The long arm hypothesis: childhood poverty, epigenetic ageing, and late-life health in America, Britain, and Europe

Childhood conditions have been increasingly considered a risk factor for old age disability, dysfunction, disease and mortality. The term ‘long arm of childhood conditions’ was coined by Hayward and Gorman (2004) who studied the influence of childhood poverty on mortality in American males in their forties and fifties. Recently, nationally representative surveys or large cohort surveys have emerged to extend and provide empirical support to the long arm thesis . The new studies unpacked the outcome of mortality into various types of ill health and dysfunction, while simultaneously extending the age range to the ninth decade. Studies from Britain and Sweden, as well as other European countries, examined whether childhood poverty relates to general health, physical health, mental health, and cognitive health of people in their fifties and older. Not only were the health outcomes diverse, the definition of childhood poverty also varied. It is therefore necessary to examine the thesis with a common definition of childhood condition and comparable health outcomes when broadening the scope of countries under study. Twenty-eight countries on both sides of the Atlantic have collected life histories using similar instruments and health outcomes, using clinically relevant measures such as probable sarcopenia. With such comparative design emerging, findings are consolidated and knowledge is accumulated to advance efforts in delivering the UN Healthy Ageing initiative to increasingly large numbers of people throughout the world.

This chapter therefore aims to investigate the long arm thesis in many countries, which suggests that childhood conditions continue to mark old age health, and that even after youth or adult conditions are considered the partial or direct association between childhood and old age remains. To achieve this aim, a family of longitudinal ageing studies from 28 countries is used in a cross-country fixed effect design. Then to explain the mechanism behind the continuing association, this chapter also aims to investigate an epigenetic ageing hypothesis using new nationwide representative data from America: childhood poverty is associated with changes in the epigenome of individuals, especially increasing rates of methylation which turns genes on and off. With changes in the epigenome or increases in the methylation rates which control normal organ functions, such individuals have older epigenetic age for the same calendar age. Childhood conditions associate with epigenetic age even after calendar age is considered.