PM<sub>10</sub> increases mortality risk in rheumatoid arthritis-associated interstitial lung disease
Soo Han Kim, Sun‐Young Kim, Hee‐Young Yoon, Jin Woo Song
Abstract
Objectives The effect of air pollution on the prognosis of rheumatoid arthritis-associated interstitial lung disease (RA-ILD) remains poorly understood. We aimed to evaluate the effect of long-term exposure to particulate matter with an aerodynamic diameter of ≤10 µm (PM 10 ) and nitrogen dioxide (NO 2 ) on mortality in patients with RA-ILD. Methods We included 309 patients (mean age, 61.7 years; male, 44.3%) with RA-ILD. Individual-level long-term exposures to PM 10 and NO 2 at their residential addresses were estimated using a national-scale exposure prediction model. The effect of the two air pollutants on mortality was estimated using a Cox-proportional hazards model adjusted for individual-level and area-level characteristics. Results The median follow-up period was 4.8 years, and 40.8% of patients died or underwent lung transplantation. The annual average concentrations of PM 10 and NO 2 were 56.3 μg/m 3 and 22.4 ppb, respectively. When air pollutant levels were stratified by quartiles, no association was observed between air pollutant concentration and mortality in patients with RA-ILD. However, when stratified by two groups (high exposure (top 25th percentile) vs low exposure (bottom 75th percentile)), we observed a significant association between high PM 10 exposure and mortality (HR 1.68; 95% CI 1.11 to 2.52; p=0.013) but no association between NO 2 exposure and mortality. In the subgroup analyses, the effect of high PM 10 exposure on mortality was significant in patients aged <65 years (HR 1.98; 95% CI 1.02 to 3.85; p=0.045). Conclusions Our results indicated that high PM 10 exposure may be associated with mortality in patients with RA-ILD.