Table 1.
Sample characteristics
| 5-year assessment |
11-year assessment |
|||
|---|---|---|---|---|
| N | Mean (Range) | N | Mean (Range) | |
| Child characteristics | ||||
| Gender (% female) | 104 | 59% | 201 | 55% |
| Age at testing (years) | 104 | 5.4 (4.8 – 6.2) | 201 | 11.3 (10.2 – 12.9) |
| Cord blood Pb levels (μg/dL) | 104 | 4.9 (0.8 – 27.1) | 198 | 4.8 (0.8 – 20.9) |
| Child blood Pb levels at testing (μg/dL) | 104 | 5.2 (1.0 – 37.1) | 198 | 2.66 (0.4 – 12.8) |
| Cord blood Hg (nmol/L) | 104 | 111 (9 – 520) | 198 | 105 (5 – 495) |
| Child blood Hg levels (nmol/L) | 104 | 48 (1 – 191) | 198 | 23 (1 – 170) |
| Cord PCB-153 (ng/g fat) | 104 | 124.1 (21.6 – 653.6) | 196 | 127.0 (9.7 – 653.6) |
| Child blood PCB-153 levels (ng/g fat) | 103 | 157.6 (7.5 – 1467.2) | 197 | 77.8 (4.1 – 809.5) |
| Haemoglobin level at testing (g/L) | 104 | 123 (88 – 172) | 198 | 130 (98 – 149) |
| Maternal characteristics | ||||
| Age (years) | 104 | 30.4 (21.4 – 45.1) | 200 | 39.1 (22.3 – 71.6) |
| Breastfeeding (% Yes) | 103 | 82% | 195 | 66% |
| Breastfeeding duration (months)a | 82 | 17.2 (0.1 – 60.0) | 128 | 18.2 (0.1 – 108.0) |
| Socioeconomic status (SES)b | 102 | 28.5 (8 – 57) | 201 | 28.8 (8 – 66) |
| Nonverbal intelligencec | 98 | 35.5 (13 – 54) | 195 | 35 (4 – 56) |
a
Mean duration of breastfeeding for mothers who breastfed;
b
Hollingshead index for the mother and her partner or, if she was not self-supporting, for her primary source of support (Hollingshead, 1975);
c
Raven Progressive Matrices (Raven et al., 1992).