Long-term exposure to traffic-related air pollution and systemic lupus erythematosus in Taiwan: A cohort study.

Systemic lupus erythematosus (SLE) is a multi-systemic chronic autoimmune disease, the etiology of SLE is still unclear. Only a few studies evaluated the associations between air pollution and SLE. We conducted a population-based cohort study in Taiwan to examine the associations of air pollution with SLE. A total of 682,208 individuals aged 18-70 years were retrieved from National Health Insurance Research Database. We applied 1-km resolution land use regression and satellite-based models to estimate air pollutant concentrations during 2001-2010. The mixed effect Cox models with time-dependent variables were performed to estimate the associations between air pollution and SLE, as hazard ratios (HRs) with 95% confidence interval (CI). We identified 1292 newly diagnosed SLE patients with average age of 43.26 ± 13.64 years, most of them were female. There were positive associations of SLE with exposure to a 9.76 ppb increase in nitrogen dioxide (NO2), a 0.20 ppm increase in carbon monoxide (CO), and a 10.2 μg/m3 increase in fine particles (PM2.5) (HR = 1.21, 95% CI: 1.08-1.36, HR = 1.44, 95% CI: 1.31-1.59, and HR = 1.12, 95% CI: 1.02-1.23, respectively). Additionally, we observed negative associations with ozone (O3) and sulfur dioxide (SO2). According to the exposure-response relationships, exposure to NO2 between 28 and 38 ppb, exposure to CO above 0.6 ppm, and exposure to PM2.5 between 18 and 46 μg/m3 were positively associated with SLE. The results suggested that long-term exposure to traffic-related gaseous air pollutants (NO2 and CO) less than current National Ambient Air Quality Standards and PM2.5 are significantly associated with the risk of SLE.