The gap in life expectancy between counties has grown since 1980. In some regions, people live an average of 20 years longer than in other areas.

Americans born today in some counties can expect to live 20 years less than people in other areas of the country.

And that longevity gap has grown since 1980, according to a report published this month in JAMA Internal Medicine.

Life expectancy in 2014 was lowest in several counties in South Dakota and North Dakota — typically those with large Native American populations — and in areas in central Appalachia and the Mississippi Delta region.

“These findings demonstrate an urgent imperative, that policy changes at all levels are gravely needed to reduce inequality in the health of Americans,” Ali Mokdad, PhD, a co-author of the report, and professor at the University of Washington’s Institute for Health Metrics and Evaluation, said in a press release.

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Oglala Lakota County, South Dakota — home to the Pine Ridge Native American reservation — had the lowest life expectancy in the country at 66.8 years.

This is comparable to countries like Pakistan (66.4 years), Senegal (66.7 years), and India (68.3 years).

The study puts the average life expectancy in the United States at 79.1 years in 2014, an increase of 5.3 years since 1980.

Researchers compared death records and census returns on a county-by-county basis. The authors wrote that the overall increase in life expectancy, though, “masks massive variation at the county level.”

Some counties saw up to a 3 percent drop in life expectancy since 1980. Of the 10 counties with the greatest declines, eight are in Kentucky. The other two are in Alabama and Oklahoma.

Other counties experienced an increase in life expectancy between 1980 and 2014 of up to 18 percent. These included New York County, the District of Columbia, and four counties in Alaska.

Several of the counties with the highest life expectancy were in Colorado, with the state’s Summit County topping the list at 86.8 years — 20 years higher than the county with the lowest life expectancy.

This is even higher than top-ranking Japan, which has a life expectancy of 83.7 years.

Researchers also calculated the risk of dying for five age groups between 1980 and 2014. Risk fell in all counties for children under 5 years of age during that time. The gap between the best and worst rates in that category narrowed.

Death rates fell in most counties for the other age groups, except for 25- to 45-year-olds — 11.5 percent of counties saw an increased risk of death in this group.

The gap in the risk of death also widened since 1980 for people between 45 and 85 years of age.

The report includes a county-by-county interactive map of death rates, life expectancy, and risk factors.

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Researchers place the blame for the large gaps in life expectancy on differences in poverty, race/ethnicity, and access to quality healthcare and insurance.

Preventable risk factors like smoking, drinking, obesity, and lack of physical activity also played a big part.

Interactions among these factors are complicated.

For example, early screening for signs of cancer can increase a person’s chance of survival. But research has found that having Medicaid or no health insurance is linked to a delayed cancer diagnosis. But so is being African-American or unmarried.

“At the end of the day, socioeconomic factors are so intertwined with behavior, lifestyle, health conditions, and risk of disease that it’s almost a false dichotomy to separate them out,” said Carrie Henning-Smith, PhD, MPH, MSW, a research associate at the University of Minnesota Rural Health Research Center.

Henning-Smith also said that our society tends to place all of the blame on individuals for lifestyle choices such as eating poorly or not exercising enough.

But many things can make it difficult to be healthy, especially for people living in poverty.

People may not have easy access to healthy food or the right skills or equipment to prepare it.

Also, working multiple jobs or odd hours can keep people from being at home for the “all-important family meal.”

And unsafe neighborhoods can discourage them from exercising outside.

“All of those things can get in the way of living the ‘healthy life’ that we talk about,” said Henning-Smith.

Poverty and discrimination can also directly cause stress that leads to poorer health and an increased risk of dying.

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Researchers at the Institute for Health Metrics and Evaluation estimated that access to quality healthcare had less of an impact on life expectancy, compared with lifestyle and socioeconomic factors.

That’s doesn’t mean that health services aren’t important, just that these services play a smaller role in keeping us healthy.

“Even when we’re talking about preventive health care,” said Henning-Smith, “if people are just going to see their doctor annually or every two or three years, that’s such a blip in their lives.”

This is true even though the United States spends more than most countries on healthcare — 17 percent of its gross domestic product (GDP) in 2014, according to the World Health Organization (WHO).

In contrast, other countries with longer life expectancies spent far less, with better outcomes.

Japan spent 10 percent of its GDP, but has one of the highest life expectancies in the world. Australia spent just 9 percent of its GDP on health services, but its life expectancy is almost 83 years.

Like the United States, Australia has many immigrants and a native population. But the country has been much more aggressive in prevention — such as stricter gun control and antismoking efforts.

Other studies have also examined how the health of Americans lags behind people in other high-income countries.

“In the U.S., we’ve put altogether too much emphasis on the healthcare system,” said Henning-Smith, “and we’re not getting good outcomes for it as a whole, particularly in rural areas.”

Recent Republican attempts to replace the Affordable Care Act (ACA) may not help.

Henning-Smith said that as the House bill stands now, “we have every reason to believe that people — especially low-income people — would have diminished access to healthcare. So it may only serve to make disparities worse.”

In addition, if more people opt for watered-down “catastrophic” health insurance plans — which the Republican bill would allow — they may miss out on early screenings for cancer, heart disease, and type 2 diabetes. They may also delay treatment of these and other conditions, which can worsen outcomes.

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By itself, fixing the healthcare system may not help the country meet its Healthy People 2020 goal of eliminating health gaps and improving the health of all Americans.

“This study shows — and plenty of other studies have shown — that if we really want to reduce health disparities, if we really want to increase life expectancy, we need to move outside of healthcare,” said Henning-Smith.

Mokdad suggested that “federal, state, and local health departments need to invest in programs that work and engage their communities in disease prevention and health promotion.”

Public health efforts have already made great strides in these areas, such as reducing cancer deaths through anti-tobacco and early cancer screening programs.

For these to reach every American, though, they may need to dig a little deeper.

“We really need to move upstream and start thinking about how to address the root cause,” said Henning-Smith. “And the root cause in a lot of cases is poverty and income inequality.”