A graded association of lower socioeconomic status (SES) with increased incidence of diabetes and coronary heart disease has been shown repeatedly (1
). These associations are often interpreted to indicate that SES affects health, either directly or indirectly (the social causation hypothesis). Low SES is associated with low income, poor career prospects, and greater risk of unemployment. All of these factors determine the ability to consume goods and services—for example, high-quality food or health care—which in turn affects health (8
). Income differences, even if income is above the poverty line, may also lead to differential access to social participation and social capital, which are related to health inequalities (10
). Low SES is also associated with higher exposure to occupational health hazards, both physical and psychosocial, potentially contributing to health problems (14
). Furthermore, differences in social values and behavioral preferences between SES groups may create variations in health (19
The relation between SES and health is not necessarily unidirectional, since health can function as a selective mechanism in relation to SES (20
). It has been suggested that childhood health is linked to educational achievement and labor market prospects and thus to adult SES, which might account for the socioeconomic differences in health in adulthood (the health selection hypothesis) (22
). Particularly severe and limiting health problems during adulthood may increase the risk of an income shortfall and poor career prospects. Although the strength of these associations is likely to be dependent on the health problem in question and the local social policy context, it has been argued that persons with severe chronic illness tend to be poorer because their illness endangers their economic potential and resources (26
Taken together, this evidence is consistent with the hypothesis that the relation between SES and health is reciprocal, bound in a reinforcing cycle where the direction of causality is difficult to determine (27
). It is possible, for example, that although both health selection and social causation operate over the life course, their relative importance varies from one developmental stage to another. Health problems early in life may have severe and long-term consequences, as they affect educational attainment and subsequent adult SES (22
). In contrast, health problems that emerge in adulthood may play only a minor role in the overall relation between health and change in SES (11
). Longitudinal research designs are needed to capture such life-stage-dependent relations. Furthermore, research using objective indicators of health would strengthen the existing evidence, since self-report measures may be biased by socially patterned reporting of health.
In this study from the Whitehall II cohort (2
), we investigated health-related selection and social causation using repeated measurements of objectively assessed cardiometabolic factors in adulthood. To assess the selection process at different stages of the life course, we examined the extent to which childhood health predicted socioeconomic mobility and the extent to which adult cardiometabolic factors, such as obesity, high blood pressure, lipid levels, glycemia, and inflammation, predicted future promotion at work. To study social causation, we assessed whether adult SES predicted change in cardiometabolic factors over a 10-year period.