Table 1

Characteristics of study population by exposure to NO2 in the cohort INMA–Granada, 2000–6

Exposure to NO2 (μg/m3)
(Sample size at age 4 years, n)(68)(70)(72)(210)
Covariates from birth to 4th year
Place of residence at age 4 years (%)
 Rural (R)
Birth weight (kg) (mean)*
Birth length (cm) (mean)50.650.850.850.7
Gestational age (weeks) (mean)39.339.039.439.2
School term at evaluation (%)
 3rd year, 3rd term (R)32.434.333.333.3
 4th year, 1st term26.528.626.427.1
 4th year, 2nd term30.927.129.229.0
 4th year, 3rd term10.310.011.110.5
Age at evaluation (months) (mean)51.251.551.251.3
Educational level (%)
 University (R)8.811.422.214.3
 Secondary school73.567.165.368.6**
 Only primary school17.621.412.517.1**
Occupation status (%)
 Unemployed (R)64.750.037.550.5
Parity at child's birth (%)
 0 (R)
 2 or more17.612.911.113.8
Breastfeeding (%)
 ≥28 weeks (R)
 16–27.9 weeks33.828.637.533.3
 2–15.9 weeks33.844.334.737.6
 <2 weeks29.510.012.513.8
Type of delivery (%)
 Vaginal (R)77.972.973.674.8
 With forceps or other10.310.09.710.0
Marital status at child age of 4 years (%)
 With a stable partner (R)98.5100.095.898.1
 Without a stable partner1.*
Smoking during pregnancy (%)
 No (R)80.971.479.277.1
Mental health (mean score)†10.811.911.311.4
Mother-to-infant attachment (mean score)‡74.474.673.974.3
Age at child's birth (years)31.731.632.732.0
Educational level (%)
 University (R)10.314.323.616.2
 Secondary school50.065.761.159.0**
 Only primary school39.720.011.122.9***
Mental health (mean score)†9.610.411.210.2*
Father-to-infant attachment (mean score)‡74.475.273.174.5
  • * p Value ≤0.10;

  • ** p value ≤0.05;

  • *** p value ≤0.001.

  • Mean score for the general mental health scale; a higher score indicates greater psychological distress.

  • Mean score for the parent-to-infant attachment scale; a higher score indicates a closer bond of affection.

  • (R) Reference category.

  • Smoking during pregnancy: at least one cigarette/day in the third trimester.

  • NO2, nitrogen dioxide.