Reduced baseline lung function in asymptomatic and symptomatic infants with recurrent asthma-like symptoms

Recurrent asthma-like symptoms (RALS) in infants, defined as three or more physician-diagnosed episodes of wheezing and cough in the past 12 months, are the most common clinical presentation of asthma during the first two years of life. During exacerbations, patients may experience severe episodes and often require emergency department visits or hospitalisation. However, there is limited information on lung function (LF) during symptomatic periods compared to asymptomatic periods and in healthy controls.

The baseline LF of 264 infants aged < 15 months with RALS (94 symptomatic and 170 asymptomatic) was measured using rapid thoracic compression from the raised volume technique, and 44 healthy infants were included as the control group. The measurements were converted to z-scores for analysis and comparison.

The mean LF was significantly lower in symptomatic than in asymptomatic infants. Additionally, LF in the asymptomatic group was significantly lower than that in healthy infants. Tobacco smoking during pregnancy, frequent wheezing episodes (≥7), and family history of asthma were significantly associated with a higher proportion of abnormal FEV0.5 (z-score < -1.64) across the entire group of RALS infants.

Infants with RALS exhibit markedly reduced LF during symptomatic episodes. Furthermore, even when asymptomatic, they exhibit substantially lower LF than normal infants. These functional features support the notion that LF deficits are present very early in life in infants with RALS. This may also help explain the high prevalence of frequent and severe episodes observed in infants with RALS in clinical practice. © 2026 Codon Publications. Published by Codon Publications.