The National Children's Study Research Plan A Review (2008) / Chapter Skim
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2 NCS Goals, Conceptual Framework, and Core Hypotheses
2 NCS Goals, Conceptual Framework, and Core Hypotheses
Pages 23-52
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From page 23... ...
This chapter provides an overview of the NCS design to orient the reader and convey a sense of the large scale and scope of the effort; it then presents and comments in broad terms on the NCS goals, conceptual framework, and selection of core hypotheses as outlined in the research plan (NCS Research Plan, Vol.
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At the same time, we note -- as does the NCS research plan itself -- the opportunity afforded by the study's length to alter course in one manner or another as appropriate, not only to take account of our comments, but also to take advantage of relevant new measurement techniques and research insights. DESIGN IN BRIEF The NCS is designed to be a long-running, observational panel study of a nationally representative probability sample of 100,000 births to be followed from before birth to age 21.
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During the preparation and initial sampling phases, the 35 to 40 study centers that will ultimately be part of the NCS operation will engage in outreach activities to inform local communities of the study and encourage participation (see NCS Research Plan, Vol.
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26 TABLE 2-1 Planned NCS Data Collection from Prebirth Through 24 Months After Birth Type and Time of Biologic Clinical/Developmental Environmental Contact Questionnaire and Diary Samples Examination Samples Prepregnancy Maternal contact only (unless otherwise noted) Home visit–interview Demographics Blood Anthropometrics Indoor air Household composition Urine Blood pressure House dust Medication use Saliva Health behaviors Vaginal swabs Housing characteristics Hair Chemical exposures Product use Occupational exposures Diet Phone follow-up Diet -- -- -- -- -- - Chemical exposures
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Saliva Fetal ultrasound (from medical Drinking water Health behaviors* Vaginal swabs report or clinic visit)
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contact Birth: At delivery, Health behaviors (M) Blood (M)
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9-month phone call Child care Medical update (C) -- -- -- -- -- - Housing update Chemical and occupational exposures (M, C)
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Tobacco use Cognition (if not assessed at first trimester meeting) 18-month phone call Child care Medical update (C)
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Source: NCS Research Plan, Vol. 1, Tables 6-2 through 6-4.
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From page 32... ...
Topics covered in interviews at one or more points in time include household composition; housing characteristics; maternal (or primary caregiver) characteristics (demographics, medication use, health behaviors, chemical exposures, product use, diet, medical history, stress and social support, depression and cognition, occupational exposures, child care)
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From page 33... ...
The primary aim of the NCS is to investigate the separate and combined effects of environmental exposures (chemical, biological, physical, and psychosocial) , as well as gene-environment interactions, on pregnancy outcomes, child health and development, and precursors of adult disease.
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From page 34... ...
Here we draw a conclusion about two major strengths of the NCS design, which are the large, nationally representative, equal probability sample design and the large numbers of variables to be collected on both outcomes and exposures over a long period of time. We draw another conclusion about four overall weaknesses of the NCS design, which are an inadequate plan for understanding health disparities, inadequate conceptualization of health and development and an overemphasis on disease and impairment, constraints on the study's ability to measure chronic and intermittent exposures, and challenges to data quality.
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From page 35... ...
Conclusion 2-3: In four overarching areas, the NCS design, as repre sented in the research plan, is not, or may not be, optimal for achieving the goals of the Children's Health Act. These areas are: • insufficient attention to understanding disparities in child health and development among population groups of children defined by race, ethnicity, language, socioeconomic status, and geo graphic area, which the act explicitly mandates; • inadequate conceptualization of important constructs, including health and development, and an overemphasis on disease and impairment relative to health and functionality and on risk fac tors relative to protective health-promoting factors; • impaired data collection schedules and types of measures to sup port evaluation of some of the effects of chronic and intermittent exposures on child health and development; and • underappreciation of the challenges to obtaining the highest possible quality of data from an observational design, which include the decentralized data collection structure of the study and limitations on the frequency of home and clinic visits and on the collection of medical and other administrative records for study participants.
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From page 36... ...
On balance, we support the sample design adopted by the NCS given its resource constraints (see Chapter 4) , although -- as noted below and elsewhere in the report -- we encourage the consideration of adjunct studies that provide additional sample for scientifically interesting groups when resources and respondent burdens permit.
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From page 37... ...
. Overall Weaknesses Health Disparities The Children's Health Act called for the proposed longitudinal study to "consider health disparities among children," and we understand that an early NCS working group considered issues of measuring health and developmental disparities among racial and ethnic groups, although any products from this group were not available on the NCS website.
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From page 38... ...
There are ways to accomplish this within the current NCS design -- for example, by encouraging appropriate adjunct studies that would develop hypotheses and carry out analyses of racial and ethnic disparities in child outcomes. Such studies could add sample for specific racial and ethnic groups and perhaps add data items, such as more extensive medical histories from provider records than currently planned (see further discussion in
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From page 39... ...
