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Relation of the course of bronchial responsiveness from age 9 to age 15 to allergy
B Burrows1, M R Sears, E M Flannery
1Respiratory Sciences Center, University of Arizona College of Medicine, Tucson 85724, USA.
Insights
Bronchial hyperresponsiveness (BHR) in children decreases with age. Early BHR and allergy markers like IgE and skin tests predict later wheezing and reduced lung function, highlighting the importance of longitudinal assessment.
Area of Science:
- Pediatric Respiratory Medicine
- Allergy and Immunology
- Longitudinal Cohort Studies
Background:
- Bronchial hyperresponsiveness (BHR) is a key feature in asthma.
- Understanding the developmental trajectory and predictors of BHR is crucial for early intervention.
Purpose of the Study:
- To investigate the age-related changes in bronchial responsiveness to methacholine in a New Zealand birth cohort.
- To examine the relationship between early BHR, allergy markers, and later respiratory outcomes (wheeze, lung function).
Main Methods:
- Longitudinal assessment of bronchial responsiveness to methacholine in children from age 9 to 15.
- Measurement of serum IgE levels and allergy skin tests at specific ages.
- Correlation analysis of BHR with symptom severity and lung function parameters.
Main Results:
- Overall BHR decreased with age, but persistence of BHR was observed.
- Early BHR and allergy markers (high IgE, positive skin tests) were significantly associated with persistent BHR, increased wheezing frequency, and lower lung function at age 15.
- Children with prior BHR but unresponsive at age 15 still showed worse outcomes than those consistently unresponsive.
Conclusions:
- The tendency for BHR and its persistence are influenced by allergic sensitization.
- Allergy markers are important determinants of wheeze frequency and lung function impairment.
- A single BHR measurement may not accurately reflect an individual's overall tendency for bronchial responsiveness due to its variability over time.
Abstract:
Bronchial responsiveness to methacholine was measured in a birth cohort of New Zealand children at ages 9, 11, 13, and 15. Overall bronchial hyperresponsiveness (BHR) decreased with age. While the response at age 9 was significantly related to responsiveness, symptom severity, and low lung function at age 15, these relationships were much closer when bronchial response levels after age 9 were taken into account. Also, among children who were unresponsive to methacholine at age 15, those with previous BHR had more frequent wheeze and lower lung function than those whose previous tests were all unresponsive. Both the overall tendency to BHR and the tendency to retain BHR were closely related to high serum IgE levels (determined at age 11) and to positive allergy skin tests (determined at age 13). These evidences of allergy, closely related to the severity and course of methacholine response, appeared to be important determinants of the frequency of wheeze and the degree 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 the overall tendency to BHR.