Inflamed airways are hypothesized to contribute to rheumatoid arthritis (RA) pathogenesis due to RA-related autoantibody production, and smoking is the strongest environmental RA risk factor. However, the role of chronic airway diseases in RA development is unclear. We investigated whether asthma or COPD were associated with RA.
We performed a prospective cohort study of 205,153 women in the Nurses’ Health Study (NHS, 1988-2014) and NHSII (1991-2015). Exposures were self-reported physician-diagnosed asthma or COPD confirmed by validated supplemental questionnaires. Outcomes were incident RA confirmed by medical record review by 2 rheumatologists. Covariates (including smoking pack-years/status) were assessed via biennial questionnaires. Multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) for RA were estimated using Cox regression.
We identified 15,148 women with confirmed asthma, 3,573 with confirmed COPD, and 1,060 incident RA cases during 4,384,471 person-years of follow-up in NHS and NHSII. Asthma was associated with increased RA risk (HR 1.53, 95%CI 1.24,1.88) compared to no asthma/COPD after adjusting for covariates including smoking pack-years/status. Asthma remained associated with increased RA risk among never-smokers only (HR 1.53, 95%CI 1.14,2.05). COPD was also associated with increased RA risk (HR 1.89, 95%CI 1.31,2.75). The association of COPD with RA was most pronounced in the subgroup of ever-smokers aged >55 years (HR 2.20, 95%CI 1.38,3.51).
Asthma and COPD were each associated with increased risk for incident RA, independent of smoking status/intensity and other potential confounders. These results provide support for the hypothesis that chronic airway inflammation may be crucial in RA pathogenesis.