You are a "holy nation” the author of First Peter says this Sunday to members of the early church in Asia Minor. When it comes to being a “healthy nation,” however, much depends on where you happen to live. In fact, life expectancy at birth in the United States differs by as much as 20 years between the lowest and highest counties, according to new research published in the medical journal JAMA Internal Medicine.

Dr. Christopher J.L. Murray, lead author of the study and director of the Institute for Health Metrics and Evaluation at the University of Washington, estimated life expectancy for each U.S. county from 1980 through 2014. Murray and his colleagues analyzed county-level data and then applied a mathematical model to estimate the average length of lives.

While the study does not directly answer why we see low or high life expectancies in specific counties, it does look at what factors contribute to the overall gap between some counties, said Murray.

“We can see that many of the counties with very low life expectancies in the Dakotas, like Oglala Lakota County in South Dakota, overlap with large Native American reservations including the Pine Ridge and Rosebud reservations,” said Murray. Conversely, Summit County, Colorado, ranked as the county with highest life expectancy in 2014 at 86.8 years, is home to several ski resort towns.

“For both of these geographies, the drastically different life expectancies are likely the result of a combination of risk factors, socioeconomics, and access and quality of health care in those areas,” said Murray.

Yet, socioeconomic factors are not everything, said Murray, explaining that “60 percent of the differences in life expectancy across counties can be explained by socioeconomic factors alone” yet that leaves a “substantial amount of unexplained differences.”

“Behaviors like smoking and physical activity, along with risk factors like obesity and diabetes, are also very important,” he said.

Although geographic differences in mortality rates decreased over time for children and adolescents, they rose for adults—especially those between the ages of 65 and 85. That makes senior citizens “an especially important target for future research and intervention,” the study authors wrote.

“Tracking inequality at the county level over time is an important means of assessing progress toward the goal of more equitable health outcomes,” the study authors wrote.

Lessons drawn from the readings

In the gospel reading this Sunday, Jesus reminds his followers that he is the way, the truth, and the life. When charting the way forward for public health, officials can use the U.S. Health Map to guide and focus their efforts to do the most good. 

Final thought in light of the news

For the richest nation on the earth to have such disparities in life expectancy is truly disturbing. Researcher Ellen Meara, who studies health policy at the Dartmouth Institute, speculates that the findings could be another manifestation of the economic inequality plaguing areas of the country. The discrepancy is equivalent to the difference between the low-income parts of the developing world and countries with high incomes. For example, it’s about the same gap as the difference between people living in Japan, which is among countries with the longest life spans, and India, which has one of the shortest. The stark reality is that within the richest nation on earth hides one of the poorest. This should be morally unacceptable to one and all. Let’s do better, together.