Table 2

Characteristics of the study population and eligible children

Characteristics at birthStudy population
Total eligible population
p Value*
Gender (% boys)
Region (%)0.02
Study type (%)0.02
 Active intervention23.721.1
 Placebo intervention18.018.8
 Natural history58.360.1
Allergic mother (%)64.764.90.90
Allergic father (%)30.731.70.37
Mother's education (%)<0.001
Father's education (%)<0.001
Mother smoking pregnancy (%)9.916.20.009
Smoke exposure at home (%)18.922.10.001
Breast feeding duration (%)<0.001
 <3 months34.335.7
 ≥3 months51.444.1
Gas stove for cooking (%)83.782.90.33
Older siblings (%)48.348.90.57
Daycare attendance first year (%)24.923.80.27
Signs of dampness in the home (%)11.513.10.03
Cat(s) at home (%)29.829.50.79
Dog(s) at home (%)13.816.40.002
Type of home (%)<0.001
 Single-family dwelling73.469.7
 Apartment or flat26.630.3
Fitted carpet (%)
Estimated annual average concentrations of (median, interquartile range)
 PM2.5 (μg/m3)17.2 (14.7–18.1)17.3 (15.0–18.2)0.04
 Soot (10−5/m)1.77 (1.30–1.91)1.78 (1.35–1.92)0.01
 Nitrogen dioxide (μg/m3)25.8 (17.4–28.6)26.1 (18.7–29.3)0.001
  • * p Value for difference between study population and eligible children who did not participate.