Abstract

Background: Early childhood asthma is known to leave a persistent mark in the lung function. Impulse oscillometry (IOS) is a feasible method for evaluating lung function even in preschoolers. We studied whether preschool lung function assessed with IOS is associated with asthma in adolescence.

Methods: During years 2002-2004 lung function of 255 children aged 4-7 years was tested by using IOS. Baseline measurements were followed by exercise challenge and bronchodilatation tests. For baseline lung function, z-scores were calculated by using age and height specific predicted values. Exercise-induced bronchoconstriction was defined as a ≥35 % increase in respiratory resistance at 5 Hz (Rrs5) after the running test. Bronchodilation test was regarded significant with a ≥35 % decrease in Rrs5 after the salbutamol inhalation.

121 children participated in the 10-year follow-up visit at the age of 12-16 years, and performed IOS and spirometry, followed by a bronchodilation test. 64 of these teenagers had abnormal lung function at preschool age.

Results: Abnormal baseline values in preschool IOS were significantly associated with 1) low lung function, 2) the need for asthma medication and 3) the occurrence of asthma symptoms in adolescence. Preschool abnormal Rrs5 at baseline (z-score ≥ 1.645) showed positive predictive value for abnormal FEV1/FVC, asthma symptoms and asthma medication use at teenage by 62 % (p=0.001). Positive exercise challenge and bronchodilatation tests at preschool were only weakly predictive of asthma symptoms and the use of asthma medication at teenage.

Conclusions: Preschool IOS is associated with asthma at adolescence. The results suggest that early childhood IOS could aid in screening for persistent asthma.