Table 4.
Mean unadjusted and adjusteda changes in full-scale IQ score associated with an increase in blood lead concentration (log scale), from the 5th to 95th percentile of the concurrent blood lead level at the time of IQ testing.
| Blood lead variable | Unadjusted estimates [β(95% CI)] | Adjusted estimates [β(95% CI)] | Blood lead concentration (5th to 95th percentile, μg/dL) | IQ deficits [5th to 95th percentile (95% CI)] |
|---|---|---|---|---|
| Early childhood | −3.57 (−4.86 to −2.28) | −2.04 (−3.27 to −0.81) | 4.1–34.8 | 4.4 (1.7–7.0) |
| Peak | −4.85 (−5.16 to −3.54) | −2.85 (−4.10 to −1.60) | 4.0–34.5 | 6.1 (3.4–8.8) |
| Lifetime average | −5.36 (−6.69 to −4.03) | −3.04 (−4.33 to −1.75) | 6.1–47.0 | 6.2 (3.6–8.8) |
| Concurrent | −4.66 (−5.72 to −3.60) | −2.70 (−3.74 to −1.66) | 2.4–33.1 | 7.1 (4.4–9.8) |
Adjusted for site, HOME score, birth weight, maternal IQ, and maternal education. The addition of child’s sex, tobacco exposure during pregnancy, alcohol use during pregnancy, maternal age at delivery, marital status, and birth order did not alter the estimate, and these were not included in the model. The estimates for the covariates in the concurrent blood lead model were HOME score (β= 4.23, SE = 0.54), birth weight/100 g (β= 1.53, SE = 0.35), maternal IQ (β= 4.77, SE = 0.57), and maternal education (β= 1.12, SE = 0.46).