Nonuniform growth in pediatric lung function between 4 and 14 years of age

We have previously observed that 4-year-old children with a high respiratory resistance (Rrs) exhibit the largest drop in resistance by 9 years of age. This drop is independent of airway muscle tone. Aim: to study the longitudinal change in Rrs from the preschool age up to puberty. Methods: 130 children who participate in a prospective birth-cohort in the region of Antwerp, Belgium and whose lung function had been assessed at 4 and 9 years were re-invited at 14 years of age. All children were born at term, had no doctor-diagnosis of asthma and had never used asthma medication for > 1 month. Results: 120 participating children (64 M: 56 F) were divided based on the magnitude of Rrs at 4 Hz (Rrs4) at 4 years of age. Children with high Rrs4-values at the preschool age exhibited an accelerated drop in Rrs4 from 4 to 9 years of age (see figure). However, from 9 to 14 years of age, the decrease in Rrs4 was independent of the magnitude of Rrs4, except for the group of children with the lowest Rrs4 values who exhibited less growth in lung function. Although the differences in Rrs4 in 4-year-old children disappeared to a large extent from 4 to 9 years of age, the subgroups of children still had significantly different Rrs4 values by the ages of 9 and 14 years. Conclusion: Four-year-old children with high airway resistance exhibit the largest drop in resistance by 9 years of age but this accelerated growth ceases at the school-age.