Airway hyperresponsiveness and symptoms of asthma in a six-year follow-up study of childhood asthma

Background and aim: In an inception cohort study of 457 asthmatic children diagnosed at the age of 3 to 4 years, airway hyperresponsiveness (AHR) was assessed 6 years after first diagnosis in a subgroup of 84 children. Our objective was to associate the level of AHR with the symptomatic asthma status at follow-up. Methods: Information on respiratory symptoms and medication use for the previous 6 years was obtained. Children with reported wheezing episodes during the previous year (n = 169) or for greater than or equal to 2 years at any time during the follow-up period (n = 85) were eligible fbr the challenge test. Results: Among the 254 eligible children, 166 were randomly selected. The parents of 88 of them consented to have their child participate. At the time of assessment of AHR, 19 children (22%) were asymptomatic and 24 others (29%) had symptoms but did not use any medication, Forty-one children (49%) were symptomatic and required medication, including antiinflammatory preparations in 26 instances (31%). All but two children had significant AHR. There was no significant association between the level of AHR and graded symptomatic and medication score, Twenty-four of the 70 children (34%) with greatly enhanced AHR used no medication. Conclusions: This study shows that (1) almost all children first diagnosed with asthma 6 years ago and with persisting but not necessarily current symptoms of asthma have increased AHR, which satisfies a proposed epidemiologic definition of asthma; (2) AHR was present in 95% of the 20 currently asymptomatic children; and (3) one third of children with greatly enhanced AHR did not use any treatment.