Autoimmune smoke and fire--coexisting rheumatoid arthritis and chronic obstructive pulmonary disease: a cross-sectional analysis.

To assess the association between RA and chronic obstructive pulmonary disease (COPD) in a population-based case-control study. A cross-sectional analysis performed utilizing the database of Clalit Health Services, the largest healthcare provider organization in Israel. Patients over the age of 20 years who were diagnosed with RA ('cases') and who were treated with any anti-rheumatic drug were compared with a sample of age- and gender-matched enrollees ('controls') without regard for the prevalence of COPD. Data on health-related lifestyles and other comorbidities were collected. χ(2), t tests, and logistic regression models were used to compare the study groups. The study included 9,039 RA cases and 15,070 controls. The proportion of COPD was significantly higher in patients with RA as compared to the control group (8.6 vs. 4.4%, p < 0.0001, odds ratio (OR) 2.06, 95% confidence interval (CI) 1.85-2.29). A multivariate logistic regression model demonstrated that RA was significantly associated with COPD, after controlling for confounders, including age, sex, socioeconomic status, smoking, and obesity (adjusted OR 1.98, 95% CI 1.77-2.21, p < 0.0001). In this large data-based study, RA was found to be associated with COPD.