Recommendation 2-1: The NCS should give priority attention to seeking ways to bolster the ability of the study to contribute to un derstanding of health disparities among children in different racial, ethnic, and other population groups, including the reestablishment of a working group to oversee this area and the encouragement of appropriate adjunct studies. Concepts and Emphasis The NCS research plan is much stronger on disease, impairment, and the identification of risk factors for abnormal development than it is on health, functionality, and the identification of protective and positive factors for normal development.
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To ensure that sufficiently rich data are collected for important domains, we urge the NCS to do two things: first, to develop a richer conceptual framework than is presented in the research plan to guide the choice of hypotheses and specification of measures (see section below on "Conceptual Framework") and, second, to revisit each hypothesis to determine whether it is sufficiently compelling and clearly specified to retain in the study and, if so, whether adequate data are proposed for collection to permit appropriate analysis.
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From page 41... ...
For example, medical records will not cover children's health problems in cases in which treatment is not sought, and the recorded diagnosis or diagnoses may not accurately reflect the underlying pathologies for insurance coverage or other reasons. Nonetheless, relying almost exclusively on retrospective parental reports on medical conditions and treatments and on such sensitive topics as domestic violence or alcoholism and failing to collect records from service providers would seem to markedly impair the quality of the data for understanding child health and development.
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population, on which we comment in the previous section. It also provides a very simple conceptual model, in which environmental exposures in various domains are linked to outcomes in various domains with gene expression and health care as mediating factors (NCS Research Plan, Vol.
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Assessment We appreciate the acknowledgment in the NCS research plan of the complexity of child development and the complex ways in which myriad factors may interact to affect that development. However, we find the conceptual framework for the NCS to be less well developed than we would have expected for this stage of the project.
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From page 44... ...
. Such an approach would lead to more of a focus than is evident in the NCS research plan on factors that protect against adverse outcomes or that mitigate the effects of risk factors; on multiple factors affecting outcomes; and on the interplay of chronic illness and development for such specific conditions as asthma (see Hayes,
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From page 45... ...
develop the capacities that allow them to interact successfully with their biological, physical, and social environments. This definition draws upon an explanation from the World Health Organization that health is a state of complete physical, mental, and social well-being, not merely the absence of disease or infirmity; a collaborative effort of the European Union Health Monitoring Programme to develop the Child Health Indicators of Life and Development (CHILD)
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From page 46... ...
In choosing specific measures to include on the basis of the chosen framework, the NCS should consider -- in addition to, or in place of, those already proposed -- such indicators of child well-being and mental health as secure attachment relationships, social competence, cognitive development and achievement, optimism, and empathy. One can add to this list assessments of positive emotionality, healthy attributional style, ego-resilency, and many more.
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From page 47... ...
The NCS may want to consider the use of expert consultants to assist in the assessment and specification of appropriate frameworks, constructs, and measures to guide decisions on measures and the timing of assessments to be obtained in the study, with the Vanguard Centers used for pilot testing as recommended below. Recommendation 2-3: The NCS should clearly define the key con structs of child health and development and more fully develop a conceptual framework for understanding child health and develop ment over the life course of infancy, childhood, and adolescence.
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1, Sec. 4.2, Table 4-1; specific hypotheses in each of these areas are provided in Vol.
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In our view, the NCS design, as represented in the research plan, allows for the genesis of new research ideas and hypotheses in a number of ways, including the length and breadth of the data-gathering platform, the nationally representative, equal probability sampling design, the provision for substudies and adjunct studies, and the storage of biological and environmental specimens for later analysis. Nonetheless, the set of initial hypotheses that are developed to guide the study should be carefully selected and well framed to enable the study to collect the most appropriate outcome and exposure measures.
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Hypotheses are nearly missing altogether in the area of racial and ethnic disparities, as we noted above. The study will undoubtedly contribute to a better understanding of the sources of racial and ethnic, language, socioeconomic, and geographic differences in child health, but it has formed almost no hypotheses about these differences that could have informed the study design and made it more useful in this regard.
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USING THE VANGUARD CENTERS AS PILOTS An important shortcoming of the NCS, as currently planned, is the absence of a pilot phase for thorough testing, evaluation, and refinement of study concepts, measures, instruments, and procedures. The study design is complex in every aspect, from developing appropriate constructs, hypotheses, and measures of outcomes and exposures, to identifying and enrolling participants, maintaining a high response rate over the life of the study, administering the very large number of survey, clinical, and environmental sampling instruments, and managing very large databases to which many study centers have contributed.
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Throughout the life of the study, the NCS should use the Vanguard Centers to pilot test and experiment with data collection methods and instrumentation.
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