Background/Purpose: While air pollution has been implicated in the pathogenesis of rheumatoid arthritis (RA), its association with RA disease activity remains insufficiently investigated (1, 2). We aimed to evaluate the effect of air pollution on disease activity and flare occurrence in patients with RA.

Methods: This prospective study included patients with RA who visited a tertiary medical center in South Korea between January 2021 and October 2024, with at least 6 months of follow-up. Air pollution levels were assessed using monthly mean concentrations of six air pollutants (SO2, NO2, O3, CO, PM10, and PM2.5) obtained from the Korean National Institute of Environmental. RA disease activity was evaluated using the tender joint count, swollen joint count based on 28 joints (TJC28, SJC28), clinical disease activity Index (CDAI), and disease activity score based on 28 joints (DAS28). Flare events were defined based increases in DAS28 scores. Associations between air pollution and RA disease activity or flare occurrence were analyzed using linear and logistic generalized estimating equations (GEE), accounting for repeated measures within the study population and adjusting for prespecified covariates including age, sex, smoking status, serologic status, dose of concomitant glucocorticoids, type of disease-modifying anti-rheumatic drugs (DMARDs), and climate variables (temperature and humidity).

Results: A total of 1,056 RA patients were included, with a mean (SD) age of 61.2 (12.7) years, and 907 (85.9%) were female. Patients contributed data for a median (IQR) of 11.0 (8.0, 13.0) visits. There were 1,724 flare events during the observation period, with an incidence rate of 56.3 per 100 person-years (95% CI: 53.7 to 59.1). Air pollution concentrations were high in winter and spring and low in summer (Figure 1). Increases in PM10, and PM2.5 levels were associated with flare occurrence (Table 1). Among individual pollutants, O3 was associated with SJC28 and CDAI, and PM10 was associated with both DAS28 CRP and DAS28 ESR. In particular, higher PM 2.5 levels showed the strongest association with increased RA disease activity, with β coefficients (95% CIs) of 0.078 (0.020 to 0.136) for TJC28, 0.068 (0.023 to 0.112) for SJC28, 0.211 (0.069 to 0.353) for CDAI, 0.040 (0.017 to 0.064) for DAS28 CRP, 0.037 (0.013 to 0.061) for DAS28 ESR when six air pollutants were standardized to a mean of 0 and standard deviation of 1 (Table 2).

Conclusion: Elevated air pollution levels, especially PM 2.5, are associated with increased RA disease activity and flare occurrence in patients of RA.References1. Zhang RD, Chen C, Wang P, Fang Y, Jiang LQ, Fang X, et al. Air pollution exposure and auto-inflammatory and autoimmune diseases of the musculoskeletal system: a review of epidemiologic and mechanistic evidence. Environ Geochem Health. 2023;45(7):4087-105.2. Ingegnoli F, Ubiali T, Schioppo T, Longo V, Murgo A, De Lucia O, et al. Potential Short-Term Air Pollution Effects on Rheumatoid Arthritis Activity in Metropolitan Areas in the North of Italy: A Cross-Sectional Study. Int J Environ Res Public Health. 2021;18(16).

Figure 1. Longitudinal trends of monthly Air Pollutant concentrations

Table 1. Effects of Air Pollution on Flare occurrence in RA

Table 2. Effects of Air Pollution on Disease Activity in RA

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/effect-of-air-pollution-on-disease-activity-in-patients-with-rheumatoid-arthritis/