Lynch J, Kaplan GA. Understanding how inequality in the distribution of income affects health. Journal of Health Psychology 1997; 2: 297-314

This important, provoking review begins with Plato who felt that the maximum extremes of wealth in society should not be higher than four fold. [Today, it is likely that the extremes are at least a quadrillion (thousand million million) fold.] It makes the important conceptual point that most studies have focussed on individual risk factors, rather than looking at a population as an organism, with its risk factors for poor health. Income inequality appears to be the strong factor associated with a population's health, be it a country, or a local region within a country. The few existing criticisms of this approach are discussed and it is pointed out that there is little dissension from the strong support presented for the association.

Two intertwining strands exist for understanding how the inequitable income distribution might impact health:

1. inequitable income distribution may be associated with set of social processes and policies that systematically underinvest in human, physical, health and social infrastructure, and this underinvestment may have health consequences

2. inequitable income distribution may have direct consequences on people's perception of their social environment that influence their health

Finally, the article outlines directions future epidemiologic studies might take to further clarify this relationship. 

Abstract

Research on the determinants of health has almost exclusively focused on the individual but it seems clear we cannot understand or improve patterns of population health without engaging structural determinants at the societal level. This article traces the development of research on income distribution and health to the most recent epidemiologic studies from the USA that show how income inequality is related to age-adjusted mortality within the 50 states. (r = -0.62, p = 0.0001) even after accounting for absolute levels of income. We discuss potential material, psychological, social and behavioral pathways through which income distribution might be linked to health status. Distributional aspects of the economy are important determinants of health and may well provide one of the most pertinent indicators of overall social well-being.

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