Children with asthma have reduced lung function. This study addresses the question: Are they born that way?

Prospective birth cohort of 411 children from Denmark whose mothers had a physician’s diagnosis of asthma.

At age 1 month, subjects’ spirometric and bronchial responsiveness to methacholine was obtained by thoracic compression technique. At age 7 years, subjects’ lung function was measured by using spirometry. Asthma was diagnosed prospectively, from daily diary cards and clinic visits every 6 months, if the following were noted: recurrent episodes of troublesome lung symptoms typical of asthma, need for rescue use of inhaled β2-agonist, and response to inhaled corticosteroids.

Children with asthma by age 7 years (14%) already had a significant airflow deficit as neonates (forced expiratory flow at 50% reduced by 0.34, z score, P = .03), which progressed (0.82 z score, P < .0001) by age 7 years, suggesting that ∼40% of the...

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