Table 1 Characteristics of the participants at age 28-30 years and comparison with non-participants

Age at testing (years)

29.0 ± 0.5

-

College graduate^a

81.4

-

Currently smoke^a

23.3

-

Alcohol use more than 2 drinks/week^a

34.9

-

Concussion or head trauma^a

23.8

-

Ever arrested^a

18.6

-

Male^a

48.8

51.4

0.77

White^a

93.0

91.2

0.70

First born^a

53.5

58.7

0.59

Weeks of gestation

40.0 ± 1.7

40.0 ± 2.1

0.96

Birth weight (kg)

3.4 ± 0.5

3.4 ± 0.5

0.76

Blood lead concentration (μg/dL)^b

Cord

6.5 ± 5.3

7.3 ± 5.3

0.43

6 months

8.0 ± 5.3

8.4 ± 7.5

0.74

12 months

10.0 ± 6.7

9.6 ± 6.5

0.72

24 months

7.7 ± 4.0

8.9 ± 6.9

0.28

4 years

6.7 ± 3.6

6.3 ± 4.3

0.64

10 years

3.0 ± 2.7

2.9 ± 2.3

0.79

IQ at age 4 years^b

117.7 ± 15.3

114.6 ± 14.3

0.22

IQ at age 10 years^b

117.7 ± 15.2

115.3 ± 13.9

0.36

Subjects' mothers

Age at delivery (year)^b

30.3 ± 4.3

30.1 ± 4.7

0.82

College graduate^a

60.0

59.3

0.49

Maternal IQ^b

122.8 ± 19.3

122.4 ± 17.8

0.90

HOME score^b

51.4 ± 4.4

51.0 ± 3.9

0.60

Tobacco use during pregnancy^a

27.5

26.9

0.94

Alcohol use during pregnancy^a

55.0

42.1

0.15