducted a retrospective cohort study using data from the National Health Insurance system of Taiwan. The RA cohort included patients who were newly diagnosed and recruited between 1998 and 2008. Each patient was randomly frequency-matched for age, sex and the year of index date with people without RA from the general population. The newly diagnosed COPD was followed up until the end of 2010. The relative risks of COPD were estimated using Cox proportional hazard models after adjusting for age, sex, index year and comorbidities. Result: The overall incidence rate of COPD was 1.74-fold higher in the RA cohort than in the non-RA cohort (5.25 vs. 3.01 per 1000 person-years, 95% confidence interval (CI) = 1.68–1.81). Age-related risk analysis showed an increased incidence of COPD with age in both RA and non-RA cohorts. However, adjusted hazard ratio (HR) maximum was witnessed in the age range of 20–34 years (adjusted HR: 7.67, 95% CI=1.94–30.3), whereas adjusted HR minimum was observed in the oldest age group (>65 years). Conclusion: Patients with RA have a significantly higher risk of developing COPD than that of the control population. Further, age-related risk analysis indicated much higher adjusted HR in younger patients although COPD incidence increased with age. It can be hypothesized that in addition to cigarette smoke, RA may be a determining factor for COPD incidence and/or facilitates shortening of the time course for developing COPD. However, further investigation is needed to corroborate this hypothesis.