The widening divide between rich and poor is impacting more than the bank accounts of the have and have-nots. It's also putting measurable stress on Americans' health.

Residents of communities with high levels of income inequality are more likely to suffer from negative health outcomes than those who live in more equal counties, according to recent research from County Health Rankings & Roadmaps program, a collaboration between the University of Wisconsin Population Health Institute and the Robert Wood Johnson Foundation.

While income itself has a bigger influence on health, since poverty impacts everything from nutrition to access to medical care, researchers found that income inequality adds another level of stress to a community. People living in unequal counties, for instance, were more likely to die before they reached 75 than people living in communities with more equal incomes, even after controlling for household income, the study found.

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"There was compelling evidence that not only being poor is harmful, but living in a community with big gaps between the poor and the more wealthy could add stress to the lives of poorer people, and people living in poor but high inequality areas end up with higher risks" for issues such as cardiovascular disease, said Bridget Catlin, co-director of the County Health Rankings & Roadmaps program.

The group studies county-level data to determine what policy and environmental factors at the community level can impact health, rather than at the larger state or federal level. Finding that income inequality at the county level is impacting health was surprising, Catlin said. The good news is that the research suggests communities can make real changes at smaller levels that will improve residents' health, such as if private companies offer paid sick leave, which would help reduce poverty, or private and public investment in education and workforce development, she noted.

Counties with the highest inequality tend to be clustered in a few regions of the country: the South, the Southwest, the northern Plains states, and Appalachia. The researchers developed a measure of inequality by comparing the ratio of household income at the 80th percentile to that of the 20th percentile in each U.S. county.

Take Westchester County in New York State. While the country's ratio for income inequality stands at 4.4, it's much higher in Westchester, at 5.8. A popular community for New York financial executives, it's known for expensive housing and high incomes. About one-quarter of its households earn more than $150,000 annually. The flip side is that many households are living in the shadow of that wealth, with about one in seven households living on less than $25,000 in annual income.

Because so many of its residents are wealthy, the county throws off the "false perception of ubiquitous affluence," while its poorer residents struggle and often feel invisible, according to the local advocacy group the Empire State Economic Security Campaign of Westchester.

Counties with high rates of income inequality suffer because it fosters a loss of social connections, Catlin noted.

She noted, "Communities where people are more similar feel more connected and feel more of a sense of community than where there are" groups with large socio-economic gaps, she noted. "Whenever you lose social connections, you end up with less trust and social support."