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

From: Low-level environmental lead exposure in childhood and adult intellectual function: a follow-up study

Characteristic Subjects who participated in IQ testing (n = 43) Subjects who did not participate (n = 105) p-value
Subjects    
Age at testing (years) 29.0 ± 0.5 -  
College graduatea 81.4 -  
Currently smokea 23.3 -  
Alcohol use more than 2 drinks/weeka 34.9 -  
Concussion or head traumaa 23.8 -  
Ever arresteda 18.6 -  
Malea 48.8 51.4 0.77
Whitea 93.0 91.2 0.70
First borna 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 yearsb 117.7 ± 15.3 114.6 ± 14.3 0.22
IQ at age 10 yearsb 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 graduatea 60.0 59.3 0.49
Maternal IQb 122.8 ± 19.3 122.4 ± 17.8 0.90
HOME scoreb 51.4 ± 4.4 51.0 ± 3.9 0.60
Tobacco use during pregnancya 27.5 26.9 0.94
Alcohol use during pregnancya 55.0 42.1 0.15
  1. a(% Yes) bMean ± SD