TABLE 2

Characteristics of the study population

n (%)Mean±sdMedian (IQR)Range
Anthropometric data at birth
 Gestational age weeks39.6±1.239.8 (38.8–40.5)36.7–41.8
 Birth weight kg3.3±0.43.3 (3.0–3.6)2.1–4.9
 Length cm49.5±1.950.0 (48–51)44–57
Respiratory symptoms in the first year of life
 Weeks with symptoms5.3±4.64 (0–20)0–23
 Weeks with severe symptoms0.71±1.10 (0–1)0–6
Risk factors
 Male sex167 (51.8)
 Siblings159 (49.4)
 Caesarean section54 (16.7)
 Maternal asthma34 (10.5)
 Maternal atopy116 (36.1)
 Childcare62 (19.5)
 Maternal smoking in pregnancy27 (8.4)
 Parental smoking during infancy70 (21.7)
 Breastfeeding >26 weeks252 (78.3)
 Low maternal education202 (62.7)
Season of birth
 Spring87 (27.4)
 Summer83 (25.7)
 Autumn80 (24.8)
 Winter72 (22.6)
Outcomes at 6 year follow-up
 Any wheezing#105 (32.9)
 Current wheezing38 (11.7)
 Atopic disease+120 (37.5)
 SPT positive§37 (13.6)

Data are derived from 322 infants with a total of 16 864 observed symptom weeks. IQR: interquartile range; SPT: skin-prick test. #: defined as any wheezing episode between one and 6 years of age; : defined as wheezing over the past 12 months before follow-up; +: defined as allergic rhinitis, allergic asthma, or atopic dermatitis before follow-up; §: a SPT was completed in a subset of 270 children.