Dirty Air May Trigger Painful Rheumatoid Arthritis Flares

A new study has found that exposure to dirty air can trigger painful rheumatoid arthritis (RA) flares, making the condition more active and increasing the likelihood of flare-ups. The study, published in the Annals of the Rheumatic Diseases, investigated the effects of air pollution on disease activity in patients with RA and found that fine particulate matter (PM2.5) was the main contributor to increased RA activity.

Rheumatoid arthritis is a chronic autoimmune condition that causes inflammation and damage in the joints, as well as widespread symptoms that affect other areas of the body. The disease affects an estimated 0.5% to 1% of adults worldwide, with its development influenced by a combination of genetics, changes in immune function, and environmental exposures.

Previous studies have found that exposure to polluted air was associated with a greater likelihood of developing RA. However, this new study aimed to determine whether air pollution could also affect disease activity and trigger flares in people who already had the condition. The researchers in South Korea wanted to investigate the biological processes that might explain such a connection.

The study followed 1,070 people with RA at a major medical center in South Korea over a four-year period (2021-2024). During this time, the researchers collected information from 12,583 outpatient visits conducted under real-world clinical conditions. To estimate each patient’s exposure, the team examined monthly levels of six common air pollutants, including sulfur dioxide, nitrogen dioxide, ozone, carbon monoxide, particulate matter with a diameter of 10 µm (PM10), and particulate matter with a diameter of 2.5 µm (PM2.5).

The analysis accounted for a wide range of factors that could influence the results, including patient demographics, serologic status, medication use, socioeconomic conditions, and weather-related variables. The researchers also performed a sensitivity analysis designed to reduce the influence of factors that remained constant over time and to limit the possibility that disease activity itself affected the pollution measurements used in the monthly analysis.

The 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. Among the pollutants studied, PM2.5 appeared to be the main contributor associated with increased RA activity. The researchers suggest that these particles may stimulate excessive production of reactive oxygen species, which are harmful molecules that can place cells under stress, potentially contributing to greater RA activity and more frequent flares.

Dr. Eun Bong Lee, lead investigator of the study, emphasizes the importance of public health policy making in addressing the issue of air pollution and its effects on RA patients. ‘Our study has important implications for public health policy making. While further studies are warranted to determine whether improving air quality can reduce disease activity in RA patients, we would recommend these patients avoid prolonged exposure to poor air quality, particularly high PM2.5 levels,’ Dr. Lee says.

The researchers emphasize that additional studies are needed to determine whether reducing pollution exposure or improving air quality can directly lower disease activity in people with RA. However, the results suggest that limiting prolonged exposure during periods of poor air quality may be a practical precaution for RA patients.