Table 2.
Effect of lead and hemoglobin on IQ by DRD2 Taq IA genotype: results from stratified and interaction multivariate GEE models.a
| Lead [ln (μg/dL)] |
Hemoglobin (g/dL) |
|||||
|---|---|---|---|---|---|---|
| Model | Genotype | n | β-Coefficient (95% CI) | p-Value | β-Coefficient (95% CI) | p-Value |
| −4.22 (−7.10 to −1.36) | 0.004 | 2.30 (1.26 to 3.08) | < 0.0001 | |||
| 2: Stratified model | A1/A1 | 73 | −9.12 (−18.08 to −0.16) | 0.047 | −1.82 (−5.28 to 1.64) | 0.306 |
| A1/A2 | 290 | −4.35 (−8.24 to −0.44) | 0.023 | 2.24 (0.57 to 3.91) | 0.001 | |
| A2/A2 | 354 | −3.87 (−8.28 to 0.54) | 0.009 | 3.03 (1.60 to 4.45) | < 0.0001 | |
| 3: Stratified model | A1/A1 | 73 | −9.12 (−18.08 to −0.16) | 0.046 | −1.82 (−5.28 to 1.64) | 0.302 |
| A1/A2 + A2/A2 | 644 | −4.00 (−7.21 to −0.69) | 0.017 | 2.72 (1.58 to 3.86) | < 0.0001 | |
| 4: Interaction modelb | A1/A1 | 717 | −7.27 (−17.53 to −0.20) | > 0.28c | −1.32 (−4.66 to 2.02) | 0.022c |
| A1/A2 + A2/A2 | −3.94 (−7.10 to −0.79) | 2.72 (1.60 to 3.84) | ||||
a
Controlling for midarm circumference, age, sex, family income, parental education, and family size and accounting for school and classroom levels.
b
The model assessing the interaction of lead and DRD2 Taq IA controlled for confounding by hemoglobin and vice versa for the model assessing hemoglobin and DRD2 Taq IA interaction.
c
p-Values for interaction term coefficients.