Relationship between Inhaled Corticosteroid Therapy and Rate of Lung Function Decline in Children with Cystic Fibrosis

Objective: To assess the relationship between inhaled corticosteroids (ICS) use and lung function decline in children with cystic fibrosis (CF) using the Epidemiologic Study of Cystic Fibrosis, an observational study of patients with CF in North America. Study design: We analyzed data from 2978 patients 6 to 17 years old enrolled in ESCF between 1994 to 2004. We estimated the rate of decline in forced expiratory volume in 1 second (FEV₁) before and after starting ICS therapy with a piecewise linear continuous single change point model, adjusting for potentially confounding covariates. Results: Before initiation of ICS, mean FEV₁ decline was -1.52% predicted/year (95% CI: -1.96 to -1.08% predicted/year). After initiation of ICS therapy, mean FEV₁ decline was -0.44% predicted/year (95% CI: -0.85 to -0.03% predicted/year), which was a significant change (P = .002). ICS use was associated with decreased height for age Z scores and increased insulin/oral hypoglycemic use. Conclusions: In this retrospective analysis of prospectively collected data, ICS therapy in patients with CF was associated with a significant reduction in the rate of FEV₁ decline, decreased linear growth, and increased insulin/oral hypoglycemic use.