Children with Asthma Have Fixed Airway Obstruction through Childhood Unaffected by Exacerbations.

ABSTRACT

BACKGROUND: Children with asthma may have a disease course with or without exacerbations, but the relationship between exacerbations and lung function development is poorly understood. OBJECTIVE: To compare lung function trajectories from birth till adolescence in asthmatic children with and without exacerbations. METHODS: Children with asthma from the Copenhagen Prospective Studies on Asthma in Childhood2000 (COPSAC2000) birth cohort had lung function and bronchial reactivity assessed repeatedly from 1 month to 13 years. Exacerbations were diagnosed at the COPSAC clinic defined as symptoms requiring hospitalization, oral or high-dose inhaled corticosteroid treatment. Mixed models were applied to analyze lung function trajectories. RESULTS: Children with asthma with exacerbations (N = 50) had a trajectory of increased, fixed airway obstruction compared with children without exacerbations (N = 47) z-score difference in airway resistance (sRawz) (95% confidence interval [CI]) +0.34 (+0.03; +0.66), P = .03, and maximal mid-expiratory flow (MMEFz) -0.41 (-0.69; -0.13), P = .004, but no differences in forced expiratory volume (FEVz) -0.14 (-0.41; +0.13), P = .29, or bronchial reactivity to methacholine (PDz) +0.08 (-0.26; +0.42), P = .65. This did not change comparing lung function trajectories before and after exacerbations z-score difference (95% CI) sRawz -0.04 (-0.35; 0.27), P = .80; MMEFz 0.01 (-0.02; 0.04), P = .55; FEVz 0.02 (-0.02; 0.05), P = .42; and PDz -0.01 (-0.06; 0.05), P = .88. CONCLUSION: Children with asthma with exacerbations compared with children with asthma without exacerbations are characterized by increased airway obstruction since infancy through childhood. The airway obstruction is a fixed trajectory without progression due to exacerbations, suggesting that exacerbations are a consequence rather than a cause of diminished airway caliber in childhood.