Bronchial hyperresponsiveness in adolescents with long-term asthma remission: Importance of a family history of bronchial hyperresponsiveness

Background: The mechanisms responsible for bronchial hyperresponsiveness (BHR) in symptomatic asthma include genetic predisposition and airway inflammation, but the causes of BHR in adolescents with asthma remission are poorly understood. It has been shown that BHR in adolescents with asthma remission was not reduced by prolonged treatment with inhaled corticosteroids, in contrast to the BHR of symptomatic asthma. Objective: The aim of this study was to investigate whether family history of BHR may contribute to the persistence of BHR in asthma remission during adolescence. Methods: One hundred twenty-six adolescents with long-term asthma remission (neither symptoms nor any medication used during the previous 2 years) and their parents underwent a methacholine inhalation test. The provocative concentration of methacholine causing a 20% fall in FEV₁ (PC₂₀) and the bronchial responsiveness (BR) index were calculated for each individual. Results: Sixty-nine adolescents (54.8%) were found to have persisting BHR (PC ₂₀ < 18 mg/mL). The frequency of BHR and the BR index were significantly higher in parents (n = 138) of the BHR-persisting group (28.3% and 1,150 ± 0.103, respectively [mean ± 1 SD]) than in parents (n = 114) of BHR-nonpersisting group (16.7% [p = 0.030] and 1.124 ± 0.088 [p = 0.029], respectively). Furthermore, adolescents (n = 56) with at least one BHR-positive parent were found to have a higher frequency of BHR (66.1% vs 45.7%, p = 0.023) and a higher BR index (1.244 ± 0.090 vs 1.204 ± 0.082, p = 0.011) than adolescents (n = 70) with non-BHR parents. Conclusion: Our results suggest that adolescents in asthma remission are more likely to have BHR when there is a family history of BHR. Further studies are needed to examine the possible involvement of genetic factors in the BHR of adolescents in asthma remission.