Glen P. Aylward

Neurodevelopmental outcomes of infants born prematurely

ABSTRACT. Long-term follow-up of infants born prematurely is necessary to determine neurodevelopmental outcomes, particularly with the expansion of interest from major disabilities to high prevalence/low severity dysfunctions. Models of pathogenesis include changes due to developmental disruptions and to injury, the magnitude and type of change influenced by the infants age, and central nervous system recovery and reorganization. Alterations in neurogenesis, migration, myelination, cell death, and synaptogenesis occur even in the absence of insult. Despite increased knowledge regarding these processes, the functional significance of brain abnormalities is unclear. Because of methodologic problems in follow-up studies, it is difficult to characterize outcome definitively. Nonetheless, an acceptable degree of agreement across studies is found with regard to specific neurodevelopmental outcomes: motor/neurologic function, visuomotor integrative skills, IQ, academic achievement, language, executive function, and attention-deficit hyperactivity disorder/behavioral issues. In general, children born prematurely have more problems in these areas than do their normal birth weight counterparts. Suggestions for improved analyses and clarification of outcomes include use of cluster analysis, structural equation modeling, growth curve analysis, developmental epidemiologic approaches, and better control of background variables using risk indexes and factor scores. Better assessment techniques measuring functions documented to be at higher risk of problems are discussed.

Outcome studies of low birth weight infants published in the last decade: A metaanalysis

We conducted a metaanalysis and methods review of 80 studies, published in the last decade, that explored the outcome of low birth weight infants; 27% involved infants whose birth weights were less than or equal to 2500 gm (low birth weight), 44% less than or equal to 1500 gm (very low birth weight), and 29% less than or equal to 1000 gm (extremely low birth weight). Problems found in these studies were grouped into three categories: subject and methods issues, environmental factors, and outcome measurement. The combined average intelligence quotient/developmental quotient (IQ/DQ) of all low birth weight groups was 97.77 (SD 6.19); for control subjects the mean IQ/DQ was 103.78 (SD 8.16). This difference was statistically significant but perhaps not clinically significant. No differences in mean IQ/DQ scores were found among the low birth weight, very low birth weight, and extremely low birth weight subgroups. Statistically significant differences among all groups and control subjects were found when categoric data were analyzed, as were differences among the three subgroups; however, the variety of outcome criteria makes interpretation of the categoric analyses difficult.

Conceptual issues in developmental screening and assessment.

Effective screening requires an understanding of underlying conceptual issues and their relationship to pragmatic concerns. Pragmatic concerns include the concepts that there are many underlying reasons for an “abnormal” screening result; that sensitivity and specificity should be combined with relative risk when considering developmental outcome; and that patterns of congruence among motor, language, cognitive, and adaptive/personal social areas of development should be considered. Important conceptual issues include the following: there is continuity of underlying processes or functions in development; canalized behaviors might give the appearance of discontinuity; integrated functions are more predictive of later developmental levels than are individual functions; the “window” of assessment and the developmental emergence of a specific function will affect screening results; one must consider biologic and environmental risks and their specific effects; and different types of neural structures and their relationship to environmental input help to explain why screening results vary over time. J Dev Behav Pediatr 18:340-349, 1997.

Associations between Cognitive Function, Blood Lead Concentration, and Nutrition among Children in the Central Philippines

OBJECTIVE Because little is known about its effects on cognitive function among children in less-developed countries, we determined the impact of lead exposure from other nutritional determinants of cognitive ability. STUDY DESIGN Data were from a cross-sectional population-based stratified random sample of 877 children (age 6 months-5 years) participating in the Quality Improvement Demonstration Study we are conducting in the Philippines. With data from validated psychometric instruments, venous blood samples, and comprehensive survey instruments, we developed multi-stage models to account for endogenous determinants of blood lead levels (BLLs) and exogenous confounders of the association between BLLs and cognitive function. RESULTS A 1 microg/dL increase in BLL was associated with a 3.32 point decline in cognitive functioning in children aged 6 months to 3 years and a 2.47 point decline in children aged 3 to 5 years olds. BLL was inversely associated with hemoglobin and folate levels. Higher folate levels mitigated the negative association between BLL and cognitive function. CONCLUSIONS These population-based data suggest greater lead toxicity on cognitive function than previously reported. Our findings also suggest that folate and iron deficient children are more susceptible to the negative cognitive effects of lead. Folate supplementation may offer some protective effects against lead exposure.

Developmental Screening and Assessment : What Are We Thinking?

Glen P. Aylward, PhD, ABPP There is a burgeoning demand for developmental screening and assessment. This increase is attributable to the recent screening guidelines from the American Academy of Pediatrics,1 eligibility determination for early intervention, multidisciplinary clinic evaluations, a proliferation of neonatal intensive care unit follow-up programs, and research protocols requiring longitudinal measurement. Developmental screening and assessment is an issue we all face, regardless of the variety and diversity in what we do. Screening affords early identification of potential problems that can be verified by subsequent evaluation; developmental outcome, ascertained by assessment, is fast becoming a benchmark to determine the quality of perinatal practices or other medical interventions. Hence, there are pressures at both ends of the continuum: in the case of screening, quick tests to give quick scores; with assessment, more intricate tests to yield more detailed scores. In this commentary, I present a series of questions regarding theoretical and pragmatic issues. Within the ensuing discussion are musings, concerns, points to raise awareness, and cautions. No specific tests are targeted for criticism and it is readily acknowledged that some points may be controversial. The questions follow.

