Objectives: This study sought to better define the clinical characteristics of severe asthma in both children and adults, and to evaluate the effect of asthma duration on multiple parameters of disease severity.
Design: Retrospective analysis of prospectively collected data on 275 patients (125 children) with severe asthma who were admitted to a tertiary asthma referral center.
Methods: Demographics, lung function (ie, spirometry and body box plethysmography), glucocorticoid (GC) pharmacokinetic studies, and lymphocyte stimulation assays were performed on all patients.
Results: Children were as likely to require therapy with high-dose inhaled GCs and long-term therapy with oral GCs, and to have had a prior intubation, yet they had significantly less airflow limitation (mean [+/- SEM] FEV(1), 74.0 +/- 2.1% predicted vs 57.1 +/- 1.8% predicted, respectively; p < 0.0001), less resistance to airflow (mean airway resistance, 140.3 +/- 8.5% predicted vs 311 +/- 18% predicted, respectively; p < 0.0001), and larger lung volumes (mean total lung capacity, 116.4 +/- 1.6% predicted vs 105.3 +/- 1.8% predicted, respectively; p < 0.0001) compared to adults. Children were more likely to be male and to display greater responsiveness to GCs in vitro. Lung function impairment was associated with asthma duration in children and in adults with onset of asthma in childhood, while there was no relationship between disease severity and asthma duration among those with adult-onset asthma. Despite significant differences in disease duration, patients with adult-onset asthma had equally compromised lung function compared to adults with long-standing asthma.
Conclusions: Children with severe asthma tended to be male, to have less severe airflow obstruction, and to display greater responsiveness to GCs in vitro compared to adults. Symptoms and episodic acute declines in lung function may precede chronic airflow limitation in this group of children. As such, it may be more relevant to follow the deterioration in lung function over time in children. Finally, disease severity in children and adults whose onset of asthma occurred in childhood was related to disease duration, but not in patients with onset of asthma in adulthood.