However, Dr. Benjamin Honigman of the University of Colorado School of Medicine and director of the Altitude Medicine Clinic and colleagues also found altitudes above 4,900 feet were detrimental to those suffering from chronic obstructive pulmonary disease.
"If living in a lower oxygen environment such as in our Colorado mountains helps reduce the risk of dying from heart disease it could help us develop new clinical treatments for those conditions," Honigman said in a statement.
"Lower oxygen levels turn on certain genes and we think those genes may change the way heart muscles function. They may also produce new blood vessels that create new highways for blood flow into the heart."
The research team spent four years analyzing death certificates from every county in the United States for cause of death, socioeconomic factors and other data.
The study, published in the Journal of Epidemiology and Community Health, found of the top 20 counties with the highest life expectancy -- 75.8 to 78.2 years for men 80.5 to 82.5 years for women -- 11 for men and five for women were in Colorado and Utah with a mean elevation of 5,967 feet above sea level.