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The research team have several acknowledgements to make. First, they would like to thank the advisory group for their support and assistance with the scoping review. The advisory group were Prof. Richard Layte (Trinity College Dublin), Prof. Dermot O’Reilly (Queens University Belfast), Dr. Orla McBride (Ulster University), and Prof. Lisa Calderwood (University College London). Second, the research team express their sincere thanks to the participants in the stakeholder consultation who freely gave their time to discuss the context surrounding a potential new Growing Up in Ireland birth cohort. Third, the research team thank the study teams who communicated with them about their cohort studies featured in this scoping review. Finally, the research team would like to acknowledge the intellectual, creative, and editorial contributions of the Department for Children, Equality, Disability, Integration, and Youth; especially Anna Visser and Claire Farrell. The quality of this Scoping Review is testament to the involvement of all people who contributed across sectors.

1.1 Introduction

The health and well-being of adults is established in early life. A nationally representative birth cohort study that begins during pregnancy or from birth has a unique value in understanding the health and well-being processes of children into adulthood (Canova & Cantarutti, 2020; Golding, 2009). The Growing Up in Ireland (GUI) national longitudinal study has to date played an important role in understanding the varied lives of children in Ireland.
This scoping review will assess the scope of a potential new GUI birth cohort by examining developments across key domains of data collection and analysis for longitudinal birth cohort studies, in addition to exploring relevant health, socioeconomic and environmental factors across the life course of the next cohort of children in Ireland. Significant social, economic and policy changes have occurred in Ireland (e.g. population composition, healthcare, education, labour market) since the beginning of the GUI birth cohort study in 2008/2009. Recent policy changes also include those brought about by the COVID-19 pandemic and the war in Ukraine.

1.2 Chapter overview

This chapter will begin with an overview of the background to longitudinal birth cohort studies and how they can help establish causal links between exposures and outcomes. This overview will then lead into a literature review to synthesise the conceptual frameworks used in birth cohort studies, providing a synopsis of a range of study objectives across multiple international birth cohort studies. The selection process used to determine the four named birth cohort studies to serve as case studies is outlined. These cases are the Millennium Cohort Study (MCS), the Danish National Birth Cohort (DNBC), Étude Longitudinale Française depuis l’Enfance (ELFE), and Generation Victoria (GenV). Each case study is then addressed with respect to the study background, rationale, aims and objectives, conceptual framework, main study domains, and sampling framework. However, more detailed discussions of the data collection methods, study designs (including attrition), and data access and analysis are provided in Chapters 2, 3 and 4, respectively. The Early Life Cohort Feasibility Study (ELC-FS) and the Growing Up In Digital Europe (GUIDE) study are then discussed, although not as named case studies for the purpose of this review. The ELC-FS is a new United Kingdom (UK)-based birth cohort study that will offer valuable insights into a range of learnings to benefit future birth cohort study research teams. GUIDE is Europe’s first cross-country comparative birth cohort study. Finally, a discussion of the strengths and limitations of study conceptual frameworks concludes this chapter, keeping in mind the GUI ’08 study as the ‘foundation case’.

