A LIFECOURSE APPROACH TO HEALTH and exposures at different life stages accumulate and create the social inequalities in morbidity and mortality observed in middle and old age(Davey Smith, 2000; Leon, 2000) A life course approach to adult health is not a new concept-the idea that experiences in earlier life hape adult health, was the prevailing model of public health in the first half of the twentieth century In the post war period the dominance of the adult life style model for adult chronic disease was due to the early success of cohort studies in confirming, for example, smoking as a major risk factor for lung cancer, coronary heart disease and respiratory disease, and hypertension as important for stroke and IHD. However, conventional risk factors are limited in predicting individual risk and only partially explain the striking social and geographical inequalities in the distribution of chronic disease. Since the 1980s, there has been a revival of interest in life course epidemiology in response to growing empirical evidence from the maturing birth cohort studies and the revitalisation of historical cohorts Conceptual models of the life course The simplest classification groups conceptual models of the life course under 4 headings 1 A critical period model 2 A critical period model with later effect modifiers 3 Accumulation of risk with independent and uncorrelated insults 4 Accumulation of risk with correlated insults(clustering, chains or pathways of risk) There is evidence for all four models. A critical period model is when an insult during a specific period of development has lasting or lifelong effects on the structure or function of organs, tissues and body systems. Evidence suggests that later life factors may modify this early risk(model 2) For example, studies have shown that the relationships of coronary heart disease, high blood pressure and insulin resistance with low birth weight are particularly strong for those who are overweight(see figure)(Frankel et al, 1996; Lithell et al 1996; Leon et al, 1996) In contrast, the gradual accumulation of risk models encourage researchers to study how risk factors at each life stage combine to raise disease risk. Do separate and independent insults gradually cause long-term damage to health(model 3)? Risk factors tend to cluster in socially patterned ways, for example, those living in adverse childhood social circumstances are more likely to be of low birth weight, and be exposed to poor diet, childhood infections and passive smoking. These exposures may raise the risk of adult respiratory disease, perhaps through chains of risk or pathways over time where one adverse(or protective) experience will tend to lead to another adverse(protective) experience in a cumulative way(model 4). As well as the biological chains of risk linked with programming, there are social chains of risk where, for PAGEFIVEA LIFECOURSE APPROACH TO HEALTH PAGEFIVE and exposures at different life stages accumulate and create the social inequalities in morbidity and mortality observed in middle and old age (Davey Smith, 2000; Leon, 2000). A life course approach to adult health is not a new concept – the idea that experiences in earlier life shape adult health, was the prevailing model of public health in the first half of the twentieth century. In the post war period the dominance of the adult life style model for adult chronic disease was due to the early success of cohort studies in confirming, for example, smoking as a major risk factor for lung cancer, coronary heart disease and respiratory disease, and hypertension as important for stroke and IHD. However, conventional risk factors are limited in predicting individual risk and only partially explain the striking social and geographical inequalities in the distribution of chronic disease. Since the 1980s, there has been a revival of interest in life course epidemiology in response to growing empirical evidence from the maturing birth cohort studies and the revitalisation of historical cohorts. Conceptual models of the life course The simplest classification groups conceptual models of the life course under 4 headings: 1 A critical period model 2 A critical period model with later effect modifiers 3 Accumulation of risk with independent and uncorrelated insults 4 Accumulation of risk with correlated insults (clustering, chains or pathways of risk) There is evidence for all four models. A critical period model is when an insult during a specific period of development has lasting or lifelong effects on the structure or function of organs, tissues and body systems. Evidence suggests that later life factors may modify this early risk (model 2). For example, studies have shown that the relationships of coronary heart disease, high blood pressure and insulin resistance with low birth weight are particularly strong for those who are overweight (see figure) (Frankel et al, 1996; Lithell et al 1996; Leon et al, 1996). In contrast, the gradual accumulation of risk models encourage researchers to study how risk factors at each life stage combine to raise disease risk. Do separate and independent insults gradually cause long-term damage to health (model 3)? Risk factors tend to cluster in socially patterned ways, for example, those living in adverse childhood social circumstances are more likely to be of low birth weight, and be exposed to poor diet, childhood infections and passive smoking. These exposures may raise the risk of adult respiratory disease, perhaps through chains of risk or pathways over time where one adverse (or protective) experience will tend to lead to another adverse (protective) experience in a cumulative way (model 4). As well as the biological chains of risk linked with programming, there are social chains of risk where, for