Nitrogen dioxide increases the risk of mortality in idiopathic pulmonary fibrosis
Hee-Young Yoon, Sun-Young Kim, Ok-Jin Kim, Jin Woo Song
European Respiratory Journal 2021 57: 2001877; DOI: 10.1183/13993003.01877-2020
Ambient air pollution is associated with the prognosis of idiopathic pulmonary fibrosis (IPF) patients. We aimed to identify the impacts of individual exposure to particulate matter with a 50% cut-off aerodynamic diameter of 10 μm (PM10) and nitrogen dioxide (NO2) on IPF patients' mortality.
1114 patients (mean age 65.7 years; male 80.5%) diagnosed with IPF between 1995 and 2016 were included in this study. Individual-level long-term concentrations of PM10 and NO2 at residential addresses of patients were estimated using a national-scale exposure prediction model. The effect of PM10 and NO2 on mortality was estimated using a Cox proportional hazards model adjusted for individual- and area-level covariates.
The median follow-up period was 3.8 years and 69.5% of the patients died or underwent lung transplantation. When adjusted for individual- and area-level covariates, a 10 ppb increase in NO2 concentration was associated with a 17% increase in mortality (hazard ratio (HR) 1.172, 95% CI 1.030–1.344; p=0.016). When IPF patients were stratified by age (≥65 versus <65 years) or by sex, NO2 was a significant prognostic factor for mortality in the elderly (HR 1.331, 95% CI 1.010–1.598; p=0.010). When stratified by age and sex jointly, NO2 showed the stronger association with mortality in elderly males (HR 1.305, 95% CI 1.072–1.598; p=0.008) than in other groups. PM10 was not associated with IPF mortality in all patients and in subgroups stratified by age or sex.
Our findings suggest that increased exposure to NO2 can increase the risk of mortality in patients with IPF, specifically in elderly males.
Exposure to nitrogen dioxide is associated with increased risk of mortality in patients with idiopathic pulmonary fibrosis, particularly in elderly males https://bit.ly/35dopLn
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Author contributions: J.W. Song takes full responsibility for the content of this manuscript, including the data and analyses. J.W. Song made substantial contributions to the concept and design of the study. S-Y. Kim developed the design of the methodology. H-Y. Yoon, S-Y. Kim, O-J. Kim and J.W. Song made substantial contributions to the analysis and interpretation of data. H-Y. Yoon, S-Y. Kim and J.W. Song drafted the initial manuscript. All authors discussed the results and reviewed the manuscript.
Conflict of interest: H-Y. Yoon has nothing to disclose.
Conflict of interest: S-Y. Kim has nothing to disclose.
Conflict of interest: O-J. Kim has nothing to disclose.
Conflict of interest: J.W. Song has nothing to disclose.
Support statement: This study was supported by a grant from the Basic Science Research Program through the National Research Foundation of Korea, which is funded by the Ministry of Science and Technology (NRF-2019R1A2C2008541 and NRF-2018R1A2B6004608), a grant (2020IL0036) from the Asan Institute for Life Sciences, Asan Medical Center, Seoul, Korea, and a grant (NCC-1810220-01) from the National Cancer Center, Korea. Funding information for this article has been deposited with the Crossref Funder Registry.
- Received May 20, 2020.
- Accepted November 3, 2020.