Aging is typically studied in the elderly, but a study released Monday said different rates of aging in people can be detected as early as their mid-20s.
"We set out to measure aging in these relatively young people," the study's first author, Dan Belsky, an assistant professor of geriatrics at Duke University's Center for Aging, said in a press release. "Most studies of aging look at seniors, but if we want to be able to prevent age-related disease, we're going to have to start studying aging in young people."
The findings, in the most recent issue of The Proceedings of the National Academy of Sciences, are based on a group of 954 people born in New Zealand in 1972 or 1973.
Researchers said the progress of aging shows up in human organs sooner than it does in eyes, joints and hair. Because of that, they collected data on the subjects' kidney, liver and lung function, dental health, blood vessels in the eyes, metabolism and immune system function at age 26, 32 and 38.
They also measured cholesterol, fitness levels and the length of telomeres, the protective sections at the end of chromosomes that have been found to shorten with age.
Using 18 biological measurements, researchers determined a "biological age" for each participant at age 38, with some registering under 30 and others appearing to be nearly 60.
When scientists looked closely at the ones who aged more quickly, they found signs of deterioration were apparent at age 26, when the first set of biological measurements were taken.
Most study subjects were aging at the expected rate of one biological year per chronological year. Some were aging more slowly, and others were aging as quickly as three biological years per chronological year.
Those whose bodies were aging faster "scored worse on tests typically given to people over 60, including tests of balance and coordination and solving unfamiliar problems," the study said. The biologically older individuals also had more difficulties than their peers with activities such as walking up stairs.
And when university students at Duke were asked to look at pictures of people in the study group, they consistently rated as older those whose bodies were aging more quickly than the others'.
Study authors said their findings pave the way for future tests that may be easier and cheaper to implement, so that people can find out how fast they are aging in their 20s, when they might be able to do something about it and possibly prevent age-related diseases.
Previous research has shown that genes account for only about 20 percent of aging, leaving the rest up to health behaviors and the environment.
"That gives us some hope that medicine might be able to slow aging and give people more healthy active years," said senior author Terrie Moffitt, a professor of psychology and neuroscience at Duke University.
Al Jazeera and wire services