Commentary: Social inequalities in health, social epidemiology and social value

The collection of eight papers presented in this volume add to the impressive social epidemiology literature on inequalities in health. In these latest contributions a variety of data sets from a range of countries are analysed using rigorous epidemiological methods. In each case, those in poorer social circumstances fare less well than those with better social circumstances, whether one is concerned with outcomes such as overall or cause-specific mortality, or health risk factors such as cognitive function or behavioural threats to health. These inequalities remain after controlling for known risk factors such as smoking behaviour. Even among heavy smokers, those in better social circumstances seem to be in some way ‘protected’ against some of the consequences experienced by heavy smokers in poorer social circumstances. Other studies have shown that social inequalities extend further to the association between known risk factors and health,1,2 the uptake of interventions aimed at reducing risk factors or improving health3,4 and the outcome of interventions.5,6 Despite the pervasiveness of social inequalities at each stage of the production of health, illness and recovery in populations, the literature remains largely confined to the identification and description of the problem of social inequalities and provides little insight into solutions to the problem. In common with other contributions, many of the papers in the current collection conclude with calls for reductions in social inequalities in health risks and effective public policy, targeted at less prosperous groups to achieve these reductions in inequalities. However no direction is offered concerning what these interventions might be or how we might go about uncovering such interventions. The ‘black box’ of how to reduce social inequalities in health remains relatively unexplored by social epidemiologists. But whose interests are served by further information that the poor come off worst in many aspects of the production of health, illness and recovery in populations? What is the social value, as opposed to the scientific merit, of more ‘replications’ of the social inequalities research? How can the achievements of social epidemiological research to date be used to contribute to identifying ways of reducing social inequalities in health? The literature on social inequalities in health has been instrumental in leading to the development of broad conceptual frameworks for thinking about health in a population context.7,8 However, these frameworks are both incomplete and underutilized in the discussions about addressing social inequalities in health. Although the frameworks emphasize the range of factors that contribute to health (the determinants of health), they are largely unhelpful in understanding the distribution of these determinants within populations due to a lack of social theory within the frameworks.9 For example, the importance of behavioural factors such as smoking in the production of health and the impact of social variations in smoking patterns on the distribution of health are accommodated within the frameworks. However, Marmot and Theorell10 have argued that the identification of social patterning in risk factors is insufficient and that the question needs to be asked, why are risk factors social class based? Despite this limitation, the frameworks are helpful in emphasizing the complex ways the range of health determinants ‘operate’ in the production of health, illness and recovery in populations. But, application of the frameworks in research studies and policy discussions has often ignored these complexities in favour of simple research questions based on individual elements of the broader framework. The underlying assumption is that elements of the complex system of health production can be studied in isolation of the other parts of the system and that the results produced by these more focused enquiries represent ‘truths’ that are free of influence from other elements of the system.11 However this involves a shift in focus of attention and leads to the research questions pursued and research methodologies used being of limited relevance to the realities uncovered in social epidemiological research. While the principles of epidemiology may be retained in the search for solutions, the social setting for the research is set aside in order to satisfy economic imperatives to maximize the productivity of scarce resources devoted to programmes and to the research required to study those programmes. The problem is transformed from one concerning the distribution of health between all social groups in a population to one of the effectiveness of interventions in particular groups in the population.12 The chain of thinking seems to be ‘if poorer groups suffer disproportionately in terms of mortality or morbidity from condition X, and we can find an effective treatment for condition X, then we can reduce social inequalities in health pertaining to condition X by making it available to anyone with condition X’. A major implication of this further shift in focus is that a condition (e.g. lung cancer), or particular risk factors associated with a condition (e.g. smoking), becomes the central theme of interest, not the social settings in which the condition is experienced. Individuals with the condition or risk factor form the population of interest and are viewed as a homogeneous problem group. Population heterogeneity in terms of the distribution of the condition or risk factor associated with the condition, so important to social epidemiology, is a nuisance to researchers trying to estimate the effectiveness of programmes for condition X. A sample of individuals is selected from those with the condition. Population heterogeneity within this sample is ‘cleansed’ by random selection of individuals in the sample to receive the programme, precisely because of the possibility that the individuals with the same condition might not be identical in terms of factors relevant to the effectiveness of the intervention. Randomization maximizes the probability that the distribution of factors that social epidemiology has uncovered as important in the production of health illness and recovery in populations is the same in the groups receiving the programme under study and those who do not receive it. The characteristics that made people different (and interesting) in social epidemiology are factors that make people difficult (and ‘noisy’) in health services research! The studies generate information about whether the intervention ‘works’ on average in the sample chosen but fails to provide information about the types of people for whom the intervention works best, or whether the intervention works at all for particular groups (e.g. those for whom the burden of the condition is greatest). Failure to take account of heterogeneity in the study sample can lead to ‘effectiveness reversal’ in which the