TOPLINE:

Older adults with long-term exposure to fine particulate matter and certain gaseous air pollutants had an increased incidence of rheumatoid arthritis (RA). The association between higher exposure to particulate matter with diameters of ≤ 2.5 μm (PM_2.5) and increased risk for RA was stronger in those with high-risk job exposures and certain racial and ethnic groups.

METHODOLOGY:

• Researchers analyzed data from a large prospective cohort to examine whether long-term exposure to particulate matter or gaseous pollutants was associated with the occurrence of late-onset RA.
• They included 42,152 adults aged 65 years or older in California enrolled in Medicare Fee-for-Service between 2001 and 2018.
• Exposures to PM_2.5, PM₁₀, and gaseous pollutants, including nitrogen dioxide, nitrogen oxides, carbon monoxide, and ozone were estimated using satellite data and neighborhood monitoring.
• Incident RA was identified using Medicare claims, requiring at least two RA diagnoses.
• Participants were followed up until RA diagnosis, death, or the end of 2018. The average follow-up duration was 6.1 years for those who developed RA and 12.0 years for those who did not.

TAKEAWAY:

• Over the follow-up period, 2027 participants were diagnosed with RA (1479 women).
• Incidence of RA increased with increased exposures to PM_2.5 (adjusted hazard ratio [aHR] per 2 μg/m³ increase in exposure, 1.20 ; 95% CI, 1.16-1.23) and nitrogen dioxide (aHR per 10 μg/m³ ≥ increase in exposure, 1.44; 95% CI, 1.36-1.52). Exposure to PM₁₀, nitrogen oxides and carbon monoxide were also positively associated with RA risk, while ozone exposure was not.
• Participants with high-risk work exposures showed a stronger association between PM_2.5 exposure and RA incidence than those without such exposures (aHR, 1.29 vs 1.16; P for heterogeneity = .04), and this association persisted across medication-claim groups.
• Associations between PM_2.5 exposure and RA incidence were stronger in African American and Latino participants than in Japanese American or White participants.

IN PRACTICE:

“Long-term air pollution exposure is associated with late-onset RA in a multiethnic population of adults ≥ 65 years. While these findings persist across education, neighborhood socioeconomic status, distance from roads, and moving status, subgroup analyses suggest that air pollution may have greater effects in racial and ethnic minoritized groups,” the authors of the study wrote.

SOURCE:

This study was led by Anna H. Wu, PhD, University of Southern California in Los Angeles. It was published online on January 12, 2026, in Arthritis & Rheumatology.

LIMITATIONS:

Researchers lacked detailed clinical data on RA, including disease severity and blood markers. They did not account for air pollution exposure during travel or time spent indoors. The findings may not be generalizable to all patients with RA because the analyses were limited to Medicare Fee-for-Service beneficiaries.

DISCLOSURES:

This study received support from the National Cancer Institute and a pilot grant from the National Institute of Environmental Health Sciences. The authors reported having no actual or potential competing financial interests or conflicts.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.