Table 3—

Prevalence of selected potential confounders in the cohort.

VariableSubjectsPrevalence %
Collected during pregnancy
 Mother smoking during pregnancy583 (4079)14
 Allergic mother1281 (4114)31
 Intervention study855 (4146)21
 Natural history study3291 (4146)79
 Allergen-free mattress cover416 (4146)10
  North region of country1275 (4146)31
  Middle region of country1647 (4146)40
  West region of country1224 (4146)29
Collected at 3 months old
 Male2035 (3934)52
 Female1899 (3934)48
 Smoking in home1121 (3903)29
 Allergic father1172 (4051)29
 Gas stove3236 (3911)83
 Unvented gas water heater192 (3760)5
 Any pets in home2011 (3905)51
 Any other siblings1986 (3919)51
 Any breastfeeding at 3 months1827 (3883)47
Collected at age 1 yr
 Any mold in home1215 (3704)33
  ≥High school education1966 (3709)53
  ≤Medium level professional education1743 (3709)47
  ≥High school education1730 (3546)49
  ≤Medium level professional education1816 (3546)51
Collected at age 2 yrs
 Netherlands ethnicity3478 (3690)94
 Other ethnicity212 (3690)6
Collected at age 4 yrs
 Smoking in home847 (3532)24
 Gas stove2545 (3218)79
 Unvented gas water heater102 (3312)3
 Any other siblings2972 (3495)85
 Any mold in home#1297 (3523)37
 Any pets in home1864 (3456)54
  • Data for subjects are presented as number with the characteristic (total number of subjects evaluated). #: Includes presence of mould, water damage and visible moisture in any of four specified rooms; : refers to cats, dogs, rodents or birds. Prevalence of pets, gas water heater and gas stove at 4 yrs may not be completely accurate due to incomplete data (questions are asked only for cases in which there was a change since the previous year's questionnaire), which leads to a slight increase in missing values.