1.3 Background to longitudinal birth cohort studies

Infancy and childhood are critical life phases typified by rapid growth and development processes which influence health and well-being across the life span. Early-life exposures, including nutritional, environmental, and socioeconomic factors, can affect optimal growth and development from prenatal stages and throughout the life span (Larsen et al., 2013; Lawlor, Andersen & Batty, 2009; Lynch & Smith, 2005). Broader political, societal, and cultural contexts also affect infancy and early childhood development phases (Black et al., 2017; Maggi et al., 2010). Longitudinal birth cohort studies have contributed substantially to increasing scientific knowledge about prenatal, childhood, and life course health outcomes (Orri et al., 2020; Ji et al., 2019; Thompson et al., 2010; Golding, 2009; Burke et al., 2005). Birth cohorts can also shed light on socioeconomic, racial and ethnic, and other structural disparities across a range of social, health, and economic outcomes (Cotter et al., 2019; Kent & Pitsia, 2018; McCrory et al., 2017; Watson et al., 2014; Kelly, Becares & Nazroo, 2013; Sullivan, Ketende & Joshi, 2013).
Longitudinal birth cohort studies are prospective studies which follow the same cohort of participants over time from birth. Multiple domains of data are collected to provide insights into the complex processes and outcomes across participants’ lives (Canova & Cantarutti, 2020; de Groot et al., 2017). Prospective designs are key to explaining and understanding the causal direction of an association by enabling the identification of predictors and a range of factors (both risk and protective) that are associated with outcomes and/or trajectories/pathways over time (Richmond et al., 2014). From a social health perspective, longitudinal data can help uncover the cause and effect of inherited and life course influences on childhood health, and the development of common and complex health issues into adulthood. While many birth cohort studies are epidemiologically oriented, many recent birth cohort studies (such as the MCS, Growing Up in Scotland, Growing Up in New Zealand, and Growing Up in Australia: The Longitudinal Study of Australian Children [LSAC]) study the interplay of factors across multiple domains. Furthermore, the long-term follow-up period in birth cohort studies makes them valuable tools to address new policy-related questions and influence policy development (Checkoway, Pearce & Kriebel, 2007). Birth cohort studies can also assess the impact of policy changes over time. For example, children in the GUI study were among the first to be eligible for a subsidised preschool place arranged through the Early Childhood Care and Education scheme (Smyth, 2018). This allowed for the assessment of this new policy regarding take-up and the multiple effects of centre-based care on children.
Since birth cohort studies follow the same individuals over time, they can help establish causal links between exposures and outcomes. Exposures and events in the pre- and postnatal periods and infancy can result in long-term consequences for health and well-being into adulthood. For example, prenatal development and birth outcomes can be influenced by maternal diet, drug use, smoking, and alcohol intake (Heude et al., 2016: Lawlor, Andersen & Batty, 2009). Early life factors and exposures have been associated with cardiovascular disease, cancer, asthma, other respiratory diseases, allergies, cognitive ability and degeneration, socio-emotional function, and mental health (Mitku et al., 2021; Blane et al., 2013; Hanson & Gluckman, 2011; Gluckman et al., 2008). Exposure to poverty and/or material deprivation are additional risk factors for poor health in childhood (Marmot & Wilkinson, 2005).

1.4 Literature review of core conceptual frameworks and study objectives

1.4.1 Overview of conceptual frameworks for longitudinal birth cohort studies

Conceptual frameworks underpin research by providing a set of definitions or approaches to follow (Corna, 2013). Used frequently in social, health and behavioural science research, conceptual frameworks include one or more theories and concepts to illustrate causal pathways and relationships, and how they map onto the observational or interventional studies being undertaken. In social and health-focused research, conceptual frameworks guide intervention studies and offer insights into how to approach reducing disparities (Ridgeway et al., 2017).
Longitudinal birth cohort studies often employ conceptual frameworks based on life course models (Jones et al., 2019; Kuh et al., 2003). Life course conceptual frameworks are interdisciplinary and are used in the domains of sociology, biology, psychology, anthropology, economics, and epidemiology (Jones et al., 2019; Kuh et al., 2003). These frameworks guide understanding of the short- and long-term effects of a myriad of social, health and economic factors which are affected by a range of exposures and determinants from conception to death (Jones et al., 2019). These range from biomedical, socioeconomic, and psychosocial factors to environmental factors at macro, meso, and micro levels, and take period effects taken into consideration (e.g. children born at the end of the 1990s in comparison with children born in the 2000s) (Greene et al., 2010a; Kelly et al., 2009).
Wang et al. (2021) reviewed a comprehensive range of conceptual frameworks used by early life cohort studies worldwide. The purpose of this review was to inform the selection and development of a relevant life course framework to guide the content selection and visual communication design for the GenV study. GenV is a new longitudinal research programme based in Victoria, Australia. This health-focused, large-scale cohort study aims to examine and address complex health issues affecting children from birth to adulthood (Davies et al., 2020). GenV will follow a cohort of children born in Victoria between mid-2021 and mid-2023. The comprehensive range of frameworks identified by Wang et al. (2021) are summarised in Table 1.1. The conceptual frameworks used in the selected case studies for this report are discussed later in this chapter (see Section 1.4 for further detail).