Characteristics of study population by exposure to NO2 in the cohort INMA–Granada, 2000–6
| Exposure to NO2 (μg/m3) | ||||
| <15.40 | 15.40–24.75 | >24.75 | All | |
| (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) | 45.6 | 0.0 | 1.4 | 15.2 |
| Suburban | 50.0 | 12.9 | 0.0 | 20.5*** |
| Metropolitan | 4.4 | 74.3 | 63.9 | 48.1*** |
| Urban | 0.0 | 12.9 | 34.7 | 16.2*** |
| CHILD | ||||
| Birth weight (kg) (mean) | 3.3 | 3.2 | 3.4 | 3.3* |
| Birth length (cm) (mean) | 50.6 | 50.8 | 50.8 | 50.7 |
| Gestational age (weeks) (mean) | 39.3 | 39.0 | 39.4 | 39.2 |
| School term at evaluation (%) | ||||
| 3rd year, 3rd term (R) | 32.4 | 34.3 | 33.3 | 33.3 |
| 4th year, 1st term | 26.5 | 28.6 | 26.4 | 27.1 |
| 4th year, 2nd term | 30.9 | 27.1 | 29.2 | 29.0 |
| 4th year, 3rd term | 10.3 | 10.0 | 11.1 | 10.5 |
| Age at evaluation (months) (mean) | 51.2 | 51.5 | 51.2 | 51.3 |
| MOTHER | ||||
| Educational level (%) | ||||
| University (R) | 8.8 | 11.4 | 22.2 | 14.3 |
| Secondary school | 73.5 | 67.1 | 65.3 | 68.6** |
| Only primary school | 17.6 | 21.4 | 12.5 | 17.1** |
| Occupation status (%) | ||||
| Unemployed (R) | 64.7 | 50.0 | 37.5 | 50.5 |
| Employed | 35.3 | 50.0 | 62.5 | 49.5** |
| Parity at child's birth (%) | ||||
| 0 (R) | 47.1 | 50.0 | 45.8 | 47.6 |
| 1 | 35.3 | 37.1 | 43.1 | 38.6 |
| 2 or more | 17.6 | 12.9 | 11.1 | 13.8 |
| Breastfeeding (%) | ||||
| ≥28 weeks (R) | 2.9 | 2.9 | 6.9 | 4.3 |
| 16–27.9 weeks | 33.8 | 28.6 | 37.5 | 33.3 |
| 2–15.9 weeks | 33.8 | 44.3 | 34.7 | 37.6 |
| <2 weeks | 29.5 | 10.0 | 12.5 | 13.8 |
| Type of delivery (%) | ||||
| Vaginal (R) | 77.9 | 72.9 | 73.6 | 74.8 |
| Caesarean | 11.8 | 17.1 | 16.7 | 15.2 |
| With forceps or other | 10.3 | 10.0 | 9.7 | 10.0 |
| Marital status at child age of 4 years (%) | ||||
| With a stable partner (R) | 98.5 | 100.0 | 95.8 | 98.1 |
| Without a stable partner | 1.5 | 0.0 | 4.2 | 1.9* |
| Smoking during pregnancy (%) | ||||
| No (R) | 80.9 | 71.4 | 79.2 | 77.1 |
| Yes | 19.1 | 28.6 | 20.8 | 22.9 |
| Mental health (mean score)† | 10.8 | 11.9 | 11.3 | 11.4 |
| Mother-to-infant attachment (mean score)‡ | 74.4 | 74.6 | 73.9 | 74.3 |
| Age at child's birth (years) | 31.7 | 31.6 | 32.7 | 32.0 |
| FATHER | ||||
| Educational level (%) | ||||
| University (R) | 10.3 | 14.3 | 23.6 | 16.2 |
| Secondary school | 50.0 | 65.7 | 61.1 | 59.0** |
| Only primary school | 39.7 | 20.0 | 11.1 | 22.9*** |
| Mental health (mean score)† | 9.6 | 10.4 | 11.2 | 10.2* |
| Father-to-infant attachment (mean score)‡ | 74.4 | 75.2 | 73.1 | 74.5 |
↵* 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.