results of well-conducted trials indicate that the benefits of intervention A exceed the benefits of intervention B in a study population although for all subgroups of the population (e.g. rich and poor) the benefits of B exceed the benefits of A.13 The ‘evidence’ provided by the trials' data is simply an artefact of the distribution of the social determinants of health in the study population (or what Utts14 describes as a variation of Simpson'o;s Paradox).15 More likely, the improvements in health associated with a particular programme may be conditional upon or related to other characteristics of the groups of the population with the condition.5,6 For example, the prevalence of smoking is greatest in poorer groups of the population, but smoking cessation schemes have been found to be more effective in better-off groups of smokers. Where the intervention includes increased taxation on cigarettes as a source of programme funding, the burden of funding is increasingly concentrated on those who fail to quit, generally poorer groups. In this way the poor pay for the health benefits of the rich. Evidence of the absence of the social nature of health inequalities in policy discussions on social inequalities in health is provided by the recent report of the UK enquiry into inequalities in health.16 For example: In the model of determinants of health used to guide the enquiry, relationships between particular health determinants and health outcomes are considered in isolation of the prevailing levels of other health determinants. For example, although the model implies that social conditions might influence an individual's probability of smoking, the impact of smoking on health is independent of these social conditions. The report recognised the existence of social gradients in health in which health is related to social position not merely social deprivation. However many of the recommendations of the report focused on matters associated with material conditions of the least well off. Recommendations were made concerning minimum wage legislation, increasing employment opportunities and income supplements for the non employed, all aimed at populations at high risk of poverty, with little attention being given to the population redistribution of income, wealth and opportunities more generally. The poverty-health relationship is one small part of the complex system of production of health in populations. Recommendations based on this one element in isolation of the complex system of health production could, under some circumstances, be harmful to the health of those they are intended to help, thus increasing the health divide between the ‘haves’ and ‘have nots’. A series of recommendations concerning nutrition, exercise and smoking were made based on careful evaluation of these programmes. However, in some of these studies health was not measured as an outcome while in others, the measurement of health outcomes was limited to non-poor populations. Over 15 years ago Syme17 commented on the tendency for research designs to abstract from social reality noting that: “Everyone is aware of the fact that patterned irregularities in disease rates exist for socioeconomic status, race, sex, marital status, religious groups, geographic areas and so on…most epidemiology research ‘holds constant’ these ‘background’ factors so that more interesting variables can be studied. This is done because it is tacitly recognised that if the factors were not statistically removed from the analysis they are so powerful that they would overwhelm everything else being studied. In consequence these factors are rarely studied in their own right.” Social epidemiologists have embraced this message as witnessed by the expansion of literature on social inequalities in health. However there is little evidence that the message has reached the other disciplines involved in health research. Considerable interest has been expressed in how inequalities in various social, economic and psychosocial factors in populations affect health, but research has largely focused on the average health in the population as an outcome, not the distribution of health underlying the average.18 Failure to incorporate the richness of social epidemiological research in the development and application of conceptual frameworks has been associated with a dismal track record of governments with respect to reducing social inequalities in health irrespective of varying commitments to ‘health for all’ and social justice. Little if any evidence is available on policies, progammes or interventions that are effective in reducing social inequalities in health.19 Faced with this vacuum of information, policy makers have tended to adopt a ‘second best’ approach by shifting attention away from the population distribution of health, health inequalities, to the health of the poorest groups in society, health poverty, and to conditions that the poor tend to suffer from in isolation of the circumstances in which those conditions are suffered. Meanwhile health inequalities have persisted and, in many cases, increased. Social epidemiology has shown us that adverse social, economic and physical environments inhibit the production of health in populations. It would therefore seem important that these same social, economic and physical environments be included as part of research studies aimed at identifying solutions to inequalities in health and health poverty. The social distribution of the burden of the condition in the population should at least be reflected in the sample to be studied. Yet inability to communicate in the English language and social factors inhibiting a person's compliance with study protocols are often adopted as criteria for excluding population groups from studies as a way of easing the burden for researchers. Given the ‘gold-standard’ nature of randomization among health services researchers why is there reluctance to consider random selections of the population of interest? Representativeness in the study sample alone is unlikely to be the panacea for social inequalities in health, because interventions chosen for study tend to ignore the social context in which risks occur and illness is experienced. As a result, programmes that researchers identify as effective on average in study populations might be wasteful when provided to poorer groups because they represent middle class solutions to what are predominately working class problems. Significant contributions to understanding the nature of health problems and identifying effective solutions to those problems have been made by studying the problems in the context in which they occur.20,21 Expanding the ‘scope of practice’ to incorporate health policy and health services research provides an opportunity for social epidemiologists to add social value to the scientific merit of their work. There is probably no group of academic researchers in a better position to provide this leadership.

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