Life expectancies for men and women in Los Angeles County rose in the last two decades.
Los Angeles County has among the highest life expectancies in the country despite a poverty rate above the national average. Countywide, women live more than a year longer than they do nationally, and men live more than eight months longer on average.
This may be evidence of what demographers and public health officials call the "Hispanic paradox," a long recognized phenomenon in which Latino immigrants are generally healthier than non-Latinos of similar income.
Nearly half of Los Angeles County's 10 million residents are Latino, and more than a third are foreign born, according to census data. By contrast, less than a sixth of the population nationally is Latino, and less than an eighth is foreign born.
One explanation of that phenomenon is that the people who become immigrants tend to be healthy. "These are not random people. They are the healthiest people who could get here," said Carmen Nevarez, former president of the American Public Health Assn.
But David Hayes-Bautista, who heads the Center for the Study of Latino Health and Culture at UCLA, said other factors, including social support networks, diet and even physical labor, may play a role as well, because not all immigrants have such good health outcomes as Latinos.
Some rural parts of the nation also have done well, with areas of Minnesota, Wisconsin and Iowa having some of the highest life expectancies.
"These are not wealthy communities," Murray said, noting that many benefit from a "cohesive community" that may improve health outcomes.
Murray and other researchers noted that the data also suggest that communities can improve their health outcomes with sustained public health initiatives.
New York City, for example, which has pursued aggressive anti-smoking and anti-obesity campaigns, has among the higher life expectancies in the nation.
Murray and his team also found very high life expectancies among a group of counties in the Mountain West such as Gunnison County, Colo., and Teton County, Wyo., that have become lifestyle destinations.
The changing demographic profile of these counties only explains part of that achievement, Murray said. "They can actually change the environment and the community's values," he said.