Table 1

General characteristics of the eligible study population

Baseline characteristicsEligible study population (N=848)FENO (N=306)Rint (N=482)Specific IgE (N=380)
Gender (female)391/84846474741**
Allergic mother567/84867666672**
Allergic father289/84634353535
Maternal education level
Caesarean section86/8341010117**
Pets in the house (at birth)473/84456545554
Older sibling present422/84650495259**
Smoking during pregnancy147/83118181721*
Smoking in the house (at age 4)191/79824262324
Symptoms at baseline (age 3–4)
 Shortness of breath385/84845484647
 Cough at night§592/84870737069
Symptoms at age 8 years
 Inhaled steroid use109/722151512**16
 Doctor's diagnosis of asthma55/700886**9
  • For each variable, children with and without available data were compared. Significance of differences was tested using a χ2 test.

  • *p<0.05; **p<0.01.

  • Positive if mother reported smoking at least 4 weeks after estimated date of conception.

  • Smoking in the child's house more than once a week.

  • § In period without a cold, flu or chest infection.

  • Defined as a parental report of a doctor's diagnosis of asthma ever, in combination with parental report of symptoms in the past 12 months.

  • FENO, fraction of exhaled nitric oxide; IgE, immunoglobulin E; Rint, interrupter resistance.