An international team says there may be a reason why some people seem to stay young well into their dotage.
Researchers from the U.S., Britain, Israel and New Zealand observed that at the physical age 38, the biological age of individuals was all over the map. Some 38-year-old bodies were still in their 20s, while others were nearly 60.
Dan Belsky, a professor of geriatrics at Duke University’s Center for Aging and a study author, said the findings — that people decline faster or slower physically beginning at a relatively young age — go counter to what is commonly believed.
A second surprise, he said, "was how much variation in that change there was in that population. People really did age very slowly or very rapidly.”
Investigators analyzed data from the Dunedin Study, a long-term health study in New Zealand seeking clues to factors involved in aging.
Eighteen biomarkers, including blood vessel integrity, kidney and liver functions, measurements of metabolism and immunity, were measured in a group of 1,000 people beginning at age 26. The health biomarkers were taken again when the participants were age 32 and again at 38.
A calculation based on the readings was developed to determine each volunteer’s pace of aging. Then, Belsky said, tests usually reserved for older individuals were given to the participants.
“We tested their balance, we tested their strength, we tested their motor coordination," he said. "We interviewed them about physical limitations they may have, having trouble climbing stairs, carrying groceries, walking a mile. And we also gave them some cognitive tests. And what we saw was that the study numbers we had measured to be aging faster were having more physical problems; they were weaker, they had poor balance, they were not as coordinated. And they were more likely to report physical limitations. And they are still 38 years old and mostly free of any chronic disease.”
Then, researchers conducted what was in some ways the ultimate litmus test of aging: They asked college students to look at pictures of the participants.
"They rated those faces as either looking young or looking old," Belsky said. "And the very same study numbers we had measured to be aging very rapidly were also rated by the Duke undergraduates as looking older.”
The findings were published in the journal Proceedings of the National Academy of Sciences.
By studying the rate of aging, investigators hope they can get a jump on some age-related diseases earlier in people's lives.