Asthmatic symptoms often start during early childhood. Impulse oscillometry (IOS) is feasible in preschool children who may be unable to reliably perform spirometry measurements.
We evaluated the utility of IOS in a multicenter multiethnic high-risk asthma cohort entitled the Vitamin D Antenatal Asthma Reduction Trial (VDAART).
The VDAART recruited pregnant women whose children were followed from birth to age 8 years. Lung function was assessed with IOS at ages 4, 5, and 6 years and spirometry at ages 5, 6, 7, and 8 years. Asthma status, respiratory symptoms, and medication use were assessed with repeated questionnaires from birth to age 8 years.
In total 220 children were included in this secondary analysis. Recent respiratory symptoms and short-acting β2-agonist (SABA) use were associated with increased respiratory resistance at 5 Hz (R5) at age 4 years (β 2.6; 95% CI 1.0, 4.4; P=0.002 and β 3.4; 95% CI 0.7, 6.2; P=0.015, respectively). Increased R5 at age 4 years was also associated with decreased lung function from ages 5 to 8 years (β -0.3; 95% CI -0.5, -0.1; P<0.001 for FEV at 8 years) and active asthma at age 8 years (β 2.0; 95% CI 0.2, 3.8; P=0.029).
Increased respiratory resistance in preschool IOS is associated with frequent respiratory symptoms as well as school-age asthma and lung function impairment. Our findings suggest that IOS may serve as a potential objective measure for early identification of children who are at high risk of respiratory morbidity.

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