Ambient air pollution exposures and risk of rheumatoid arthritis: results from the Swedish EIRA case–control study. Issue 6 (24th July 2012) - Hart, Jaime E
Abstract : Objective: Environmental factors may play a role in the development of rheumatoid arthritis (RA). We examined whether long-term exposures to air pollution were associated with the risk of RA in the Swedish Epidemiological Investigation of Rheumatoid Arthritis Study. Methods: We studied 1497 incident RA cases and 2536 controls. Local levels of particulate matter (PM10 ) and gaseous pollutants (sulphur dioxide (SO2 ) and nitrogen dioxide (NO2 )) from traffic and home heating were predicted for all residential addresses. We examined the association of an IQR increase (2 µg/m 3 for PM10, 8 µg/m 3 for SO2 and 9 µg/m 3 for NO2 ) in each pollutant at different time points before symptom onset and average exposure with the risk of all RA and the risk of the rheumatoid factor and anti-citrullinated protein antibody (ACPA) RA phenotypes. Results: There was no evidence of an increased risk of RA with PM10 . Total RA risks were modestly elevated for the gaseous pollutants, but were not statistically significant after adjustment for smoking and education (OR 1.18, 95% CI 0.97 to 1.43 and OR 1.09, 95% CI 0.99 to 1.19 for SO2 and NO2 in the 10th year before onset). Stronger elevated risks were observed for individuals with less than a university education and with the ACPA-negative RA phenotype. Conclusions: No consistent overall associations between air pollution in the Stockholm area and the risk of RA were observed. However, there was a suggestion of increased risks of RA incidence with increases in NO2 from local traffic and SO2 from home heating sources with stronger associations for the ACPA-negative phenotype.