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Introduction

The National Children’s Study (NCS) was congressionally mandated by the Children’s Health Act of 2000. Section 1004 focuses on the National Children’s Study stating, “it is the purpose of this section to authorize the National Institute of Child Health and Human Development (NICHD)1 to conduct a national longitudinal study of environmental influences (including physical, chemical, biological, and psychosocial) on children’s health and development.”2

The NICHD Office of the Director has primary responsibility for planning and coordinating the National Children’s Study, the largest (100,000 children) and longest (before birth to age 21) study of environmental effects on children’s health ever conducted in the United States. The NCS will examine the effects of the environment, broadly defined to include factors such as air, water, diet, noise, family dynamics, community and cultural influences, and genetics, on the growth, development, and health of children across the United States, following them from before birth until age 21. The goal of the study is to improve the health and well-being of children and contribute to understanding the role various factors have on health and disease.

Between 2005 and 2007, the research plan for the NCS was developed in collaboration among the Interagency Coordinating Committee, the

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1Congress passed Public Law 110-154 on December 21, 2007, renaming the Institute the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

2Children’s Health Act of 2000, Public Law 106-310, 114 Stat. 1101.



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1 Introduction T he National Children’s Study (NCS) was congressionally mandated by the Children’s Health Act of 2000. Section 1004 focuses on the National Children’s Study stating, “it is the purpose of this section to authorize the National Institute of Child Health and Human Devel- opment (NICHD)1 to conduct a national longitudinal study of environ­ mental influences (including physical, chemical, biological, and psycho- social) on children’s health and development.”2 The NICHD Office of the Director has primary responsibility for plan- ning and coordinating the National Children’s Study, the largest (100,000 children) and longest (before birth to age 21) study of environmental effects on children’s health ever conducted in the United States. The NCS will examine the effects of the environment, broadly defined to include factors such as air, water, diet, noise, family dynamics, community and cultural influences, and genetics, on the growth, development, and health of children across the United States, following them from before birth until age 21. The goal of the study is to improve the health and well-being of children and contribute to understanding the role various factors have on health and disease. Between 2005 and 2007, the research plan for the NCS was developed in collaboration among the Interagency Coordinating Committee, the 1Congress passed Public Law 110-154 on December 21, 2007, renaming the Institute the Eunice Kennedy Shriver National Institute of Child Health and Human Development. 2Children’s Health Act of 2000, Public Law 106-310, 114 Stat. 1101. 1

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2 DESIGN OF THE NATIONAL CHILDREN’S STUDY NCS Advisory Committee, the NCS Program Office, Westat, the Vanguard ­ Center principal investigators, and federal scientists.3 A review of this plan can be found in National Research Council (NRC) and Institute of Medi- cine (IOM) (2008). The current design uses a separate pilot (or “­ anguard V Study”) to assess quality of scientific output, logistics, and operations and a “Main Study” to examine exposure-outcome relationships. The house-to-house recruitment strategy endorsed with qualifications by the 2008 panel of the NRC/IOM was tested in the Vanguard sites, result- ing in recruitment of fewer pregnant women and births than originally estimated. The issues associated with sampling were further studied in the additional Vanguard sites. As the results from Vanguard sites became available, there was much discussion about the most effective sampling approach among the NCS Program Office, federal and non-federal sam- pling experts, Vanguard principal investigators, and ­ thers. Considering o this input, the NCS proposed the use of a multilayered cohort approach for the Main Study, which was one of the topics for discussion at the workshop that is the subject of this publication. In the fall of 2012, NICHD requested that the Committee on National Statistics (CNSTAT) of the NRC and the IOM convene a joint workshop, to be led by CNSTAT. The statement of task was as follows: An ad hoc steering committee will organize a public workshop on issues related to the overall design (including the sample design, participant recruitment, and framework for implementation) of the congressionally mandated National Chil- dren’s Study (NCS). The NCS is intended to follow a cohort of children identified at or before birth through age 21 years. The study consists of a pilot or Vanguard Study, currently under way, focused on the feasibility, acceptability, and cost of study implementation and logistics to run in advance of, and parallel to, a Main Study. Based on Vanguard Study experience to date, the National Institute of Child Health and Human Development (NICHD) is proposing a multilayered approach to enrollment, using a national probability sample of hospitals and birthing centers for a birth cohort, supplemented with additional cohorts of pregnant women and pre- conception women, as well as special samples of population groups that may be underrepresented in the main cohorts. NICHD will provide a background document on the proposed design that will be discussed by workshop participants. The com- mittee will develop the agenda for the workshop, select and invite speakers and discussants, and moderate the discussion. Following the workshop, a designated rapporteur will prepare an individually authored summary of the presentations and discussion. NICHD will also be provided with a verbatim transcript of the event. 3The National Children’s Study has a website with a wealth of information concern- ing the history of the study and the activities that are under way. See http://www.­ nationalchildrensstudy.gov/Pages/default.aspx [June 2013].

