Clinical implications of airway obstruction with normal or low FEV 1 in childhood and adolescence

Background Airway obstruction is defined by spirometry as a low forced expiratory volume in 1 s (FEV 1) to forced vital capacity (FVC) ratio. This impaired ratio may originate from a low FEV 1 (classic) or a normal FEV 1 in combination with a large FVC (dysanaptic). The clinical implications of dysanaptic obstruction during childhood and adolescence in the general population remain unclear. Aims To investigate the association between airway obstruction with a low or normal FEV 1 in childhood and adolescence, and asthma, wheezing and bronchial hyperresponsiveness (BHR). Methods In the BAMSE (Barn/Child, Allergy, Milieu, Stockholm, Epidemiology; Sweden) and PIAMA (Prevention and Incidence of Asthma and Mite Allergy; the Netherlands) birth cohorts, obstruction (FEV 1:FVC ratio less than the lower limit of normal, LLN) at ages 8, 12 (PIAMA only) or 16 years was classified as classic (FEV 1