Bronchodilation and bronchoconstriction: Predictors of future lung function in childhood asthma

Background: Persistently low levels of lung function are associated with subsequent symptoms in patients with asthma as children. Objectives: We hypothesized that objective measures of baseline pulmonary function would be independently associated with future lung function in the Childhood Asthma Management Program and that these associations might vary with treatment. Methods: We evaluated the association of FEV ₁, airway responsiveness, and bronchodilator response at randomization as predictors of longitudinal growth in FEV ₁ at the 48-month follow-up visit in the 1041 Childhood Asthma Management Program participants. Results: Baseline levels of airway responsiveness and bronchodilator response were significantly associated with baseline level of lung function. In multivariate models, higher bronchodilator response (β = 0.22; P < .0001), log PC ₂₀ (β = 1.82; P < .0001), and FEV ₁ (β = 0.58; P < .0001) at randomization were each associated with higher levels of prebronchodilator FEV ₁, as a percent of predicted, after 4 years. Similar associations were noted for prebronchodilator forced vital capacity and FEV ₁/forced vital capacity ratio. Baseline bronchodilator response was a particularly powerful predictor of lung function improvements while on inhaled corticosteroids, whereas airway responsiveness was a better predictor in subjects not randomized to any controller medications. Conclusion: We conclude that baseline bronchodilator response, airway responsiveness, and level of FEV ₁ are independent predictors of subsequent level of FEV ₁ in childhood asthma and may have treatment-specific prognostic significance for persistence of symptoms into early adulthood. Clinical implications: In asthma, bronchodilator and bronchoconstrictor responses are independent predictors of future lung function and should not be used interchangeably; bronchodilator response may indicate good response to inhaled corticosteroids.