Bad habits have eroded the edge that Americans had 40 years ago over Western Europeans in terms of life expectancy.

The culprits? Primarily smoking and obesity-related diseases such as hypertension and diabetes.

Americans now live about a year-and-a-half less than Western Europeans, and also less than people in most other developed nations, according to a new study funded by the U.S. Department of Labor, the National Institute on Aging and the MacArthur Research Network on Aging.

Life expectancy in America starts to deteriorate around the age of 50, according to study researchers from the University of California, the RAND Corp. and the Harvard School of Public Health. But if aging people develop better health habits, they estimate, by the year 2050 health-care costs could be reduced by more than $17,800 per person, or more than $1.1 trillion.

The researchers compared health habits and life expectancy in the United States with that of Denmark, France, Germany, Greece, Italy, The Netherlands, Spain and Sweden. The study was published in the July issue of Social Science & Medicine.

According to the U.S. Department of Health and Human Service's Administration on Aging, in 2009, at age 65, an American woman could expect to live another 19.9 years, while a man could expect 17.2 years. Although it's impossible to predict exactly how long people will live in the future, the agency projects that by 2050, women at 65 will have anywhere from 15.3 to 25.2 years left, while men could live another 15.8 to 26 years.

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