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. Author manuscript; available in PMC: 2019 Feb 1.
Published in final edited form as: Environ Res. 2018 Feb;161:588–598. doi: 10.1016/j.envres.2017.12.003

Table 1.

Sociodemographic characteristics of participants included in analysis (n=138)a and excluded from analysis due to missing tooth metals data (n=688)

Included in analysis Excluded from analysis
N Mean ± SD or % N Mean ± SD or %
Child sex:
 Male 64 46.4% 355 51.6%
 Female 74 53.6% 333 48.4%
Gestational age at birth (weeks) 135 38.9 ± 1.6 685 38.9 ± 1.5
 Preterm birth (<37 weeks gestation) 8 5.9% 42 6.1%
Birth weight (kg) 135 3.2 ± 0.4 687 3.1 ± 0.4
 Low birth weight (<2500 g) 4 3.0% 44 6.4%
First child:
 Yes 19 17.9% 3 0.5%
 No 87 82.1% 639 99.5%
Maternal age at delivery (yrs) 131 28.6 ± 5.8 686 28.9 ± 5.9
 <30 yrs old 86 65.6% 372 54.2%
Maternal education (yrs school) 130 11.2 ± 3.0 685 9.0 ± 3.9
 ≥12 yrs school 72 55.4% 218 31.8%
Maternal IQ score 120 93.6 ± 20.0 628 88.1 ± 22.2
Family SES:
 Low 65 55.1% 188 54.0%
 Medium 50 42.4% 151 43.4%
 High 3 2.5% 9 2.6%
Maternal smoking during pregnancy:
 Yes 2 1.7% 15 4.5%
 No 115 98.3% 320 95.5%
Hemoglobin at 1 yr of age 95 12.4 ± 1.4 380 12.0 ± 1.3
Hemoglobin at 2 yrs of age 111 13.2 ± 1.1 537 12.7 ± 1.2
Anemic at 1 or 2 years of ageb:
 Yes (hemoglobin ever <11.0 g/dl) 73 57.5% 429 73.0%
 No (hemoglobin never <11.0 g/dl) 54 42.5% 159 27.0%
Study cohort (years of child birth):
 1 (1994–1995) 2 1.4% 202 29.4%
 2A (1997–2002) 19 13.8% 243 35.3%
 2B (1998–2001) 33 23.9% 111 16.1%
 3 (2001–2006) 84 60.9% 132 19.2%
Age at WRAVMA testing (yrs) 138 8.0 ± 1.4 688 10.6 ± 2.6
WRAVMA score: Total 138 98.0 ± 10.6 688 98.1 ± 13.1
WRAVMA score: Visual motor 138 98.0 ± 11.3 688 96.8 ± 12.9
WRAVMA score: Visual spatial 138 94.9 ± 13.4 688 94.2 ± 14.7
WRAVMA score: Fine motor 138 104.0 ± 13.7 688 103.0 ± 13.0
a

Missing data for some covariates: birth weight (n=3), gestational age (n=3), first child (n=32), mother’s age at delivery (n=7), mother’s education (n=8), mother’s IQ (n=18), SES (n=20), mother smoked during pregnancy (n=21), hemoglobin at 1 yr (n=43), hemoglobin at 2 yrs (n=27), anemic (n=11).

b

Anemic defined by WHO for children 6–59 months of age as hemoglobin <11.0 g/dl, after altitude adjustment. Hemoglobin levels in participants were adjusted for altitude by −0.8 g/dl (participants reside at ~2000 m elevation in Mexico City) to define anemia status.