If you’ve ever been to a high school reunion, you probably looked around at your former classmates and wondered how could some people look so much older or younger than others. Do some people just age faster?
According to the leaders of a major long-term health study in New Zealand that has sought clues to the aging process in young adults, yes, they do.
In a recently published paper, the team proposes a collection of 18 biological measures that may be combined to determine whether people are aging faster or slower than their peers.
The data came from the Dunedin Study, a breakthrough longitudinal study that has tracked more than a thousand people born in 1972-73 in the same town from birth to the present. Health measures like blood pressure and liver function have been taken regularly, along with interviews and other assessments.
First author Dan Belsky, assistant professor of geriatrics in Duke University’s Center for Aging, said:
“We set out to measure aging in these relatively young people. 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 progress of aging, Belsky comments, shows in human organs just as it does in eyes, joints, and hair, but sooner. So as part of their regular reassessment of the study population at age 38 in 2011, the team measured the functions of lungs, liver, kidneys, and metabolic and immune systems.
They also measured lung function, cardiorespiratory fitness, HDL cholesterol, and the length of the telomeres, the protective caps at the end of chromosomes which are known to shorten with age.
The study also measures dental health and the condition of the tiny blood vessels at the back of the eyes, which are a marker for the brain’s blood vessels.
The research team set a “biological age” for each participant, based on a subset of these biomarkers, which ranged from under 30 to nearly 60 in the 38-year-olds.
Then, researchers returned to the archival data for each subject and looked at 18 biomarkers that were measured when the participants were age 26, and again when they were 32 and 38. From this, they drew a slope for each variable, and then the 18 slopes were added for each study subject to determine that individual’s pace of aging.
Most participants clustered around an aging rate of one year per year, but others were found to be aging as fast as three years per chronological year. Many were aging at zero years per year, in effect staying younger than their age.
As the team expected, those who were biologically older at age 38 also appeared to have been aging at a faster pace. A biological age of 40, for example, meant that person was aging at a rate of 1.2 years per year over the 12 years the study examined.
Usually we think of the aging process as something that happens late in life, Belsky says, but signs of aging were already apparent in these tests over the 12 years of young adulthood: from 26 to 38.
Also, the aging process is not all down to genetic factors. Studies of twins have found that only about 20 percent of aging can be attributed to genes, Belsky says. “There’s a great deal of environmental influence.”
The final objective, of course, is to intervene in the aging process itself, instead of continually fighting off killers like heart disease or cancer in isolation, Belsky says.
Daniel W. Belsky, Avshalom Caspi, Renate Houts, Harvey J. Cohen, David L. Corcoran, Andrea Danes, HonaLee Harrington, Salomon Israel, Morgan E. Levine, Jonathan D. Schaefer, Karen Sugden, Ben Williams, Anatoli I. Yashin, Richie Poulton, and Terrie E. Moffitt
Quantification of biological aging in young adults
PNAS July 6, 2015 doi: 10.1073/pnas.1506264112