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Outcome in adulthood of asymptomatic airway hyperresponsiveness in childhood: a longitudinal population study
Finn Rasmussen1, D Robin Taylor, Erin M Flannery
1Firestone Institute for Respiratory Health, St. Joseph's Healthcare and McMaster University, Hamilton, Ontario, Canada.
Insights
Asymptomatic children with airway hyperresponsiveness (AHR) are more prone to developing asthma and atopy. Persistent AHR, even without early symptoms, significantly increases the risk of developing asthma later in life.
Area of Science:
- Pediatric Pulmonology
- Allergy and Immunology
- Epidemiology
Background:
- The long-term clinical significance of childhood-onset asymptomatic airway hyperresponsiveness (AHR) is not well-established.
- Conflicting reports exist regarding the outcomes of AHR first detected in childhood.
Purpose of the Study:
- To investigate the clinical outcomes of asymptomatic AHR identified in childhood.
- To determine the association between persistent versus transient AHR and the development of asthma and atopy.
Main Methods:
- A birth cohort of 1,037 children was followed until age 26 years.
- Airway hyperresponsiveness to methacholine was assessed at age 9 years in asymptomatic children.
- Subsequent assessments evaluated asthma symptoms, atopy markers (IgE, eosinophils, skin prick tests), and persistent AHR.
Main Results:
- Of asymptomatic 9-year-olds, 7.5% exhibited AHR.
- Children with asymptomatic AHR at age 9 were more likely to develop asthma, wheeze, and atopy later in life.
- Persistent AHR was associated with a significantly higher risk of developing asthma compared to transient AHR.
Conclusions:
- Asymptomatic childhood AHR is a risk factor for developing asthma and atopy.
- Persistent AHR should be viewed as a pathological process potentially leading to asthma, not just a marker.
- Early identification and monitoring of AHR may be crucial for predicting and potentially preventing later asthma development.
Abstract:
The clinical outcome of asymptomatic airway hyperresponsiveness (AHR) first detected in childhood is sparsely reported, with conflicting results. We used a birth cohort of 1,037 children followed to age 26 years to assess the clinical outcome of asymptomatic AHR to methacholine first documented in study members at age 9 years. Of 547 study members who denied wheezing symptoms ever at age 9 years, 41 (7.5%) showed AHR. Forty showed methacholine responsiveness, with a provocation concentration of methacholine that elicited a 20% drop in forced expired volume in 1 sec (PC(20)) < or = 8 mg/mL, and one had baseline airway obstruction with a bronchodilator response exceeding 10%. Of these 41 study members, 18 (44%), 11 (27%), and 4 (10%) maintained AHR in 1, 2, and 3 later assessments, respectively, while 23 (56%) manifested AHR only at age 9. Compared with asymptomatic study members without AHR, those with asymptomatic AHR at age 9 years were more likely to report asthma and wheeze at any subsequent assessment, were more likely to have high IgE levels and eosinophils at ages 11 and 21, and more often demonstrated positive responses to skin allergen testing at ages 13 and 21 years. Persistent AHR at later assessments increased these likelihoods further.In conclusion, asymptomatic children with AHR are more likely to develop asthma and atopy later in life compared with asymptomatic children without AHR. Persistent AHR, even though initially asymptomatic, was associated with an even greater increased risk of development of asthma. We suggest that rather than considering AHR as a marker of asthma, it should be regarded as a parallel pathological process that may lead to subsequent symptoms and clinical evidence of asthma.