Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

AX6-9
Table AX6-2.2. Meta- and Pooled-Analyses of Neurocognitive Ability in Children
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
Lanphear et al. (2005) Pooled analysis of seven international prospective
studies involving 1,333 school-age children.
Primary outcome measure was full-scale IQ as
assessed by age-appropriate Wechsler scale.
Measures of exposure were concurrent, peak, avg
lifetime and “early” blood Pb (i.e. mean blood Pb
from 6-24 mos). Cord blood Pb was also
investigated for those studies that collected these
samples at birth. Multivariate regression models
were developed adjusting for site as well as 10
common covariates. Blood Pb measure with the
largest adjusted R 2 was nominated a priori as the
preferred index for relating Pb exposure to IQ in
subsequent analyses. Results evaluated by applying
a random-effects model.
Needleman and
Gatsonis (1990)
Meta analysis of 12 studies chosen on the basis of
quality—covariate assessment and application of
multiple regression techniques. Studies weighted on
basis of sample size. Studies divided according to
tissue analyzed (blood or teeth). Joint p-values and
avg effect sizes calculated using two different
methods.
Schwartz (1994) Meta analysis of 7 recent studies relating blood Pb to
IQ were reviewed, three longitudinal and four crosssectional.
Measure of effect was estimated decrease
in IQ for an increase in blood Pb from 10 to 20
µg/dL. Studies were weighted by the inverse of the
variances using random
Umbilical cord blood Pb
Serial postnatal blood Pb
Lifetime avg blood Pb 12.4
(range 4.1-34.8) µg/dL
Blood Pb
Tooth Pb
Concurrent blood Pb level exhibited the strongest
relationship with IQ, although results of regression analyses
for all blood Pb variables were similar. Steepest declines in
IQ were at blood Pb concentrations below 10 µg/dL. For
the entire pooled data set, a decline of 6.2 IQ points (95%
CI: 3.8, 8.6) was estimated for an increment in blood Pb
from 1 to 10 µg/dL.
Joint p-values for blood Pb studies were