Asymptomatic bronchial hyperresponsiveness in adolescents and young adults

The clinical significance of asymptomatic bronchial hyperresponsiveness (BHR) is not well-known. The aim of this study was to explore, in a cross-sectional analysis, the characteristics of adolescent subjects with asymptomatic BHR, as compared to nonhyperresponsive subjects and those with symptomatic BHR. The subjects were selected by date of birth from the register of general practitioners. The hypothesis that both asymptomatic and symptomatic BHR are related to early childhood lower respiratory tract infections was also tested, in a historical cohort analysis. Respiratory morbidity was studied in early childhood and BHR in adolescence and young adulthood, in a population of 551 subjects aged 10-23 yrs. Morbidity had been recorded prospectively since birth in the general practice. Data on chronic respiratory symptoms, smoking behaviour, airways obstruction, BHR and allergy were collected during this investigation. BHR was present in 42% of the subjects, of which 70% were asymptomatic. The occurrence of symptomatic BHR was related to acute bronchitis in early childhood, allergy, airways obstruction and recent asthma, acute bronchitis and hay fever; whereas, asymptomatic BHR was not. Characteristics of subjects with asymptomatic BHR did not differ significantly from those without BHR, with respect to these factors. We conclude that asymptomatic bronchial hyperresponsiveness in adolescence and young adulthood is not related to lower respiratory infections in early childhood. Furthermore, subjects with asymptomatic bronchial hyperresponsiveness have similar characteristics to those without bronchial hyperresponsiveness, but differ strongly from subjects with symptomatic hyperresponsiveness. Asymptomatic bronchial hyperresponsiveness may not be the link between early childhood lower respiratory morbidity and asthma in later life, nor a risk factor for later asthma.