American Life Expectancy Growing: Here's Why

Americans appear to be aging slower than they used to, which may help explain recent gains in life expectancy, researchers say.

The researchers compared how biological age changed in the United States compared to age in years (chronological age). For the study, the investigators looked at national health surveys conducted 1988-1994 and 2007-2010.

"This is the first evidence we have of delayed 'aging' among a national sample of Americans," study senior author Eileen Crimmins said in a University of Southern California news release. Crimmins is a professor of gerontology at USC.

The study suggests that the explanation for recent gains in life expectancy goes beyond simply keeping sick people alive.

To calculate biological age, the researchers used several benchmarks for metabolism, inflammation, organ function, blood pressure and breath capacity.

While all age groups had a decrease in biological age, not all people were faring the same.

Older adults had the greatest decreases in biological age, and men had greater declines than women.

These differences were partially explained by changes in smoking, obesity rates and medication use, according to the study, which was published recently in the journal Demography.

Lead author Morgan Levine is an assistant professor at Yale University's Center for Research on Aging.

"While improvements may take time to manifest, and thus are more apparent at older ages, this could also signal problems for younger cohorts, particularly females, who -- if their improvements are more minimal -- may not see the same gains in life expectancy as experienced by the generations that came before them," Levine said.

The findings suggest that improving healthy behaviors and using prescription medications will have significant effects on Americans' health.

But the researchers noted that the pace of aging and increasing life expectancy could also have big social and economic consequences.

"Life extension without changing the aging rate will have detrimental implications. Medical care costs will rise, as people spend a higher proportion of their lives with disease and disability," Levine said.

But, she added, extending life span by slowing down the aging process should reduce health care costs and lead to higher productivity and greater well-being.