Longitudinal measurement of non‐specific bronchial hyperresponsiveness in non‐allergic children and adolescents

Non‐speeifie bronchial hyperresponsiveness (BHR) is intimately associated with the clinical condition recognized as asthma. BHR ean be present, however, in non‐asthmatic subjects, most notable in siblings of sthmatic subjects. What is not well understood, however, is whether inereased bronchial responsiveness, once present, persists over time. In this regard we report on our longitudinal study of BHR in non‐allergic children and adolescents. The reported subjects are part of a larger on‐going study in a selected population of asthma families, normal families, and twins. Initiated in 1972, t he subjects reported here are those who have had at least one follow‐up visit through 1990, and did not have asthma or allergic histories at either their initial or follow‐up(s). Subjects completed a standardized respiratory questionnaire, had skin tests, a serum IgE level and a determination of non‐specific BHR using a methacholine challenge. Subjects were 6 to 21 years at initial visit. Non‐allergic subjects trom asthma families (n = 25), twins (n = 37), and normal families (n = 28) were followed longitudinally, and their age at subsequent visits was not restricted. In this study, we found subjects from asthma families and twins had significantly increased BHR when compared to subjects from normal families. This increased BHR persisted over time and was not influenced by the atopic status of the studied subjects.