The clinical outcome of asymptomatic
airway hyperresponsiveness (AHR) first detected in childhood is sparsely reported, with conflicting results. We used a birth cohort of 1,037 children followed to age 26 years to assess the clinical outcome of asymptomatic AHR to
methacholine first documented in study members at age 9 years. Of 547 study members who denied
wheezing symptoms ever at age 9 years, 41 (7.5%) showed AHR. Forty showed
methacholine responsiveness, with a provocation concentration of
methacholine that elicited a 20% drop in forced expired volume in 1 sec (PC(20)) < or = 8 mg/mL, and one had baseline
airway obstruction with a
bronchodilator response exceeding 10%. Of these 41 study members, 18 (44%), 11 (27%), and 4 (10%) maintained AHR in 1, 2, and 3 later assessments, respectively, while 23 (56%) manifested AHR only at age 9. Compared with asymptomatic study members without AHR, those with asymptomatic AHR at age 9 years were more likely to report
asthma and wheeze at any subsequent assessment, were more likely to have high
IgE levels and eosinophils at ages 11 and 21, and more often demonstrated positive responses to skin
allergen testing at ages 13 and 21 years. Persistent AHR at later assessments increased these likelihoods further.In conclusion, asymptomatic children with AHR are more likely to develop
asthma and atopy later in life compared with asymptomatic children without AHR. Persistent AHR, even though initially asymptomatic, was associated with an even greater increased risk of development of
asthma. We suggest that rather than considering AHR as a marker of
asthma, it should be regarded as a parallel pathological process that may lead to subsequent symptoms and clinical evidence of
asthma.