First, long-term studies that follow participants into adolescence and early adulthood are considered essential to assess the full range of developmental consequences of exposure to environmental chemicals.
It is also important to identify a population with a wide range of exposure concentrations for those key pollutants hypothesized a priori to be of interest in order to evaluate the relationships between the distributions of multiple exposures and observed effects.
It is necessary to allow for population differences in literacy, language, and culture when establishing study procedures for recruitment and retention and in determining the type of information collected and the methods of collection.
Assessment tools need to balance measures both broad and narrow in scope. Questionnaires, neurodevelopmental instruments, and the like employed in these studies should include a core set to evaluate the entire cohort and additional segments for selected populations that may be unique based on their exposure or other attributes.
Exposure assessment should include a combination of environmental and personal measurements as well as data derived from questionnaires and from observational and ecologic data. The exposure assessment effort should take advantage of modeling approaches to provide estimates for the entire cohort. Targeted exposure studies in a selected sub-sample of study subjects may be useful for improving exposure assessment. The depth of assessments that can be realistically implemented will be restricted in populations that are widely dispersed geographically, have limited transportation, or lack trained personnel in the community.
Procedures for monitoring the quality and accuracy of data collection must be established and maintained not only for the collection and analysis of biologic or environmental specimens, but also for the assessment of questionnaire, developmental testing, and other health outcome data. Data safety and monitoring procedures must be in place.
Active and meaningful participation of the community is essential for determining the relevant research questions, enrolling and retaining the cohort in an intensive investigation over the long term, and contributing to translation of scientific principles and research results for communities and the public at large. This requires establishing trust and respecting differences in culture and knowledge of the community. Sufficient time and resources are necessary to develop community partnerships.
The ethical issues in a longitudinal birth cohort study are likely to become increasingly more complex in the changing medical and legal environment and must be carefully considered in designing research protocols and following the cohort. It is necessary to develop clear plans of referral when children with disease, developmental difficulties, or adverse social situations emerge.
Communication of risk to participants and the community and translation of research findings into interventions and policies are of utmost importance and should be part of the research plan and cost consideration.
Funding for a longitudinal birth cohort study must be adequate for the start-up period, continuous without gaps, and long term. Costs have often been underestimated because tracking and maintaining study participants is labor intensive.
The unique characteristics at each developmental stage from birth through adulthood must be considered. Every age presents special challenges in both outcome and exposure assessment.
Finally, the health and development of children are multifactorially determined. The greatest challenge is anticipating the data and specimens that will allow the questions of the future to be answered. This requires state-of-the-art tools for data collection and tracking participants, environmental and biologic specimen repositories, and anticipation of future human subject requirements in consent procedures.
The unique challenges faced by the Children’s Centers in studying diverse populations will be especially helpful for the National Children’s Study, which is intended to be a nationwide study representative of the many populations across the United States. Although the Children’s Centers have reported important findings from their individual studies, it is only by examining the collective experiences of the Children’s Centers in these lessons learned articles that we gain a better perspective of the potential challenges to be met in the many National Children’s Study sites.