Abstract
Rationale: The clinical outcome of asymptomatic airway hyper-responsiveness (AHR) is sparsely reported and results are conflicting.
Methods: We studied a birth cohort study of 1037 New Zealand children to assess the outcome of asymptomatic AHR to methacholine, first documented at age 9. Study members were seen at intervals to age 26, completing respiratory questionnaires, together with repeated measurements of atopy and lung function.
Results: Of 547 study members who reported no wheezing symptoms ever to age 9, 41(7.5%) had asymptomatic airway hyperresponsiveness (AHR). Of these, 7 (17%), 7(17%) and 4(10%) maintained AHR in one, two or three later assessments respectively, while 23(56%) had AHR only at age 9. Study members with asymptomatic AHR at age 9 reported more asthma and wheeze at later assessments, had higher IgE levels and more eosinophils at ages 11 and 21, and more atopy by skin test at age 21, compared with asymptomatic study members without AHR. Persistent AHR at several assessments increased the likelihood of these outcomes.
Conclusions: Asymptomatic children with AHR develop more asthma and atopy in adolescence and young adulthood than asymptomatic children without AHR. The persistence of AHR on multiple assessments increased the risk of developing asthma. Although AHR is considered a marker of asthma, it may reflect a parallel pathological process that leads to clinical asthma.