RESEARCHERS have found that higher exposure to fine particulate air pollution is linked to increased disease activity and a greater risk of flares in people with rheumatoid arthritis, based on four years of cohort follow-up.
Researchers conducted a prospective cohort study of patients with rheumatoid arthritis treated at a tertiary medical centre in South Korea between January 2021 and December 2024. Air pollution exposure was estimated using monthly mean concentrations of six pollutants: sulfur dioxide, nitrogen dioxide, ozone, carbon monoxide, and particulate matter of two size fractions, PM10 and PM2.5.
Disease activity and flares were recorded longitudinally at each outpatient visit, and associations with air pollution were analysed using linear and logistic generalised estimating equations, adjusted for demographic, serologic, medication, socioeconomic, and meteorological factors. A case-crossover sensitivity analysis using daily pollutant concentrations preceding each visit was also conducted.
A total of 12,583 outpatient visits from 1,070 patients were analysed. Among the six pollutants assessed, PM2.5 was significantly associated with an increased risk of flare (adjusted odds ratio 1.113, 95% CI 1.017 to 1.218) and with higher scores on several disease activity measures, including the Disease Activity Score based on 28 joints with C-reactive protein, the Clinical Disease Activity Index, and tender and swollen joint counts. The association between PM2.5 and disease activity was more pronounced among women and nonsmokers. In the case-crossover analysis, prolonged cumulative exposure to PM2.5 over more than two weeks was associated with an increased risk of flare.
These findings have provided real-world evidence that air pollution, particularly PM2.5, may be associated with worsening rheumatoid arthritis disease activity. As this was an observational cohort study, causality cannot be established, and further external validation has been called for.
The authors have suggested that physicians should encourage patients with rheumatoid arthritis to minimise exposure to poor air quality, and that policymakers should prioritise air quality improvement to help reduce the burden of chronic illnesses, including rheumatoid arthritis flares.
Reference
Jung SC et al. Effects of air pollution on disease activity in patients with rheumatoid arthritis. Annals of the Rheumatic Diseases. 2026; DOI:10.1016/j.ard.2026.06.018.
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