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INTRODUCTION 3 In preparation for the workshop, NCS provided a background paper to the steering committee (National Children’s Study, 2012).4 The steering committee, collaborating by email and telephone, discussed the paper and the challenges to be addressed at the workshop, determined the agenda, and selected potential speakers. In addition, NCS and CNSTAT collaborated on the preparation of a more abbreviated workshop back- ground paper that was distributed via the CNSTAT website in advance to all meeting attendees. The paper was referred to during the workshop as the Background Paper (and is cited in this publication as Kwan et al., 2013). The purpose of Kwan et al. (2013) was to explain the NCS and the status of the program and to pose specific questions for consideration at the workshop. The Workshop on Design of the National Children’s Study Main Study took place at the National Academy of Sciences on January 11, 2013. The three main topics addressed at the workshop were the collection of environmental exposure measures, the distribution of the sample among cohorts, and statistical issues associated with the sample design. These discussions, as outlined in Kwan et al. (2013), were intended to inform the NCS Program Office on specific design questions to guide the NCS Main Study, including considerations related to prenatal exposures, alternative approaches for collecting information, costs of such collections, and their value to analysis. The workshop was organized around four sessions, each with a specific set of questions to discuss. (The workshop agenda can be found in Appendix A, and a list of workshop registrants can be found in Appendix B.) Each of the following four chapters is dedicated to one of the work- shop sessions. The chapters begin with the information about the topic provided in Kwan et al. (2013) and the detailed questions posed by NCS. The chapters then summarize the main points of the panelists’ remarks and the ensuing discussions. The overarching questions from Kwan et al. (2013) covered in each chapter are as follows: • Chapter 2: Given the challenge as stated in the Children’s Health Act of 2000 to “perform complete assessments of environmental influ- ences on children’s well-being,” does the proposed visit schedule and sample collection balance the complex requirements? 4In addition to this paper, the NCS homepage for the NAS Workshop has links to the workshop agenda, the transcript, and many other background resources. See http:// www.nationalchildrensstudy.gov/research/workshops/Pages/nationalacademyofsciences workshop.aspx [June 2013]. The white paper for the steering committee is titled The ­National Children’s Study Institute of Medicine Workshop Steering Committee Briefing Document. The back- ground paper for workshop participants is titled Background for Discussion at the Workshop on the Design of the National Children’s Study.

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4 DESIGN OF THE NATIONAL CHILDREN’S STUDY • Chapter 3: What should be the criteria for the cohort allocation decision and what evidence is available to support an assessment of each criterion? What should be the allocation of sample cases among the vari- ous cohorts? • Chapter 4: Given the study design proposal described in Kwan et al. (2013), and using the example cohort proportions proposed in the Chapter 3 questions, what enhancements can be made to address estima- tion and imputation challenges? • Chapter 5: From today’s discussion, can you synthesize the trade- offs among factors, issues, and values that need to be balanced and con- sidered by NCS leadership? This report was prepared by a rapporteur as a factual summary of what occurred at the workshop. The steering committee’s role was limited to planning and convening the workshop. The views contained in the report are those of individual workshop participants and do not necessarily represent the views of all workshop participants, the steer- ing committee, or the National Research Council/Institute of Medicine.