Comparing the effects of perinatal and later childhood lead exposure on neuropsychological outcome.
ABSTRACT Blood lead values (PbB) from cord blood and maternal samples as well as present PbB from venous blood samples were available for 114 six- to seven-year-old children living in or near the city of Nordenham (FRG). These children represented 30% of all children born between July 1975 and August 1976 in the district hospital (N = 383). The range of cord blood PbB was 4-31 micrograms/100 ml (mean = 8.2 micrograms/100 ml) and of maternal PbB was 4-30 micrograms/100 ml (mean = 9.3 micrograms/100 ml), whereas the range for present PbB was 3.9-22.8 micrograms/100 ml (mean = 8.2 micrograms/100 ml). The degree of correlation between maternal and cord blood PbB was 0.79, despite the poor technical quality of many cord blood samples as compared to maternal blood samples (less coagulation). These children were given a battery of neurophysiological and neuropsychological tests. The present report is restricted to psychological performance measures. The test battery covered intelligence (reduced Wechsler Intelligence Scale for Children), visual-motor performance (Bender Test, GFT), serial reaction performance (Wiener Reaction Device), and cued as well as choice reaction times. After correction for confounding by means of stepwise multiple-regression analysis, few significant associations between blood lead levels and performance deficit occurred. In general the degree of association was somewhat stronger for present PbB than for perinatal PbB: With increasing present PbB there was a borderline drop of performance IQ (P less than 0.1), as well as a significant disruption of serial reactions, which was more pronounced for the difficult (P less than 0.01) than for the easier version of the Wiener Device (P less than 0.05). A similar but less pronounced pattern of associations was observed for maternal PbB but not for cord blood PbB. Some influence of perinatal lead exposure on later performance can, thus, still be detected if, in addition to cord blood PbB, maternal PbB is taken into account as well.
- SourceAvailable from: washington.edu[show abstract] [hide abstract]
ABSTRACT: Three meta-analyses on the relationship of low levels of lead to loss of IQ points in children, which included a total of 26 well-controlled studies, provided the raw materials for the analysis presented here. Despite some key limitations, results of lead-IQ studies have been instrumental in setting public policy. In this paper, five shortcomings in these studies are addressed, which, when taken together, suggest greater caution in the interpretation of the lead-IQ data. In addition, some other issues are addressed concerning the IQ loss attributed to low levels of lead.Archives of Clinical Neuropsychology 06/2001; 16(4):303-41. · 2.00 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: This study is among the first to examine specific neurobehavioral deficits in children exposed at very low lead levels. A systematic analysis for the presence of a threshold of lead exposure was conducted. The sample consisted of 246 African American, inner-city children from whom blood lead concentrations were assessed at 7.5 years of age. The results consistently show neurobehavioral deficits in relation to low levels of lead in the areas of intelligence, reaction time, visual-motor integration, fine motor skills, attention, including executive function, off-task behaviors, and teacher-reported withdrawn behaviors. Effects were identified in the specific domains of attention, executive function, visual-motor integration, social behavior, and motor skills, which have been previously suggested as part of lead's "behavioral signature". Visual inspection of nonparametric regression plots suggested a gradual linear dose-response relation for most endpoints. No threshold discontinuity was evident. Regression analyses in which lead exposure was dichotomized at 10 microg/dl were no more likely to be significant than analyses dichotomizing exposure at 5 microg/dl. Given that associations were found between lead levels as low as 3 microg/dl for multiple outcomes, these data provide additional evidence that there is no apparent lower bound threshold for postnatal lead exposure.Neurotoxicology and Teratology 01/2004; 26(3):359-71. · 3.18 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: This paper addresses the points raised by five groups of scientists who were invited to respond to my article on the relationship of low blood lead to IQ loss. I dealt with these comments as a scientist who believes that the case is not closed on this topic, as some respondents believe, but that debate is healthy and can move the field to the next level. The criticisms about the measurement of parents' IQ, multiple comparisons, the linearity of the lead-IQ relationship, and the societal consequences of a few points of IQ loss appear weak in the face of an array of evidence that bears on these topics. However, criticisms about my emphasis on the need to control for a wide variety of potential confounders has validity. Ultimately, however, the case for the relationship of low blood lead to IQ loss seems to rest tenuously on data obtained from samples that included numerous subjects with moderate to severe levels of blood lead.Archives of Clinical Neuropsychology 06/2001; 16(4):403-31. · 2.00 Impact Factor