The National Children's Study Research Plan A Review (2008) / Chapter Skim
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3 Priority Outcome and Exposure Measures
3 Priority Outcome and Exposure Measures
Pages 53-100
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From page 53... ...
The study's geographical dispersion and the varied socioeconomic and demographic characteristics of the study population have important implications for the collection of exposure measures. This chapter first discusses each priority outcome area, which necessarily includes some discussion of the kinds of exposures that are proposed 53
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From page 54... ...
Priority Outcomes For each priority outcome area, the discussion summarily describes the proposed hypotheses regarding specific outcomes and associated environmental factors as presented in the NCS research plan. It then offers the panel's assessment in terms of public health significance and soundness of concepts and methodology.
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From page 55... ...
Second, the NCS could reconsider its decision not to obtain dental records to establish maternal periodontal disease (NCS Research Plan, Vol.
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From page 56... ...
Nevertheless, following up children into the later years of childhood will help track whether the impact of the reproductive outcomes persists beyond early childhood and what risk factors determine persistence and severity. Prepregnancy exposure measures Many of the important questions about the effects of various exposures on pregnancy outcomes may require obtaining assays before pregnancy.
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From page 57... ...
The question of statistical power also affects the hypotheses regarding altered maternal glucose metabolism and birth defects. The research plan argues the importance of this question from the rise in obesity and type 2 diabetes.
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From page 58... ...
. The research plan proposes ultrasound examinations in the second and third trimesters; however, the second trimester ultrasound will be obtained only if the mother has not already had an early ultrasound for gestational age dating (NCS Research Plan, Vol.
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From page 59... ...
Recommendations We have identified a number of issues and concerns with the NCS research plan proposals for assessing environmental influences on pregnancy outcomes. We offer two recommendations for steps that we judge to be of high priority for the NCS: one on the set of hypotheses that merit study and the other on the need for more specificity of the proposed research on pregnancy outcomes, which will be among the very first for which data are to be collected.
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From page 60... ...
, anxiety disorders, depression, and schizophrenia and relating them to specific environmental exposures. The NCS will examine four broad hypothesized relationships (meta-hypotheses, NCS Research Plan, Vol.
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From page 61... ...
However, as stated earlier, the National Institute of Child Health and Human Development (NICHD) study staff have indicated that resources are not available at this time to abstract medical records except at birth (see Chapter 2)
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From page 62... ...
The research plan spells out five broad meta-hypotheses (NCS Research Plan, Vol.
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From page 63... ...
Assessment: Public Health Significance and Conceptual Concerns Both the domain of neurodevelopment and behavior disorders and that of normal child health and development are clearly important areas to which the NCS could make significant contributions. However, the research plan has serious conceptual limitations in each domain that warrant concern.
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From page 64... ...
The hypotheses that propose to link environmental exposures to adverse neurodevelopment and behavioral outcomes reflect a biomedical approach that appears limited in its ability to contribute to understanding of this complex area. For example, the hypothesis to link repeated, low-level exposure to nonpersistent pesticides to poor neurobehavioral and cognitive skills is important because of widespread levels of exposure and the likelihood that children are more sensitive to exposures than adults.
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From page 65... ...
, the NCS proposes to look separately at the effects of parenting behavior, child care experiences, access to and use of health and social services, and such child characteristics as intelligence and temperament, on healthy child development. Pathways for the separate and interactive effects of these factors are not clearly specified, nor are the factors always clearly defined.
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From page 66... ...
at 12 months; • intelligence tests -- perhaps Woodcock-J scales at later ages or Bay ley or Kaufman scales; • unspecified assessments of executive function and attention; • Rothbart IBQ-R measures of temperament; • videotaped mother-child interaction at 6 months; and • BITSEA. This list appears ad hoc and not well informed by contemporary child development research or well focused on specific hypotheses or domains of interest.
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From page 67... ...
Recommendation Our discussion has identified a large number of concerns. Most important is the need for the NCS to justify the selected outcomes of interest and related exposure measures, given the wide range of possible outcomes the NCS could study in the two domains of neurodevelopment and behavior and normal health and functioning.
