Long-term exposure to air pollution and prognosis of idiopathic pulmonary fibrosis

Abstract

BACKGROUND AND AIM: Short-term exposure to ambient air pollution has been associated with the prognosis of idiopathic pulmonary fibrosis (IPF). However, few studies have investigated the association of long-term exposure. This study aimed to investigate the association between long-term exposure to PM10, PM2.5, and NO2 and the prognosis of IPF including hospital admission, disease progression (DP), and mortality. METHODS: Our study population included 225 IPF patients, as a subset of a national multicenter prospective cohort of IPF in South Korea. We assessed individual long-term exposure as the annual average concentration of PM10, PM2.5, and NO2 in 2015 at geocoded home addresses of cohort participants. The prognosis was defined as hospitalization, DP ( 10% of lung function decline), or death that occurred after IPF diagnosis. We applied Cox’s proportional hazard model to estimate the hazard ratio(HR)s and 95% confidence interval(CI)s for IPF prognosis per 10 μg/m3 increase in PM10 and PM2.5, and 10 ppb increase in NO2 after adjusting for the individual- and area-level characteristics. RESULTS:HRs were mostly greater than 1 with some variation depending on the air pollutant and IPF prognosis, although all estimates were statistically insignificant possibly because of our limited sample size. For PM10, HRs of hospital admission, DP, and mortality were 1.78 (95% CI=0.68-4.67), 1.25 (0.54-2.93), and 1.15 (0.50-2.63), respectively. PM2.5 gave a positive estimate only for DP (HR=6.30, 95% CI=0.94-42.29), while NO2 showed only for mortality (1.09, 0.67-1.78). CONCLUSIONS:Our pilot study provided suggestive evidence that long-term exposure to air pollution is associated with a poor prognosis of IPF. We plan to expand our study population to the full cohort and to re-examine the association. KEYWORDS: Long-term exposure, air pollution, IPF, cohort study, prognosis