Predictive utility of the Bayley Infant Neurodevelopmental Screener (BINS) risk status classifications: clinical interpretation and application

Predictive validity and clinical implications of the increasingly popular Bayley Infant Neurodevelopmental Screener (BINS) risk status classifications have not been previously reported. In this longitudinal follow‐up study, the BINS was administered to high‐risk infants at 6, 12, and 24 months of age, and the McCarthy Scales at 3 years of age. Ninety‐two children were evaluated at 6 and 36 months, 105 at 12 and 36 months, and 118 at 24 and 36 months; 190, 125, and 140 infants were included in the comparisons at 6 to 12, 6 to 24, and 12 to 24 months. BINS risk status was classified as low, moderate, or high; or as a binary variable, LOWRISK/HIGHRISK. The three BINS items groups were moderately correlated. Consistency was most variable in the moderate‐risk group. BINS risk was predictive of 36‐month function in 18 out of 18 comparisons. Odds ratios, ranging from 2.76 to 54.70, were significant in 15 out of 18 logistic models. An early high‐risk classification was associated with increased probability of later developmental morbidity. The BINS offers an alternative to detailed assessment in high‐volume clinical applications and has good concurrent and predictive validity.

Relations Between Visual and Auditory Continuous Performance Tests in a Clinical Population: A Descriptive Study

Increased interest in auditory continuous performance tests (CPTs) exists despite the absence of a clear understanding about this procedure. The relation between auditory and visual CPTs and associations with IQ, achievement, and memory are evaluated in a referred sample of 634 children, ages 5.5 to 17.9. Age effects are found with CPT performance, regardless of modality. Total number correct or number of commissions correlations across tasks were greater than within-task number correct-number of commissions relations. The mean visual minus auditory correct difference score was 7.01; the mean commission difference score was -.85. Difference scores decreased with age and were not consistently related to other measures. Those with the lowest number correct on both CPTs (<25th percentile) were younger and had weaker short-term auditory memory and verbal learning skills; those falling in the problem quartile on commissions (>75th percentile) were younger and had poorer reading, verbal memory, and verbal learning. Total error scores (omissions + commissions) were inversely related to age. The auditory CPT has clinical utility, but other factors must be considered.

Individual and Combined Effects of Attention Deficits and Learning Disabilities on Computerized ADHD Assessment

The widespread use of computerized assessments in the diagnosis of attention deficit disorders (ADD/ADD-H) necessitates identification of factors that influence performance on these instruments. The individual and combined influence of two factors, attention deficits (determined by DSM-III) and learning disabilities (LD), on computerized ADHD assessment was evaluated in a clinic population of 253 children referred because of problems with attention or concentration, high activity levels, or poor academic achievement. Intelligence scores, levels of academic achievement, DSM-III diagnoses, parent and teacher rating scale data, and the presence of LDs were recorded. In ADD subjects, 66% also had one or more identified LD. In children without ADD, 64% were diagnosed as LD. Analyses of both summary scores (age-adjusted percentiles) and separate trial (raw) scores of a computerized assessment device indicated main effects for ADD/ADD-H on the continuous performance task (CPT) number correct and number of commissions. No main effect for LD was found. Delay task (DRL) results were not as clear; ADD effects were significant when raw scores, but not percentile scores, were used. It appears the computerized CPT task is influenced by ADD/ADD-H and is not affected independently by LD; however, age and IQmust be considered in such assessment. The delay task might not be as clinically useful.

The changing yardstick in measurement of cognitive abilities in infancy.

There are concerns regarding accurate measurement of cognitive function in infants, particularly those at biologic risk. Herein we discuss these issues and make recommendations. Concerns include: 1) secular changes in test norms, referred to as the Flynn effect; 2) changes in the content of revised test versions; 3) recent findings of higher mean scores in newer test versions when compared to previous scores; and 4) correction for prematurity. Caution is necessary when comparing the same test scores over extended periods of time, and using different versions of the same test when mean scores of the tests vary or evaluate different areas of functioning. Ideal solutions are not readily apparent and thus we provide several suggestions: control groups are essential for longitudinal studies; clinicians should not rely totally on cognitive scores; and further investigation of the Flynn effect in different subgroups of children at different ages is necessary.

Relationships Between Continuous Performance Task Scores and Other Cognitive Measures: Causality or Commonality?

Relationships among continuous performance test, IQ, achievement, and memory/learning scores were explored in a clinical sample of 1,280 children (M age = 9.4 years, M grade = 3.9). Intercorrelations among CPT measures were significant, but modest. Correlations between CPT measures and IQ, achievement, and memory/learning scores were also significant, but again generally weak. The CPT number correct scores were more strongly related to other cognitive measures than were commission (i.e., responding to incorrect stimuli) scores. The breadth and extent of associations among the CPT measures and the various cognitive/academic tasks suggest that all, to some extent, require attention and inhibition. The importance of routinely assessing attention and disinhibition in psychological testing is discussed.