Nitrogen dioxide exposure ups risk of IPF progression

Patients with idiopathic pulmonary fibrosis (IPF) who have high exposure to nitrogen dioxide (NO₂) are at greater risk of disease progression, suggests a recent study.

A team of investigators explored the effect of individual exposure to NO₂ and particulate matter (aerodynamic diameter ≤ 10 μm [PM₁₀]) on disease progression by analysing the serial lung function data of 946 IPF patients (mean age 65.4 years, 80.9 percent male).

Using a national-scale exposure prediction model, the investigators estimated individual-level long-term exposures to NO₂ and PM₁₀ at the residential addresses of patients. The model was constructed using air quality regulatory monitoring data.

Disease progression was characterized by a relative decline (≥10 percent) in forced vital capacity. The investigators adjusted individual- and area-level covariates in the primary analysis model.

Over a median follow-up of 1.0 year, 547 patients (57.8 percent) had disease progression. In the primary model, a 10-ppb increase in NO₂ concentration resulted in a 10.5-percent increase in the risk of progression (hazard ratio [HR], 1.105, 95 percent confidence interval [CI], 1.000‒1.219) in IPF patients.

A rising trend of progression was also observed in this population, according to the second to fourth quartiles of NO₂ (Q2: HR, 1.299, 95 percent CI, 0.972‒1.735; Q3: HR, 1.409, 95 percent CI, 1.001‒1.984; Q4: HR, 1.598, 95 percent CI, 1.106‒2.310) relative to the first quartile.

On the other hand, no significant association was noted between PM₁₀ and progression in IPF patients.

“Air pollution affects clinical course and prognosis of IPF,” the investigators said.