Short-term air pollution exposure and hospitalizations in idiopathic pulmonary fibrosis: data from the IPF-PRO Registry

RATIONALE: While long-term exposure to ambient air pollution in patients with idiopathic pulmonary fibrosis (IPF) has been associated with an increased risk of disease progression and mortality, the risks associated with acute exposure are less clear. OBJECTIVE: To determine whether acute exposure to fine particulate matter (PM2.5) is associated with an increased risk of respiratory hospitalization in patients with IPF. METHODS: We performed a case crossover analysis of patients with at least one respiratory hospitalization in the IPF-PRO Registry of individuals with IPF enrolled at 46 sites across the US. Acute exposure to PM2.5 was estimated as the average concentration at the regulatory air quality monitor nearest to the individual's residential address for each day in the week preceding hospitalization. Control days were selected using a time-stratified design. Conditional logistic regression estimated the association between average PM2.5 concentration for each lag day and the odds of respiratory hospitalization, adjusting for time-varying confounders. RESULTS: In adjusted conditional logistic analyses, each 5µg/m3 higher PM2.5 on lag day 0 was associated with a 22% (95% confidence interval, 14% to 47%) higher odds of respiratory-related hospitalization. No significant association was observed for PM2.5 in the other days in the week preceding the hospitalization. There was no significant effect modification by age, sex, Social Vulnerability Index, MUC5B allele status, telomere length, or antifibrotic drug use. CONCLUSION: Increased exposure to PM2.5 is associated with an increased risk of same-day hospitalization in individuals with IPF, suggesting that efforts to reduce community and individual exposure to air pollutants may improve patient outcomes. CLINICAL TRIAL REGISTRATION: Clinical trial registered with www.clinicaltrials.gov (NCT01915511). PRIMARY SOURCE OF FUNDING: The IPF-PRO Registry is supported by Boehringer Ingelheim Pharmaceuticals, Inc and run in collaboration with the Duke Clinical Research Institute and enrolling centers.