This paper […] is an important wake-up call: the environment is likely an essential contributor to pain and inflammation in the patients for whom we care
Josef Smolen
Previous epidemiological studies have shown an association between air pollution and an increased risk of developing RA. A team of investigators in South Korea has conducted research to evaluate the effects of air pollution on disease activity and flare occurrence in patients with established RA and explore its underlying mechanisms.
In an accompanying editorial Jeffrey A. Sparks, MD, MMSc, Division of Rheumatology, Inflammation, and Immunity, Mass General Brigham / Brigham and Women’s Hospital, and Harvard Medical School, comments, “This is one of the largest studies to use robust methods to link air pollutants with RA disease activity. Considering rising levels of air pollutants, these results have significant clinical, biologic, and public health implications. They also further reinforce that inhalants may have broad implications for risk and progression of RA and perhaps other autoimmune diseases. From a clinical perspective, this may offer avenues to lower the risk of RA flares by avoiding air with poor quality and provide some potential explanation for otherwise idiosyncratic RA flares.”
This prospective cohort study tracked 1,070 RA patients across 12,583 real-world outpatient visits over four years (2021–2024) at a major South Korean medical center. Air pollution exposure was estimated using monthly concentrations of six major air pollutants (sulfur dioxide, SO2; nitrogen dioxide, NO2; ozone, O3; carbon monoxide, CO; paritculate matter with a diameter of 10 µm, PM10; and paritculate matter with a diameter of 2.5 µm,PM2.5), which were matched with disease activity and flare outcomes longitudinally recorded at each outpatient visit.
The statistical analysis was adjusted for demographic characteristics, serologic status (the presence of specific antibodies typical for RA in the blood), medication use, socioeconomic factors, and meteorological variables. For sensitivity analysis to better control for time-invariant confounding and avoid potential reverse causation inherent in the monthly analysis, a case-crossover design using daily air pollutant concentrations preceding each visit was applied, using conditional logistic regression to assess changes within the same patient.
“Our study found that higher PM2.5 concentration was associated with increased disease activity and flare risk, notably prolonged exposure to elevated PM2.5 over more than two weeks,” explains lead investigator Eun Bong Lee, MD, PhD, Division of Rheumatology, Department of Internal Medicine, Seoul National University College of Medicine, and Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Republic of Korea.
