Recent search shows that even on a county by county basis, greater income inequality negatively impacts overall health. A study from Population Health Institute at the University of Wisconsin provides evidence that living in a more unequal U.S. county is associated with lower levels of health as measured by likelihood of dying before age 75. We all know that living in a poor community is associated with worse health but this study shows that inequality has an impact independent of overall level of income. Two counties with the same average income will show health affected by different levels of income inequality. You can read more in an article in the NY Times at http://www.nytimes.com/2015/03/31/upshot/income-inequality-its-also-bad-for-your-health.html?abt=0002&abg=1
This relationship has been well researched and is generally accepted by epidemiologists and health sociologists. What is not yet well understood are the pathways by which income inequality impacts life expectancy. The article reviews the major speculations and the research underway to better understand. But it is clear that a more equal society in terms of income is better for everyone in the society.