Bayley Mental Development

Schroeder et al. (1985) and Schroeder and Hawk (1987) evaluated 104 black children of lower socioeconomic status at ages 10 months to 6.5 years, using the Bayley Mental Development Index (MDI) or Stanford-Binet IQ Scale. Hierarchical backward stepwise regression analyses indicated that PbB levels (range 6-59 pg/dL) were a significant source of the variance in IQ and MDI scores after controlling for socioeconomic status and other factors. Fifty of the children were examined again 5 years later, at which time PbB levels were 30 pg/dL. The 5-year follow-up IQ scores were inversely correlated with... 

Consistent evidence indicating low predictive validity of Bayley scale performance when administered below 2 y (Bendersky and Lewis, 2001 Colombo, 1993) inconsistency of findings when comparing Bayley mental development scores of infants... 

To assess the association between prenatal/early postnatal lead exposure and development, we followed a group of urban US infants from birth to 2 years of age. Estimates of the association between lead and Bayley Mental Development Index (MDI) scores at ages 6, 12, 18, and 24 months were obtained using several regression options. In all multivariate models examined, MDI scores were associated with umbilical cord blood lead levels, but not with postnatal blood lead levels. Infants with high cord blood lead levels (10-25 jUg/dl) consistently scored 4 to 8 points lower than infants with low cord blood lead levels (< 3 jUg/dl). Infants vulnerability to lead s developmental toxicity appears to be greatest during the fetal period. 

A subset of possible predictor variables was then identified and this included home environment assessment score at year 1 (HOMEl) and year 2 (HOME2), obstetric complication score, birth weight, birth order, socioeconomic class of the father in year 1 (SCI) and in year 2 (SC2). The dependent variables considered were Bayley mean score at year 1 and year 2, Bayley Mental Development Index (MDI) at year 1 and year 2 and the Bayley Psychomotor Development Index (PDI) at year 1 and year 2. The overall mean scores at year 1 and year 2 were significantly correlated (r = 0.39). The mean values for these dependent variables are set out in Table 3. 

Vimpani GV, Baghurst PA, Wigg NR, et al. 1989. The Port Pirie cohort study—cumulative lead exposure and neurodevelopmental status at age 2 years Do HOME scores and maternal IQ reduce apparent effects of lead on Bayley Mental scores In Smith M. Grant LD, Sors A, eds. Lead exposure and child development An international assessment. Lancaster, UK Kluwer Academic Press. 

What are these subclinical effects Very simply, they are effects that occur at blood lead levels below those that produce clinically measurable effects - they occur in the absence of any sign of overt lead poisoning. These effects can be detected only by studying various forms of behavior, such as degree of hyperactivity and classroom attention span, and performance on various tests of intelligence and mental development. Deficits in neurobehavioral development, as measured by two widely used tests - the Bayley and McCarthy Scales - have been reported in children exposed prenatally (via maternal blood) to blood... 

The follow-up evaluations at both 6 and 12 months included the administration of the Bayley Scales of Infant Development (Gladen et al. 1988). This exam yields a mental development index (MDl) score and a psychomotor development index (PDI) score, both of which are scaled like a standard IQ test. There were 858 infants (92%) from the original cohort who participated in the study past the neonatal period. 

Other findings (18) suggest that the first postnatal day (PND) is a unique time for a highly sensitive assessment of later development. Based on continuous recordings over the first 2 PND, it was observed that on PND 1, six sleep measures were related to 6-mo Bayley mental and motor scores. By PND 2, two measures showed such relationships. 

As mentioned above, age norms for the Spanish population have been developed for Cattell s test as well as for Bayley s (0-2%-year-olds) and McCarthy s (2%-6-year-olds) tests. Test performance on the two latter test series is represented by a Mental Development Score and a Psychomotor Development Score. 

GDS, Gesell Development Schedules CBCL, Child Behavior Checklist WPPSI-R, Wechsler Preschool and Primary Scale of Intelligence-Revised BSID-IL Bayley-II Scales of Child Development ETS, Environmental Tobacco Smoke MDL Mental Development Index PDI, Physical Development Index RCPM, Raven Coloured Progressive Matrices.Included are studies related to the events of September, 11,2001, as well as international studies of PAH exposures. 

In this paper we examine two aspects of the association between lead exposure and infants scores on the Mental Development Index (MDI) of the Bayley Scales of Infant Development at 6, 12, 18 and 24 months of age (1) the stability of the estimate when different approaches to data analysis are taken and (2) inter- and intra-individual stability of the estimate of the association over time. 

Results from several cohort studies are now available. Bellinger et al (1986) failed to find any relation, for middle-class infants, of 6-month and 12-month blood lead levels (PbB) and the Mental Development Index (MDI) of the Bayley Scales of Infant Development. Dietrich et al. (in press) reported a significant relationship of 3-month, but not 6-month, PbB with 6-month MDI... 

To assess the mental and psychomotor development of infants exposed to PCBs both pre- and postnatally, the Dutch standardized version of the Bayley Scales of Infant Development were administered at 3, 7, and 18 months of age. Both the MDI and the PDI were included in the assessments. The tests were performed at the infant s home in the presence of the parent(s) (Koopman-Esseboom et al. 1996). The evaluations of the infants using the Bayley Scales of Infant Development were undertaken only for the 207 children from Rotterdam. Rotterdam is an urban area thought to have higher exposures to PCBs than Groningen, a semi-urban area in northern Holland. 

Nearly all tests used for assessing the children s mental level had, at an earlier stage, been adapted to the Spanish population that was the case with, for example, the Bayley Scales of Infant Development, the McCarthy Scales of Children s Abilities, and Cattell s Culture Fair Intelligence Test. Some of the psychomotor tests that were not adapted to Spain were included in the survey anyway because of their expected relevance. 

Bayley, N. (1970) The development of mental abilities. In Mussen, P.H. (ed.) Carmichael s Manual of Child Psychology, Vol. 1 (New York John Wiley)... 

Measures chosen were comparable with those used in the other longitudinal studies being conducted The Bayley Scales of Infant Development (1969) were used to measure mental and psychomotor development at 6 months, 12 months and 24 months the Bayley Infant Behaviour Record and the Toddler Temperament Questionnaire (Fullard et al, 1978) to monitor behavioural problems. At 3 years the McCarthy Scales of Children s Abilities (1972) replaced the Bayley Scales, and this test was employed also at 4 years and, currently, at 5 years. At 5 years a special computer vigilance task is being employed to assess attention span and attain reaction time measures. (This task was written by Jacobson and Jacobson at Wayne State University, Detroit, USA.)... 

At age 24 months, the developmental status of each child was formally measured using the mental (MDI) and psychomotor (PDI) subscales of the Bayley Scales of Infant Development (Bayley, 1969). These scales were administered to all children by one clinical psychologist who has remained blind to blood lead results throughout the study. Testing was undertaken on a different day from that on which other interviewing and blood collection took place. 

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