Background Exposure to air pollutants is associated with an increased risk of pulmonary and cardiovascular disease and death. Because few studies have investigated the effects of air pollution on systemic lupus erythematosus (SLE), we investigated the association between exposure to air pollutants, including particulate matter (PM), and disease activity over 1 year in a prospective, longitudinal cohort of Korean patients with SLE.

Methods The study enrolled 386 patients from three metropolitan regions in Korea. The daily average PM10, PM2.5, NO2, CO, SO2, and O3 concentrations were measured using portable air quality monitors and data from the National Ambient Air Monitoring System. Disease activity was evaluated using the SLE Disease Activity Index 2000 (SLEDAI-2K) and Physician Global Assessment (PGA), every 3 months for 1 year. Lupus flares, a damage index, and 36-Item Short Form Health Survey (SF-36) scores were also assessed. A generalized estimating equation was used to evaluate the impact of air pollutants on clinical outcomes, including disease activity.

Results Changes in PM10 and PM2.5 were significantly associated with changes in SLEDAI-2K scores of > 8 over 1 year in SLE patients (β = 0.097, 95% confidence interval [CI]: 0.048–0.146, p < 0.001; β = 0.100, 95% CI: 0.054–0.146, p < 0.001, respectively). Changes in PM10 and PM2.5 were also significantly associated with the development of lupus flares (β = 1.603, 95% CI: 1.067–2.408, p = 0.023; β = 1.777, 95% CI: 1.048–3.011, p = 0.033, respectively). However, there were no significant associations between the changes in NO2, CO, SO2, and O3 and lupus activity.

Conclusions In this study, PM10 and PM2.5 exposure increased disease activity and the risk of lupus flares in SLE patients living in metropolitan regions.