The distribution of bronchial responsiveness to histamine and exercise in 527 children and adolescents

The aim of the study was to describe the bronchial responsiveness to inhaled histamine and exercise in a randomly selected group of 527 children and adolescents from Copenhagen, aged between 7 to 16 years. The distribution of the bronchial responsiveness was described as (1) the provoking concentration that causes a 20% reduction in FEV1 (2) the dose-response slope (DRS), that is, the linear slope of the dose-response curve, and (3) reduction in FEV1 after 6 minutes of exercise on a treadmill. The distribution of the concentration that causes a 20% reduction in FEV1 in the responsive range was not significantly different from a unimodal distribution, although the findings were skewed toward the less responsive end of the range (p greater than 0.05). The subjects with asthma represented a subgroup within the responsive distribution tail rather than a separate distribution peak. In asymptomatic individuals, the values of DRS were distributed symmetrically on a logarithmic scale. The deviation from normal was such that the standard deviation only slightly underestimated the "normal" range. The distribution of the bronchial response to exercise was found to be significantly different from a normal distribution. However, a significant relationship was found between the bronchial response to inhaled histamine and exercise (p less than 0.0001). We conclude that there is a log-normal distribution of the bronchial response to inhaled histamine in a random sample of children and adolescents.