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Family history studies are now used for a much wider range of purposes than in the past. This chapter discusses their usefulness for refining phenotype definitions, targeting preventive interventions, characterizing genetic effects, and exploring gene-environment interaction. These are in addition to their original role in genetic research, which was to examine whether diseases aggregate in families. The chapter also elaborates on their relationship to the risk factor designs described in previous chapters.

This chapter gives an account of family studies of intellectual abilities in adulthood designed to consider similarities in adult parent-offspring and sibling pairs as well as similarity in married couples. Of particular interest is new material on changes in the rate of cognitive change across biologically related generations. Married couples were studied for as long as twenty-one years. They showed significant initial within-couple correlations on verbal meaning, inductive reasoning, and word fluency, and social responsibility, and on the Index of Educational Aptitude, even when age and education were controlled. Spousal similarity increased by length of marriage on verbal meaning, and attitudinal flexibility, and on the Index of Intellectual Ability.

This chapter further places religious leaders’ enthusiasm for eugenics in the context of both Progressivism and the Social Gospel movement. As eugenic ideas gained in popularity, religious leaders such as Rev. Walter Taylor Sumner, a Protestant Episcopal Dean in Chicago, began crafting their own eugenic proposals, which they administered in their churches. Dean Sumner’s eugenic “marriage health certificate” plan garnered publicity and many imitators. This chapter describes such proposals and places them in the context of the growing social service movement in the Protestant churches in particular, and the public’s increasing interest in eugenics in general. It also discusses the many “eugenic family studies” published in the 1910s.

This chapter reviews some of the key family-based studies that have identified links between various illnesses and behaviours in parents and siblings with psychiatric disorders in study members. It also describes how sibling and twin studies are beginning to produce results that quantify the relative contribution of genetic and environmental effects. The chapter concludes with recommendations from the perspective of life course epidemiology to move beyond the established associations and to increase our understanding of the underlying mechanisms involved in psychiatric disorders. Specifically, it describes the range of characteristics in terms of study design, and type and scope of data that should be incorporated in future large population based studies.

Family-based studies can provide a more comprehensive view of life course epidemiology than studies that do not engage with family effects. They can establish intergenerational associations, help to understand the influence that one family member can have on the health and wellbeing of another family member and they can help to unravel the mechanisms behind the relationships of genetic, social, and environmental factors that impact on health at different life stages. This chapter summarizes the common threads across the previous chapters and highlights the key methodological challenges and opportunities of using family study designs in life course epidemiology. It discusses a number of points, including some that receive less attention in the preceding chapters, that are felt to be important for the future direction of research using family-based studies in life course epidemiology.

This chapter briefly describes the growing impact of non-communicable disease in low- and middle-income countries (LMIC) which, together with existing infectious illnesses and a rising incidence of violence, represents a triple health burden. Birth cohort studies, and in particular those with family-based elements, clearly have a role in identifying risk factors for chronic disease. Existing studies from LMIC are described. The chapter advances a number of reasons for adding to the very sparse research base outside of industrialized nations, and attempts to provide solutions for some of the methodological complications that might accompany such endeavours.

In life course epidemiology studies, the use of proxy (secondary) respondents may be an integral part of the study design or a consequence of not being able to reach or obtain information from the index subject. Based on the available evidence, the main factors that increase validity and reliability of proxy responses are broad categorization of, and focus on, directly observable characteristics and behaviours; questions requiring a binary response; recent characteristics and behaviours; face to face interviews; spouse/partner selected as proxy. Certain issues remain unaddressed by the available literature, including subject areas such as diet, the choice of proxy beyond spouse/partner, validation of responses when the index is unavailable and the effect of index characteristics on proxy responses. Finally, practical tips are presented in this chapter from a case study that successfully employed proxy respondents.

Siblings can have a great deal in common (e.g., parents, genes, early life home env1ironments, etc.), but they are also distinct individuals with unique personalities and physical traits. This chapter discusses how researchers can use similarities and differences across siblings to investigate questions of life course epidemiology. First, it discusses how sibling fixed effects models may help deal with residual confounding from unobserved family-level factors. Second, it discusses how behavioural genetics approaches can help unravel genetic heritability from environmental determinants of health. Finally, it explains genetic linkage studies in which researchers use siblings' DNA information to learn more about the effects of chromosomal regions and genes. When considering each of these strategies, the chapter reviews the relevant literature and discusses the strengths and weaknesses of the particular methods.

This chapter discusses issues concerned with the design and practicalities of setting up birth cohorts for life course epidemiology. The demand for a blueprint of the ideal birth cohort study is perhaps intuitive, but the chapter questions the extent to which standardization of data collection and study protocols across contemporary and planned birth cohorts is desirable or feasible. The chapter discusses different approaches, difficulties and strengths of these different approaches, the determination of scientific priorities, definition of the birth cohort (including which family members are key participants), data collection and samples size, as well as the ethical considerations specific to the establishment of a birth cohort. The advantages of a scientific focus on specific exposures in each birth cohort study, of documentation of birth cohort data, and of collaborative studies using data from several birth cohorts are emphasized.

Intergenerational data necessarily reflect the time and place that the different generations of participants were living in. This chapter aims first to introduce simple concepts to provide an understanding of the founding assumptions and principles, before moving on to more complex analytic methods. As the objectives of analyses may vary substantially across intergenerational studies, there is no easy guideline for analyses, except perhaps that some a priori clarity on the main associations of interest is crucial. Since parents and their offspring are genetically related, intergenerational studies are to some extent genetically informative even if no genotyping was performed. Much of the analyses are concerned with identifying or unravelling the relationship between outcomes and genetic and environmental factors. Ways of handling missing data as well as approaches to deal with non-paternity are also discussed. Illustrative examples are drawn from the two cohort studies.

