Way up high in Colorado, where tourists get nauseous, the locals live and keep on living – longer than virtually any other place in the United States. A new Harvard University longevity study puts seven high-country Colorado counties in the top 10 in the nation, with an average lifespan of 81.3 years.

"I don’t let the grass grow under my feet," said Shirley Willis, 83, of Dillon, one of those Rocky Mountain octogenerians. "I’m busy, and I’m interested in what’s going on in my community. We have good air and pure, clean water."

Melvin Long, 81, has been running his ranch in Summit County for 50 years. Regarding the long lives of his neighbors, Long suggested that maybe it’s their work ethic.

"When my mother changed my last diaper, she told me, ‘Go find a job,’ " he said.

The study, "Eight Americas: Investigating Mortality Disparities Across Races, Counties and Race- Counties in the United States," was done by the Harvard School of Public Health with funding from the Centers for Disease Control and Prevention and the Institute on Aging.

Appearing in today’s issue of Public Library of Science Medicine, the study found great disparities in average lifespan by county, race and income but fell short of being able to explain why.

The Colorado counties sharing the top spot for average life expectancy were Summit, Park, Eagle, Clear Creek, Gilpin, Jackson and Grand.

Tied for 24th place among the thousands of counties in the U.S. were six other high-country counties in the state: Archuleta, Mineral, Ouray, San Miguel, Gunnison and Hinsdale, with an average longevity of 80.8 years.

Douglas and Elbert counties, closer to the Front Range, tied for 49th at 80.3 years.

Colorado was in the second tier in statewide longevity, with California, Connecticut, Massachusetts, Minnesota, North Dakota, New Hampshire, Vermont and Washington, all with life expectancies topping 78 years. Only Hawaii’s 80 ranked ahead of that group.

The District of Columbia ranked lowest, with a life expectancy of 72 years. Four Southern states, Mississippi, Louisiana, Alabama and South Carolina, had life expectancies of less than 75 years.

But it’s the great disparity in county rankings that caught the authors’ attention.

The six counties with the lowest lifespan – 66.6 years – were in areas of South Dakota where the American Indian population is high. Among American Indians living in South Dakota, life expectancy is just 58 years.

It was such findings that led the authors to carve out eight separate Americas, when it comes to longevity.

On the high end are Asian-Americans, who live almost six years longer, on average, than other Americans.

On the low end are American Indians, rural whites in the South and rural and inner-city blacks.

The longevity gap within the eight Americas is comparable to the gap between Western European countries and some developing countries.

There is a 15-year gap in life expectancy between men in Iceland and men in Belarus, for example. That same 15-year gap exists between Asian-American males and high-risk urban blacks.

Most of Colorado is in the huge group of 214 million "middle" or mainstream Americans, which includes most of the nation’s whites and Asians. The study didn’t delineate Hispanic lifespans.

Among that large group, men live to an average age of 75 – which is three years better than 20 years ago. Women live to an average age of 80 – one year better than 20 years ago.

Dr. Ned Calonge, Colorado’s chief medical officer, said he doesn’t think there’s anything magic in the high-country air.

Instead, he points to Colorado’s relatively low smoking rate, its lowest-in-the-nation obesity rate and to the active lifestyle. But that’s about as far as he would go in saying what may account for the state’s ranking.

Colorado’s high-country residents have long noted that their neighbors tend to move to Grand Junction, Florida or Arizona when they grow old to escape the cold winters or because the thin air is tough on their lungs and heart.

Calonge himself notes that where people die isn’t necessarily where they have lived most of their lives.

There’s nothing different about mountain living, from a health perspective, that makes it better than other parts of Colorado, he said.

It could be simply that retired people who choose to move to the mountains may be a hardier group than those who choose to move to Florida or Arizona.

But Tom Long, a Summit County commissioner, said high-country residents seem to have a certain robustness.

"There is an attitude up here, a lifestyle, of people staying in shape by hiking, hunting, fishing or biking," he said.

Long’s dad, Melvin, for example, still ranches despite asthma, which requires him to breathe bottled oxygen while he sleeps.

Shirley Willis hikes, plays golf and does political work.

"It’s a healthy place," she said of Summit County. "And there’s a lot for seniors to do."