Lynch, John W. PhD, MPH; Kaplan, George A. PhD; Pamuk, Elsie R. PhD; Cohen, Richard D. MA; Heck, Katherine E. MPH; Balfour, Jennifer L. MPH; Yen, Irene H. PhD, MPH.  Income inequality and mortality in metropolitan areas of the United States. Am J Public Health 1998; 88: 1074-1080.

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This paper presents the first analysis of the relationship of income inequality on health at the level of cities in the US.  It used various measures of income inequality and found the strongest association of mortality with ratios of incomes of the highest nine tenth and lowest tenth of the population.  They looked at the excess mortality between the highest and lowest income inequality quarters as the disease burden attributed to income inequality.  For infant mortality, they suggest that almost 20% of the elevated death rates in high inequality cities could be from the effects of income inequality.  Similar strong affects of income inequality are found for the 15 to 34 and the 35 to 64 year age group.  Absolute income levels had a much weaker effect on mortality than did of income inequality.  An important finding was that the effect on mortality of being poor in a city with small income inequality was much less than living in a city with large income inequality.   This study showed that the magnitude of the income inequality effect on health was substantial.  The abstract below states it is equivalent to the combined loss from many major killers in the US.  It is also similar to that attributed to all deaths from heart disease in the US.  These results cry for action to reduce income inequality, if health is a goal.

Abstract

Objectives

This study examined associations between income inequality and mortality in 282 US metropolitan areas.
 Methods.  Income inequality measures were calculated from the 1990 US Census.  Mortality was calculated from National Center for Health Statistics data and modeled with weighted linear regressions of the log age-adjusted rate.
 Results.  Excess mortality between metropolitan areas with high and low income inequality ranged from 64.7 to 95.8 deaths per 100,000 depending on the inequality measure.  In age specific analyses, income inequality was most evident for infant mortality and for mortality between ages 15 and 64.

Conclusions

 Higher income inequality is associated with increased mortality at all per capita income levels.  Areas with high income inequality and low average income had excess mortality of 139.8 deaths per 100,000 compared to areas with low inequality and high  income.  The magnitude of this mortality difference is comparable to the combined loss of life from lung cancer, diabetes, motor vehicles crashes, human immunodeficiency virus (HIV) infection, suicide and homicide in 1995. Given the mortality burden associated with income inequality, public and private sector initiatives to reduce economic inequalities should be a high priority.