Income inequality and mortality: importance to health of individual income, psychosocial environment, or material conditions

British Medical Journal, April 29, 2000 by John W Lynch, George Davey Smith, George A Kaplan, James S. House

A metaphor

To appreciate how neo-material conditions can influence health, it may be useful to consider the metaphor of airline travel. Differences in neo-material conditions between first and economy class may produce health inequalities after a long flight. First class passengers get, among other advantages such as better food and service, more space and a wider, more comfortable seat that reclines into a bed. First class passengers arrive refreshed and rested, while many in economy arrive feeling a bit rough. Under a psychosocial interpretation, these health inequalities are due to negative emotions engendered by perceptions of relative disadvantage. Under a neo-material interpretation, people in economy have worse health because they sat in a cramped space and an uncomfortable seat, and they were not able to sleep. The fact that they can see the bigger seats as they walk off the plane is not the cause of their poorer health. Under a psychosocial interpretation, these health inequalities would be reduced by abolishing first class, or perhaps by mass psychotherapy to alter perceptions of relative disadvantage. From the neo-material viewpoint, health inequalities can be reduced by upgrading conditions in economy class. Of course, this simplistic metaphor assumes that conditions in first class and economy class are independent--in the real world, improvements in economy are often resisted by those able to travel first class.

Examples from India and Britain

Cross nationally, higher levels of social expenditures--markers of neo-material conditions--are associated with greater life expectancy, lower maternal mortality, and a smaller proportion of low birthweight babies.[42] Thus, strategic social investment may be important in determining health differences between countries. Interpretation of health differences between and within countries should be based on a historical view of social conditions and policies. Consider, for example, the widely discussed favourable health situation in Kerala state, India.[43] Despite low individual income the infant mortality, maternal mortality, childhood mortality, and overall mortality in Kerala are better than in other Indian states and approach levels in richer, industrialised countries. Greater redistributive actions of the Kerala government over recent decades have been viewed as the phenomenon underlying this. It is also the case, however, that the social and cultural basis for these favourable health outcomes can be traced to over a century of social activities that have promoted greater gender equality, education, and general public investment in human resources.[44]

In Britain, income inequality increased greatly from the mid-1970s to the 1990s, but mortality in middle age and at older ages declined dramatically. Correlations between income inequality and mortality range from r=-0.76 for men aged 55-64 to r=-0.86 for women aged 45-54 (fig 3). Understanding the rapid decline in mortality in middle age against a background of escalating income inequality in Britain may require consideration of earlier social investments. Expansion of the welfare state, educational opportunities, and introduction of the NHS had positive influences in early life for those cohorts in which mortality is currently declining, and social circumstances in early life can have important long term effects on later risk of death.[45 46] Such findings encourage a view that health in adulthood is the outcome of socially patterned processes acting across the entire life course.[47] This perspective would lead to attention being paid to how income inequality--and the broader social processes which income inequality indexes--influences health across the life course of successive cohorts. In several countries, the burden of increased income inequality has fallen disproportionately on poor households containing young children, and this may lead to poor health outcomes in the future.[45-48]