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From page 68... ...
Description The NCS proposes to examine six hypotheses about risk factors for childhood asthma (NCS Research Plan, Vol.
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From page 69... ...
Therefore, the major strength of the NCS is the ability to study asthma incidence beginning with prenatal exposures. Follow-up into the later years of childhood is necessary to understand whether asthma symptoms persist beyond early childhood and what risk factors determine persistence and severity.
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From page 70... ...
In addition, the study proposes to relate the development of type 1 diabetes to an interaction between genetic susceptibility, early exposure to viral infections, and early exposure to cow's milk protein or other dietary components. The NCS research plan does include getting growth measures as direct observations. In addition, the NCS will be obtaining related blood samples for lipids and glucose metabolism abnormalities.
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From page 71... ...
Assessment: Conceptual and Methodological Concerns The large sample size of the NCS provides an important opportunity to evaluate such hypotheses as the effects of impaired maternal glucose metabolism and intrauterine growth restrictions on childhood obesity. In general, however, the hypotheses selected by the NCS appear too narrowly focused to result in new information that could ultimately reduce the epidemic in childhood obesity and curtail its adult sequelae.
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From page 72... ...
Description The NCS singles out repeated mild traumatic brain injury (rMTBI) for attention in the broad field of unintentional childhood injury, positing that it has a cumulative adverse effect on neurocognitive development (NCS Research Plan, Vol.
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From page 73... ...
The NCS has the capacity to provide critical new information about risk factors (intrapersonal and environmental) and development sequelae of childhood injuries.
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From page 74... ...
The third hypothesis -- antecedents and resilience to traumatic life events in childhood -- seems almost only metaphorically linked to the injury section of the NCS research plan; perhaps conceptually reflecting on response to trauma. The hypothesis focuses primarily on anxiety disorders and the child's response to cumulative exposures to potentially traumatic events -- primarily influential life events, but also including physical abuse and injury exposures.
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From page 75... ...
The NCS proposals for the measurement of home and community environments are not well articulated -- an issue that is important for other research topics as well (see section on "Exposure Measures" below)
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From page 76... ...
The NCS research plan selects several conditions to illustrate the effects of HAAs: hypospadias, hypothyroidism, obesity, early (and late) onset of puberty in girls, and polycystic ovary syndrome.
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From page 77... ...
For most outcomes, the NCS research plan notes that only half the sample can be used (either male or female) , thus reducing power, and prevalence may be lower depending on the ethnic group.
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From page 78... ...
, psychosocial exposures, biological exposures, and genetic markers. (See NCS Research Plan, Vol.
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From page 79... ...
may well require too much interviewing time relative to their analytic value, but wages and work hours questions modeled after the CPS should probably be asked about the week prior to each interview. In addition to employment status, work hours, and wages, the research plan should include occupation.
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From page 80... ...
Chemical Exposure Measures As described in the research plan, the primary purpose of the NCS exposure assessment is to enable the epidemiological analysis of associations between priority exposures and priority outcomes that are described in the study hypotheses. The study will archive environmental chemical (and biological)
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From page 81... ...
Figure 9-1 in the research plan (NCS Research Plan, Vol.
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From page 82... ...
The research plan needs to provide further specificity on the assessment of POC exposure, including the use of dust samples and the timing of collection. In Table 9-1 (NCS Research Plan, Vol.
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From page 83... ...
The NCS notes that water and soil samples for pesticides will be collected only in rural areas, yet there are data showing high levels of indoor pesticides in urban areas, specifically in public housing and apartment complexes due to the use of insecticides for pest control. The research plan states (NCS Research Plan, Vol.
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From page 84... ...
The research plan states that biomonitoring has a limited role for assessing exposure to air pollutants. Yet urine samples are often used to measure exposure to some of the metals found in ambient particles, and an aliquot of urine could be archived for potential measurement of metals relevant to ambient air pollution exposure.
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From page 85... ...
. Some exposure measures are currently not interpretable as to the level of potential risk.
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From page 86... ...
