The field of life course epidemiology has expanded rapidly since this book was first published. The purpose of this field is to study how biological and social factors during gestation, childhood, adolescence, and earlier adult life independently, cumulatively, and interactively influence later life health and disease. Contributors to this edition capture the excitement of the developing field and assess the latest evidence regarding sources of risk to health across the life course and across generations.

The present discussion paper sets forward a model within the life course perspective of how the social becomes biological. The model is intended to provide a framework for thinking about such questions as how does social class get into the molecules, cells and tissues of the body to produce social class differences in life expectancy and cause of death? A categorisation of social exposures and biological processes is suggested; and some principles governing their inter-relations proposed. The paper ends by suggesting two public health applications of this approach.