Many older clocks compare the natural age of a person to epigenetic markers, in particular, the tags of methyl groups that are embedded in DNA and affect genetic expression. The mechanism of this methylation on thousands of websites on DNA seems to change as we age, although the cause is not known.
Some watches promise to predict life expectancy by comparing the human aging process, while others serve as an indicator of speed, tracking and aging. Clocks have been developed for specific body parts, as well as for several species of animals.
Proponents of aging are already trying to use them to show that anti-aging techniques can make people naturally younger. But we still do not know much about mechanics, or what they tell us, to say the least.
The first old epigenetic clock was developed in 2011 when Steve Horvath of the University of California, Los Angeles, volunteered to do research with his twin brother, Markus. The study was looking at epigenetic markers in saliva samples that could articulate preferences. (Steve is straight and Markus is gay.)
As a biostatistician, Horvath volunteered to evaluate the results and did not find any sexual orientation. But he also looked at links between years of commitment and epigenetic writing. “I fell off my chair, because the sign was so old,” he says.
It was found that methylation patterns can predict a person’s age in years, although the figures vary about five years from the age of each person.
Horvath has been working on old clocks ever since. In 2013 he developed the famous Horvath watch, which is one of the most popular old-fashioned watches of today, called the “pan-tissue” watch because it can compare the age of each organ in the body. Horvath designed the clock using methylation data from 8,000 models representing 51 body tissues and cell types. With this data, he taught an algorithm to predict the age of a person from a cell.
Other groups have developed similar clocks, and hundreds of them exist today. But Horvath estimates that at least 10 are used more extensively in human studies, especially to see how diet, lifestyle, or supplements can affect aging.
What can all these clocks tell us? It depends. Many clocks are designed to predict the ages. But Morgan Levine of Yale School of Medicine in New Haven, Connecticut, said: “For me, that is not the point. We can ask someone how old they are. ”
In 2018, Levine, Horvath, and colleagues developed a clock based on nine biomarkers, including the amount of sugar in the blood and white blood cells, as well as human age.
They used data collected from thousands of people in the US as part of a separate study, which followed students for many years. The incoming clock, called DNAm PhenoAge, is better suited to comparing natural age than mechanical timepieces, says Levine.
A one-year increase in what Levine calls “phenotypic” years, according to the clock, is associated with a 9% increase in deaths from any cause, as well as an increased risk of dying from cancer, diabetes, or heart disease. If your age is higher than your age, it is best to assume that you are getting older faster than average, says Levine.
But that is not the case, says Daniel Belsky at Columbia University Mailman School of Public Health in New York City. He says there are many reasons why natural age can exceed human life.
Belsky and colleagues have developed a tool to accurately measure the rate of natural aging, using a project that tracked the health outcomes of 954 volunteers over four years between the ages of 20 and between 40s. The researchers looked at biomarkers that are believed to show how different organs function, as well as other health-related factors. Then he developed a speedometer that showed how these things would change over time.
Another popular watch, also made by Horvath and his associates, is called GrimAge, courtesy of Grim Reaper. Horvath says it is the best way to predict death, and he has been using it in his blood tests.
The results were in line with his age two years ago, he says, but when he took another test six months ago, his GrimAge was four years older than he was. That doesn’t mean Horvath has shaved four years from his lifespan – “You can’t directly relate to the time you’re going to live,” he says – but he thinks it means he’s getting older faster than he should be, though he still surprises. the reason.
Some have used the modification of their results to ensure that their aging is reduced, usually as soon as they start taking the supplement. But in many cases, this change can be explained by the fact that many older epigenetic clocks are “noisy” – they can make random mistakes that interfere with their results.
The problem is that in each part of the body where methyl groups connect to DNA, small changes occur over time. These hidden mutations can be amplified by errors in methylation comparisons. It is a serious problem, says Levine, and its effects can last for years.