The three chapters in this section offer different but complementary conceptualizations of ‘family’. Morton and Rich Edwards used ‘family’ to document inter-generational concordance of reproductive outcomes, Hatch and Mishra documented how ‘family’ could be characterized as a risk exposure for later poor mental health, and Lawlor and Leon used ‘family’ as a means to control for unmeasured confounding by family characteristics to better understand causal mechanisms relating fetal growth to later disease. Lawlor and Leon's approach is similar to that used in studies examining the possible intrauterine origins of birth weight and cognitive ability and this chapter briefly explores that literature. Families surely matter for better understanding individual and population patterns of ill-health.

Family characteristics and interactions can directly affect one's health and wellbeing across the life course. In addition to the importance of recruiting and collecting data on family members, including parents, grand-parents, and siblings, for understanding fully the determinants of health and well-being across the life course, family studies (for example, intergenerational, sibling, twin) can help assess causality and underlying mechanisms in life course epidemiology. In this introductory chapter a brief background to the importance of family based studies to life course epidemiology is provided, followed-by a summary of the structure of the book and its overall aims.

Chapters 2 to 4 describe three specific approaches to family studies, namely, intergenerational, sibling, and twin studies. All can be used to assist in distinguishing between genetic and environmental influences mainly within the classical nature-nurture paradigm. This chapter summarizes the three approaches, describes links across the methods, and draws on other examples to highlight some of the areas discussed and to explore other issues, such as birth order effects. All three chapters use the example of influences on birth weight to exemplify the use of their specific study types, intergenerational, sibling or twin, but they also consider outcomes occurring later in the life course. As in all branches of epidemiology a variety of methods in different contexts is required for us to see consistent patterns emerge. Conflicting evidence points to our lack of understanding and for alternative hypotheses to be explored.

This chapter summarizes the origins of some of the existing life course studies and the current potential for using these studies to address family-based life course questions. It also highlights important methodological and practical issues for the future conduct of such studies. It has to be considered carefully whether it is worth collecting more prior generation and/or offspring generation data in these established cohorts given the practical difficulties and costs associated with such an undertaking as detailed Chapters 6, 7, and 8. The chapter concludes that there is a growing need to build infrastructure across cohort studies to encourage and support collaborative research. It is also clear that there is a great need to value and support the lifelong volunteers and the researchers who initiate and run longitudinal studies in order to realise the full scientific potential of life course research.

This chapter summarizes some of the issues that have been described in the previous two chapters on statistical considerations in family studies. It highlights some of the assumptions underlying the analytic methods and discusses how their use can impact the results. The statistical analyses outlined in this section share common features aimed at quantifying the association between genetic and environmental factors with phenotypic outcomes. For some research, the focus is on heritability while for other work, the focus is on environmental issues while controlling for genetic influences. Modelling approaches for each are discussed, emphasizing potential problems and providing guidelines for careful interpretation. Examples from published empirical epidemiological work is used to illustrate the breadth of analytical strategies adopted for family studies research.

This chapter begins with a discussion of Mendelian versus complex (non-Mendelian) neurological disorders, followed by an overview of the structure of DNA and the molecular basis of disease. It considers the methods of genetic epidemiology, differentiating family-based studies from population-based studies of unaffected individuals. The options for genetic epidemiology study designs are presented, with a discussion of strengths and limitations of each approach. Recent technological developments are discussed, as are the important ethical and social implications of genetic epidemiologic research in the study of neurological disorders.

There is good evidence that associations exist between fetal and other early life factors and subsequent risk of cardiovascular disease (CVD) that can be replicated in a range of settings. These associations provide the evidential basis for the developmental origin of CVD in humans, which posits that susceptibility to CVD in later life is importantly influenced by the nature of the in utero, infant, and childhood environment. However, much of this evidence is from cohort studies of unrelated individuals, and it has been argued that these associations may be explained by confounding by genetic variation or uncontrolled aspects of the environment. This chapter describes how family-based studies, including twin, sibling, and intergenerational studies demonstrate the potential of family-based studies in throwing light on the developmental origins of CVD.

This conclusion summarizes the key arguments of the book, including the many assumptions it challenges about the history of eugenics and the history of American religious leaders in the early half of the 20th century. It is clear that American religious leaders embraced eugenics when they departed from the traditional tenets of their faith, and that they did so in an effort to find new methods of social reform to suit a time of often-bewildering social and cultural change. This chapter also ties the history of eugenics to current debates in bioethics, revealing the continuities and discontinuities in hereditarian thinking from the previous century into the present. It is argued that the peculiar history of eugenics in the United States in the early-to-mid 20th century has fundamentally shaped the way genetic technologies is discussed in the twenty-first century. An understanding of that history — particularly the history of the ethical and theological debates that occurred — is necessary as we enter a new era of genetic science.

This chapter reflects on the shifting public discourses in Britain concerning mothers and the labour market from the end of the Second World War and shows how the framing of research questions reflects these changing public discourses. At the end of the Second World War, women were ejected from many of the jobs in which they had worked in wartime to create work for returning servicemen. This ejection marked a watershed in women's lives and a backward step in female emancipation. The author began research on mothers in the labour market in the late 1970s. At that time, home was still promoted as the ‘best place’ to rear young children and mothers the best people to do so. This narrative shifted in the late 1980s, reflecting not only the rapid growth in the employment of mothers with young children but the increased emphasis placed by government on market forces and the notion of ‘individual choice’. Reflecting these changes, the social research agenda also shifted. In the 1960s and 1970s, motherhood was a small field of inquiry occupied mainly by those concerned with family life or child development. Gradually, much of the territory of ‘family studies’ was taken over by feminist sociologists whose work threw the spotlight on to patriarchy and women's oppression.