RELATION OF THE COURSE OF BRONCHIAL RESPONSIVENESS FROM AGE-9 TO AGE-15 TO ALLERGY

Bronchial responsiveness to methacholine was measured in a birth cohor t of New Zealand children at ages 9, 11, 13, and 15. Overall bronchial hyperresponsiveness (BHR) decreased with age. While the response at a ge 9 was significantly related to responsiveness, symptom severity, an d low lung function at age 15, these relationships were much closer wh en bronchial response levels after age 9 were taken into account. Also , among children who were unresponsive to methacholine at age 15, thos e with previous BHR had more frequent wheeze and lower lung function t han those whose previous tests were ail unresponsive. Both the overall tendency to BHR and the tendency to retain BHR were closely related t o high serum IgE levels (determined at age 11) and to positive allergy skin tests (determined at age 13). These evidences of allergy, closel y related to the severity and course of methacholine response, appeare d to be important determinants of the frequency of wheeze and the degr ee of impairment of lung function at the end of follow-up. In view of the variability in BHR, a single estimate of bronchial responsiveness taken at an arbitrary point in time may not be an accurate index of th e overall tendency to BHR.