Methodological Concerns Currently, the NCS research plan fails to acknowledge any critical or sensitive periods during which children's health and development may be most vulnerable to exposure to specific housing and community factors. Hypotheses regarding such periods would provide opportunities to test for their presence and effects.
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From page 87... ...
The goal should be a set of measures and data collection plans that are optimal with regard to analytic utility and response burden. Psychosocial Exposure Measures The NCS research plan proposes to collect information on an exceedingly diverse set of psychosocial exposure measures, including family process measures, such as the home environment and domestic violence; maternal mental health measures, such as depression; psychosocial stress measures, such as perceived chronic stress; social support; health behaviors, such as smoking; and features of child care.
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From page 88... ...
Rather we call for a careful elucidation of the choices made with specific reference to goals, hypotheses, and relevant outcome measures. Relating Exposure Measures to Outcome Measures The panel thinks that the best way to make decisions about what psychosocial exposure methods to collect rests on a refinement and focusing of the domains of interest in terms of outcomes.
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From page 89... ...
The NCS, in turn, can benefit from the development of high-quality, easily administered assessments that can be used to replicate its findings in other studies. Recommendations Recommendation 3-12: The NCS should reconsider its psychoso cial measures to ensure that they will provide high-quality data for outcomes of interest for child health and development.
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From page 90... ...
Interest in maternal glucose metabolism in pregnancy is driven primarily by its potential effect on birth defects and child obesity. However,
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From page 91... ...
Likewise, the research plan notes that the only endocrine measures of interest are maternal thyroid function during pregnancy and cortisol levels in the mother and infant at various times. With regard to the former, it should be noted that child hypothyroidism may be a mechanism for the linkage between hormonally active agents and reproductive outcomes, so it is not clear why only maternal thyroid function is of interest.
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From page 92... ...
Genetic Measures Each project outlined in the NCS research plan includes investigation of how genetic variation contributes to variation in risk of the study's key outcomes, ranging from childhood obesity to neurobehavioral traits. With advances in high-throughput genotyping technologies, it is now possible to directly measure hundreds of differences in particular genes and millions of mutations in the whole genome of large numbers of individuals to elucidate the genetic contributions to a human trait or disease.
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From page 93... ...
. In the current NCS research plan, the strategy for investigating genetic associations appears to lack an appreciation of the more rigorous standards
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From page 94... ...
for children if a genetic marker of a trait, say ADHD, is identified in the NCS, there must be a mechanism in place for validation at both the population and molecular levels to avoid the reporting of false results, many of which have already flooded the literature and mass media from other sources. Gene-Environment Interactions A major strength of the NCS research plan is its emphasis on geneenvironment interactions.
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From page 95... ...
This is a major oversight and an inconsistency between the neurodevelopment analysis plan (NCS Research Plan, Vol.
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From page 96... ...
This is not well articulated in the research plan, yet it is the study's greatest strength in this field. Recommendations Recommendation 3-15: The NCS should adopt a clear mechanism by which genetic association studies are internally and, optimally, externally validated before any results are published or released to the media.
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From page 97... ...
The NCS research plan proposes to pay some attention to child care, schools, and religious institutions in the revised section on child health and development, but it is not clear that attention to such issues will also inform other outcomes (e.g., schools as a source of environmental exposures for asthma and as a factor in diets leading to obesity)
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From page 98... ...
Since interesting policy variation will arise in states, counties, cities, and even neighborhoods, analysts conducting these kinds of policy analyses will need to be able to match detailed information on policies to the geographic location of respondents. Additional Exposures That Could Be Studied Through Data Linkage A major potential benefit of the NCS household-based sample design is that a wide range of exposure measures can be obtained by matching existing and future sources of environmental information to respondents' residential addresses.
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From page 99... ...
Recommendation 3-18: To facilitate linkages of NCS data with environmental exposures from other databases, such as measures of demographics, crime, government programs, and pollution, the NCS should develop a plan for geocoding the residential addresses from prebirth through adulthood of all participating children to
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From page 100... ...
Such arrangements must safeguard the confidentiality of NCS respondents.
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