Association between air pollution and health outcomes in patients with IPF: A nationwide multicenter cohort study

Air pollution has been linked to the progression of idiopathic pulmonary fibrosis (IPF). However, studies in high-pollution areas examining a wide range of clinical outcomes remain limited. We aimed to investigate the association between individual air pollution exposure and health outcomes in a nationwide IPF cohort. This study included 1233 patients (mean age: 67.1 years, male: 76.3%) with IPF from 23 medical institutions. Individual exposure to nitrogen dioxide (NO₂) and particulate matter ≤10 μm (PM₁₀) was estimated from residential addresses using a national prediction model. Cox proportional hazards regression models analysed the association between air pollutant levels and mortality, acute exacerbation (AE), and disease progression (DP, defined as a relative 10% decline in forced vital capacity). Among 1233 patients, 60.7% died, 37.1% experienced AE, and 58.5% showed DP during a median follow-up of 63 months. In the primary model, adjusted for individual- and area-level covariates, each 10 parts per billion increase in NO₂ was linked to a 16.1% increased risk of mortality (hazard ratio [HR]: 1.161; 95% confidence interval [CI]: 1.000-1.331, p = 0.043) in patients with IPF. NO₂ exposure also tended toward association with DP (HR: 1.184; 95% CI: 0.990-1.438, p = 0.071). PM₁₀ exposure was significantly associated with time to the first occurrence AE (HR: 1.172; 95% CI: 1.020-1.344, p = 0.028) and showed a marginal association with AE frequency (incidence risk ratio: 1.149; 95% CI: 0.990-1.318, p = 0.059) in patients with IPF. Our data suggested that individual-level air pollution exposure may influence long-term clinical outcomes in patients with IPF.