Fine particles matter components and interstitial lung disease in rheumatoid arthritis

Abstract

Exposure to ambient fine particulate matter (PM_2.5) is a risk factor for pulmonary and systemic autoimmune diseases, however evidence on which PM_2.5 chemical components are more harmful is still scant. Our goal is to investigate potential associations between PM_2.5 components and interstitial lung disease (ILD) onset in rheumatoid arthritis (RA).

New-onset RA subjects identified from a United States health care insurance database (MarketScan) were followed for new onset of RA associated ILD (RA-ILD) from 2011 to 2018. Annual ambient PM_2.5 concentrations of its chemical components (i.e. sulfate, nitrate, ammonium, organic matter, black carbon, mineral dust, and sea salt) were estimated by combining satellite retrievals with chemical transport modelling and refined by geographically weighted regression. Exposures from 2006 up to one year before ILD onset or end of study were assigned to subjects based on their metropolitan division or core-based statistical area codes. A novel time-to-event quantile-based g(generalised)-computation approach was used to estimate potential associations between RA-ILD onset and the exposure mixture of all seven PM_2.5 chemical components adjusting for age, sex, and prior chronic obstructive pulmonary disease (as a proxy for smoking).

We followed 280 516 new-onset RA patients and detected 2194 RA-ILD cases across 1 394 385 person-years. The adjusted hazard ratio for RA-ILD onset was 1.54 (95% confidence interval 1.47–1.63) per every decile increase in all seven exposures. Ammonium, mineral dust, and black carbon contributed more to ILD risk than the other PM_2.5 components.

In conclusion, exposure to elements of PM_2.5, particularly ammonium, increases ILD risk in RA.