Association between inhaled corticosteroids and incidence of idiopathic pulmonary fibrosis: nationwide population-based study.

Background: Idiopathic pulmonary fibrosis (IPF) is a progressive disease found primarily in older people, with the use of systemic steroids linked to poor outcomes. However, the role of inhaled corticosteroids (ICSs) in IPF remains unclear. This study investigated the association between ICS use and IPF risk using national insurance data, particularly in individuals with chronic airway diseases.

Methods: Using the National Health Insurance Service-National Sample Cohort database, our study included patients diagnosed with chronic obstructive pulmonary disease or asthma. ICS exposure was assessed via treatment claims, and IPF cases were identified using broad and narrow criteria. We used inverse probability of treatment weighting (IPTW) with propensity scores for balanced covariate analysis.

Results: Of 57 456 patients (mean age: 55.9 years, 42.3% men), 16.5% used ICS and 83.5% did not. ICS users showed higher rates of broad (0.98 vs 0.41 per 1000) and narrow IPF (0.61 vs 0.21 per 1000) than non-users. Pre-IPTW, ICS use was associated with increased IPF risk; however, this was not significant post-IPTW. Post-IPTW, both ICS dose as a continuous variable (broad adjusted HR per 100 µg/day: 1.03, 95% CI: 1.02 to 1.04; narrow adjusted HR per 100 µg/day: 1.03, 95% CI: 1.01 to 1.04 post-IPTW) and high-dose ICS (≥1000 µg/day) (broad adjusted HR: 3.89, 95% CI: 1.61 to 9.41; narrow adjusted HR: 3.99, 95% CI: 1.19 to 13.41) use correlated with an elevated IPF risk.

Conclusion: While no overall significant association between ICS use and IPF risk was observed post-IPTW, there may be an increased risk in patients using high-dose ICS.