Two trends stand out in new projections of life expectancy in developed countries released Tuesday by the Lancet:

The United States, with large income inequalities and a host of other social issues that affect health, is falling farther behind most other wealthy nations. From 2010 to 2030 it will experience among the smallest increases in life expectancy for women (up 2.1 years to age 83.3) and men (up 3 years to age 79.5). Both are the fourth-smallest increases among the 35 nations studied.

South Korea, which has systematically worked to improve living conditions across social classes, according to the researchers, is poised to reach 90.8 years average life expectancy for females by 2030, both the highest in the developed world and the biggest jump from 2010. Male life expectancy (84.1) would be the highest as well.

Next-highest in 2030 for women is France (88.6) and Japan (88.4); for men it is  Australia and Switzerland (both 84).

Life expectancy is projected to increase in all 35 countries but at vastly different rates, according to the researchers, who said they developed and combined 21 models to make the projections, using a statistical technique that is common in weather forecasting.

The expected gains in South Korea are likely due to broad-based improvements in residents' financial status, education, nutrition, and access to both primary care and new medical technologies, the researchers wrote.

By contrast, countries with the smallest increases in life expectancy tended to have the most  social inequality, with the worst-off groups pulling down the average. Previous studies using different methods, for example, have found life expectancy in Philadelphia lags several years behind the surrounding suburban counties.

"Notable among poor-performing countries is the USA, whose life expectancy at birth is already lower than most other high-income countries, and is projected to fall further behind such that its 2030 life expectancy at birth might be similar to the Czech Republic for men, and Croatia and Mexico for women," the international team of  researchers wrote. "The USA has the highest child and maternal mortality, homicide rate, and body-mass index of any high-income country."

It is also the only country in the Organization for Economic Cooperation and Development, they wrote, "without universal health coverage, and has the largest share of unmet health-care needs due to financial costs. Not only does the USA have high and rising health inequalities, but also life expectancy has stagnated or even declined in some population subgroups. Therefore, the poor recent and projected US performance is at least partly due to high and inequitable mortality from chronic diseases and violence, and insufficient and inequitable health care."

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