Air pollution linked to spikes in rheumatoid arthritis activity and flare risk

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A novel study in the Annals of the Rheumatic Diseases shows that exposure to air pollution, especially fine particulate matter, is associated with increased disease activity and flare risk in rheumatoid arthritis (RA). The findings underscore the importance for healthcare providers and policy makers to recognize the impact of air pollution on the management of RA. Credit: Sun Hwan Shim

A study shows that exposure to air pollution, especially fine particulate matter like dust, soot and smoke (PM2.5), is associated with increased disease activity and flare risk in rheumatoid arthritis (RA).

The findings from an article in the journal Annals of the Rheumatic Diseases (ARD) underscore the importance of health care providers and policymakers recognizing its impact on RA management.

RA is a chronic autoimmune disease characterized by joint inflammation and damage, and widespread systemic symptoms can affect other parts of the body beyond the joints. Globally, it affects about 0.5% to 1% of the adult population. Many factors contribute to the development of RA, such as genetics, immune system changes and environmental exposures. These environmental factors may play a critical role in both the onset and exacerbation of RA; importantly, many are modifiable. Smoking is one of the well-established risk factors, while climatic factors, such as air temperature and humidity, and certain pollutants, like silica, have also been implicated.

Previous epidemiological studies have shown an association between air pollution and an increased risk of developing RA. A team of investigators in South Korea 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.

Editorial sees broad implications

In an accompanying editorial, Jeffrey A. Sparks, M.D., M.M.Sc., of the Division of Rheumatology, Inflammation, and Immunity at 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, biological 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 poor-quality air and provide some potential explanation for otherwise idiosyncratic RA flares."

Tracking pollution against clinic visits

This prospective cohort study tracked 1,070 patients with RA 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; particulate matter with a diameter of 10 µm, PM10; and particulate 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 a sensitivity analysis to better control for time-invariant confounding and avoid potential reverse causation inherent in the monthly analysis, investigators applied a case-crossover design using daily air pollutant concentrations preceding each visit. They used conditional logistic regression to assess changes within the same patient.

Fine particles stood out

"Our study found that higher PM2.5 concentrations were associated with increased disease activity and flare risk, particularly with prolonged exposure to elevated PM2.5 over more than two weeks," explains lead investigator Eun Bong Lee, M.D., Ph.D., of the 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.

The investigators identified PM2.5 as the key contributor to increased RA disease activity. Because these microscopic particles are smaller than red blood cells, they can easily travel from the lungs into the bloodstream, circulating to distant organs. They can then trigger the overproduction of harmful molecules called reactive oxygen species, thereby inducing cellular stress, damaging DNA and sparking inflammatory responses in organs.

Questions beyond one population

Lee concludes, "Our study has important implications for public health policymaking. While further studies are warranted to determine whether improving air quality can reduce disease activity in RA patients, we recommend that these patients avoid prolonged exposure to poor air quality, particularly high PM2.5 levels."

ARD Editor-in-Chief Josef Smolen, M.D., of the Medical University of Vienna, adds, "As always, this paper underwent thorough peer review, and it was nice to learn that all reviewers agreed on the importance and interest of these findings. Nevertheless, we should be aware that the observations pertain to the studied Korean population, with a specific genetic background and under specific environmental circumstances.

Whether these data hold true in other regions of the world should be a focus of future investigations. However, it is an excellent starting point for our better understanding of factors that may play a role in influencing disease activity and therapeutic responses of patients with RA. And it is an important wake-up call. The environment is likely an essential contributor to pain and inflammation in the patients for whom we care."

Publication details

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

Journal information: Annals of the Rheumatic Diseases

Key medical concepts

Rheumatoid ArthritisReactive Oxygen Species

Clinical categories

RheumatologyCommon illnesses & Prevention Provided by Elsevier Who's behind this story?

Swati Mestri

Swati Mestri holds a bachelor's degree in Electronics Engineering and has worked as a content editor since 2019. She has experience editing research documents across technology, health care, and materials science, and has a particular interest in technology and space. Full profile →

Robert Egan

Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →

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