Specific airway resistance in 3-year-old children: a prospective cohort study

Summary Background The development of a method to assess lung function in young children may provide new insight into asthma development. Plethysmographic measurement of specific airway resistance (sR aw ) is feasible in this age group. We aimed to identify risk factors associated with low lung function in early childhood in a prospective birth cohort. Methods Children were prenatally assigned to risk group according to parental atopic status (high risk, both parents atopic; medium risk, one parent atopic; low risk, neither parent atopic) and followed prospectively until age 3 years. We measured sR aw in 503 symptom-free children using whole-body plethysmography during tidal breathing. Findings 803 of 868 children attended the clinic, of whom 503 obtained satisfactory sR aw readings. 200 who wheezed at least once during first 3 years of life had significantly higher sR aw than the 303 who had never wheezed (mean difference 5·8%, 95% CI 2·2–9·3, p=0·002). For children who had never wheezed there were significant differences in sR aw between risk groups (p aw (geometric mean 1·17 kPa/s, 1·12–1·22) than children at medium risk (n=162; 1·02 kPa/s, 1·00–1·05) and at low risk (54; 1·04 kPa/s, 0·99–1·11). Atopic children (n=62) had significantly higher sR aw (1·15 kPa/s, 1·09–1·21) than those who were not atopic (232; 1·05 kPa/s, 1·02–1·07, p=0·002). For non-atopic children, those at high risk (58) had higher sR aw (1·13 kPa/s, 1·07–1·18) than those at medium risk (125, 1·01 kPa/s, 0·98–1·05) or at low risk (49, 1·04 kPa/s, 0·97–1·10, p=0·003). We showed a significant interaction between history of maternal asthma and child's atopic status (p=0·006). Interpretation Even in the absence of respiratory symptoms, children of atopic parents and those with personal atopy have impaired lung function in early life.