Table 1.
Comparison of participants with and without lead data at age 11 years on primary study variables.
| Alive at age 38 years | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Full Sample | Lead Data at age 11 | No Lead Data at age 11 | Lead vs No Lead | |||||||
| (N = 1037) | (N = 565) | (N = 442) | ||||||||
| N | Mean | % or SD | N | Mean | % or SD | N | Mean | % or SD | P Value | |
| Male | 535 | (51.7%) | 303 | (53.6%) | 214 | (44.8%) | 0.10 | |||
| Childhood Blood-Lead Level | 565 | 10.99 | (4.63) | – | – | |||||
| Maternal Verbal IQ | 1011 | 39.75 | (14.77) | 557 | 40.41 | (14.22) | 425 | 39.19 | (15.42) | 0.20 |
| WISC-R Childhood Full-Scale IQ | 986 | 100.00 | (15.00) | 563 | 101.01 | (14.22) | 398 | 98.91 | (15.53) | 0.03 |
| Childhood Socioeconomic Status | 1031 | 3.75 | (1.14) | 563 | 3.80 | (1.12) | 438 | 3.69 | (1.17) | 0.13 |
| WAIS-IV Age-38 Full-Scale IQ | 942 | 100.00 | (15.00) | 542 | 101.16 | (14.82) | 400 | 98.43 | (15.11) | 0.006 |
| Age-38 Socioeconomic Status | 953 | 48.83 | (17.11) | 550 | 49.75 | (17.12) | 403 | 47.58 | (17.03) | 0.05 |
Note. Maternal verbal IQ was assessed with the Thurstone scale, which is not scaled to a mean of 100.
Note. Socioeconomic status was assessed in childhood using the Elley-Irving scale (range 1 lowest – 6 highest) and at age 38 years using the New Zealand Socioeconomic Index-2006, (NZSEI-06; range 10 lowest – 90 highest).
Note. SD = standard deviation