Aging is seemingly a simple process through which all humans have to go through during their lifetime. However, aging doesn’t affect everyone in the same way and as you may have noticed some of us age faster than others.
Researchers say there is a reason for that and in a study published in the Proceedings of the National Academy of Sciences an international team of scientists from UK, US, Israel and New Zealand have put forward 18 biological measures that when combined determine whether a person will age faster or slower than others.
Researchers looked at data from a longitudinal study that spanned over 40 decades tracking over 1000 people born in 1972-73 in the same town from birth to the present. The Dunedin study, as it is known, collected regular health data of these people including blood pressure and liver function, along with interviews and other assessments.
First author Dan Belsky, an assistant professor of geriatrics in Duke University’s Center for Aging, said that they wanted to measure aging in young people in contrast to previous studies which have looked into aging of seniors. According to Belsky, the process of aging starts showing its signs in human organs just as it does in eyes, joints and hair, but sooner.
As a part of the regular assessment, when the study population was at the age of 38 in 2011, the team measured the functions of kidneys, liver, lungs, metabolic and immune systems. They also measured HDL cholesterol, cardiorespiratory fitness, lung function and the length of the telomeres — protective caps at the end of chromosomes that have been found 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 proxy for the brain’s blood vessels.
Using these biomarkers, the team set a “biological age” for each participant, which ranged from under 30 to nearly 60 in the 38-year-olds. Then, they went back 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.
Researchers found a variation in the rate of aging, with most of the participants aging at the rate of one year per year, but there were those who were aging three times rapidly i.e. aging three years per chronological year, while there were those who were effectively aging at zero years per year, in effect staying younger than their age.
The researchers, as expected, found that those individuals who were biologically older at age 38 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.
This paper reports on 954 of the original 1,037 Dunedin study participants. Thirty of them had died by age 38: 12 by illnesses such as cancer and congenital defects, 10 by accidents and eight by suicide or drug overdose. Another 26 did not take part in the study at age 38. Twenty-seven participants had insufficient data to be included.
Most people think of the aging process as something that happens late in life, Belsky said, but signs of aging were already apparent in these tests over the 12 years of young adulthood: from 26 to 38.
Study members who appeared to be more advanced in biological aging also scored worse on tests typically given to people over 60, including tests of balance and coordination and solving unfamiliar problems. The biologically older individuals also reported having more difficulties with physical functioning than their peers, such as walking up stairs.
As an added measure, the researchers asked Duke University undergraduate students to assess facial photos of the study participants taken at age 38 and rate how young or old they appeared. Again, the participants who were biologically older on the inside also appeared older to the college students.
The aging process isn’t all genetic. Studies of twins have found that only about 20 percent of aging can be attributed to genes, Belsky said. “There’s a great deal of environmental influence,” he said.
“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, the Nannerl O. Keohane professor of psychology and neuroscience at Duke.
This paper’s methods are merely a proof of concept, Belsky said, to show that it’s possible to see an aging trajectory by combining multiple measures.
“The time is right for this kind of multi-factorial way of measuring the aging process,” he said, but the measures and methods need refinement to be “better, faster and cheaper.”
The ultimate goal, of course, is to be able to intervene in the aging process itself, rather than addressing killers like heart disease or cancer in isolation, Belsky said.
“As we get older, our risk grows for all kinds of different diseases,” he said. “To prevent multiple diseases simultaneously, aging itself has to be the target. Otherwise, it’s a game of whack-a-mole.”
