Health inequalities and social inequalities in health.

In vol. 77, issue no. 7 of the Bulletin, published in july 1999, Murray, Gakidou, & Frenk (1) recommend assessing "health inequalities" by categorizing individuals only according to their health, without reference to other characteristics except perhaps geographical location. They repeat this recommendation in vol. 78, issue no. 1, published in January 2000 (2). In both articles, they contrast studying what they term "health inequalities across individuals" with studies of social inequalities in health, which examine the health of different population groups categorized a priori by their social position, typically reflected by measures of social class or material or social deprivation or well-being. In the first of these articles they advance the serious claims that studying social inequalities in health inherently prejudges causality, masks intra-group variation, and "does not allow for scientific inquiry into other key determinants of health inequality"(1). It is unfortunate that Murray et al. felt a need to discredit research on social inequalities in health in order to recommend their approach; the two approaches are not only not mutually exclusive, but ask very different questions. We believe their argument is based on misconceptions, as illustrated by the recommendation to compare health inequalities across geographical regions but not social groups. Geographical comparisons are similar to social group comparisons in that both involve a priori selection of a categorizing variable based on knowledge indicating its likely relevance. Furthermore, differences between geographical areas are likely to reflect social characteristics to an important extent, and studying geographical variation in relation to socioeconomic and other social conditions can provide important insights into population distributions of health (3-6). By suggesting that their approach to "health inequalities", rather than what they term the "social group" approach, ought to guide public health policy, Murray et al. create a situation in which their claims could be used (despite good intentions) to prevent social inequalities in health from occupying an important place on the global research and policy agenda. We also are concerned about the implications of the ethical perspective propounded in the article in vol. 77 for setting public health priorities. Studying social inequalities in health does not mean prejudging causality or obscuring intra-group variation, any more than comparing health between geographical areas prejudges causality or prevents studying variations within the areas. Observing mortality gaps according to educational level obviously cannot be interpreted to mean that education per se is the cause; however, it points one in a promising direction by prompting questions such as: Why is educational level persistently associated with diverse health measures across time and diverse settings? How do people with different levels of educational attainment differ from each other in ways that could potentially explain the observed mortality disparities? And: Among people with low education, what might account for differential risks of mortality? In contrast, the univariate approach that Murray et al. propose, examining the distribution of health without considering other population characteristics, leaves one, after the initial descriptive step, only with the general question: What factors differ between individuals with better or worse health? This does not suggest even a general direction to look towards for an explanation of those inequalities. Comparing groups with each other imposes neither conceptual nor methodological limitations on examining variation within those groups; we do not understand why Murray et al. imply that these are mutually exclusive. We also are unclear as to why Murray et al. deem the "social group" approach a hindrance to the scientific study of population health. The basis for using certain social factors as categorizing variables is the overwhelming evidence of their importance as health determinants, across diverse health outcomes, settings, and time periods (7-20). …