Issues regarding the effects on health of income inequality: contextual mechanisms

Brazil is one of the most unequal countries in income distribution. The influence of this factor on people's health is controversial. This article reviews the contextual effects and possible pathways linking income inequality to health. Contextual effect studies need well-developed multilevel theories, identifying the roles of variables in the explaining model, especially the role of individual level variables and the level of aggregation of contextual variables. Four explanations for the relationship between income inequality and health were identified: (1) statistical artifact; (2) social comparison; (3) underinvestment in social police; (4) social capital. The relative contribution of each of these mechanisms has not been well evaluated yet. We concluded that part of the heterogeneity found in the studies results may be explained by different pathways. Alternatively, income inequality may be a proxy for social stratification and less investment in public policies, but the Gini coefficient may be an unsuitable marker for such constructs in certain circumstances. More powerful designs to ascertain cause relationship should be applied. One possibility is to study the effect of intervention policies aimed at income redistribution.