Table 1– Characteristics of the study population
VariableData available for all childrenChildren with asthmaChildren without asthma
Subjects499268231
Recruitment category
Probands164 (61.2)0 (0)
Relatives96 (35.8)173 (74.9)
Population-based controls8 (3.0)58 (25.1)
Male sex499173 (64.6)106 (45.9)
Age at recruitment yrs49910.8 (9.0–12.9)11.4 (8.7–13.5)
Respiratory infection in early life499138 (51.5)66 (28.6)
Exposure to ETS in early life489122 (46.6)114 (50.2)
Atopy#486226 (86.6)91 (40.4)
In sensitised children, ≥2 positive SPT166 (73.5)47 (51.6)
IgE IU·mL−1489383 (151–815)58 (21–177)
Peripheral blood eosinophils %4846.5 (4.0–10.8)3.1 (2.0–5.0)
Peripheral blood eosinophils cells·mm−3484434 (270–700)210 (120–360)
FEV1 % pred47392.9 (84.3–101.3)94.9 (88.3–102.3)
Bronchial hyperresponsiveness+310127 (92.0)75 (43.6)
Used inhaled corticosteroids in the last 12 months494102 (38.5)2 (0.9)
Ever hospitalised for asthma26772 (27.0)
Age at onset of asthma yr2684 (2–6)
Early-onset asthma (4 yrs old)167 (62.3)
Late-onset asthma (>4 yrs old)101 (37.8)
Asthma persisting in young adulthood (persistent asthma)236128 (54.2)
Early onset in subjects with persistent asthma84 (65.6)
Late onset in subjects with persistent asthma44 (34.4)
Asthma inactive in young adulthood (remittent asthma)236108 (45.8)
Early onset in subjects with remittent asthma62 (57.4)
Late onset in subjects with remittent asthma46 (42.6)
  • Data are presented as n, n (%) or median (interquartile range). ETS: environmental tobacco smoke; SPT: skin prick test; Ig: immunoglobulin; FEV1: forced expiratory volume in 1 s; % pred: % predicted. #: atopy was defined as a positive SPT to at least one of 11 common allergens; : total serum IgE was measured by immunoassay; +: bronchial hyperresponsiveness was defined as ≥20% decline of FEV1 for a methacholine cumulative dose ≤4 mg.