At the end of last year, Jay Chan, a 30-year-old marine engineer, bought his mother a biological age test from Elysium, a New York-based biotech and health supplements start-up founded in 2014. The test was simple – it required only a saliva sample – and it helped that it was being offered for half off the usual $499 (£400) price.
For fans of the self-described “longevity movement” like Chan, the concept of biological age is liberating. Rather than simply measure the passage of time, biological age aims to quantify the ageing of our body’s functions and even predict mortality. Many scientists and longevity advocates believe this information can not only help us understand our own ageing process, but can give us the power to change it.
Chan felt his mother, Ivy, who is 59 years old, would benefit from knowing her biological age because she was anxious about getting older. “She always talked about entering her 60s and how it’s a big step, and this is the start of fading away,” Chan told me. But with her youthful looks, she still felt healthy. “She looks like a 40-year-old!” he said.
About two months later, they got the results back: Ivy’s biological age was 43.
“It was such a relief for her, because it gives her a newfound hope about life planning,” Chan said. “Knowing how fast she is really ageing, it gives her a renewed sense of self and how she should live in the upcoming decade.”
Dr Steve Horvath, a 54-year-old UCLA professor who pioneered the first “clock” to indicate human ageing by examining chemical changes to DNA, told me that “biological age is a better predictor of morbidity risk than chronological age. It is in some ways a tautology: if it wasn’t better, we wouldn’t call it biological age.”
The hope is that understanding biological age can lead to new life-lengthening interventions. But the first step is to try to measure it, and that’s not straightforward. “Researchers debate how to define it,” said Horvath.
One approach focuses on the length of telomeres, which are protective structures on the ends of our chromosomes, that shorten every time a chromosome replicates – making them an approximate yardstick for biological ageing.
Other approaches take blood samples and measure the presence of molecules that correlate with decreased bodily function. Some approaches even claim to determine mortality risk by scanning people’s eyes.
Horvath’s approach, called the “epigenetic clock”, is considered by many scientists to be the gold standard. Epigenetics is the study of how your environment changes the way your genes work. Horvath’s clock analyzes certain chemical changes to genetic material, a process called DNA methylation. In 2011, Horvath found patterns of DNA methylation could be used to accurately estimate human age.
Horvath compared methylation to sand moving through an hourglass. “As we age, certain parts of the DNA gain methylation and other parts lose methylation. It’s really millions of locations of DNA,” he said.
Horvath’s clock tracks several hundreds of these locations. The result was a formula able to estimate age across a human’s entire life course, from fetus to old age.
Since then, Horvath and other scientists have developed more accurate clocks, based on data collected from the blood samples of the same group of people over many decades. That data helps the clocks to identify unhealthy ageing with greater precision – and, Horvath suggests, “predict time to death”.
If that all sounds complex, it’s perhaps crystalized by the name Horvath gave his second-generation clock: GrimAge, as in the Grim Reaper.
In recent years, these methods have led to an explosion in startups that aim to measure biological age for consumers. These biological age tests are marketed as premium wellness products, often with sleek websites, minimalist packaging and influencer endorsements on social media.
They range in price and testing format: Elysium’s $499 saliva test is based on a biological clock developed by Horvath’s former postdoc, Dr Morgan Levine. “Breakthroughs in ageing research are no longer a myth of science fiction but scientific fact,” the company’s website boasts.
A company called MyDNAge, which claims to offer the “most accurate and reliable DNA Age test”, charges $299 for a blood or urine test that uses a licensed version of Horvath’s clock.
There are popular but less expensive options that don’t use epigenetic clocks, such as Thorne’s biological age test, which costs $99 and requires a trip to a third-party lab to give a blood sample.
None of these tests have been approved by the FDA.
I tried to buy a biological age test from Thorne, but found out that I wasn’t allowed to order one due to laws in New York, which is among a handful of US states that restrict or prohibit “direct access” medical tests. But in most states, you can order a biological age test online as long as you’re over 18 and have a credit card.
Horvath has mixed feelings about the tests’ popularity. “Currently these clocks are not useful for the average person because we don’t have an intervention to slow ageing,” he said. “Let’s say a medical doctor orders an epigenetic clock test, and it indicates a patient is older than they should be, what should the doctor say? There’s no cure they can prescribe,” beyond repeating conventional health advice.
He started a non-profit foundation called the Clock Foundation, “because I wanted to insure rigor. I was very worried that these tests will not be properly implemented.” As the popularity of biological age tests boomed, he “very reluctantly” decided to offer tests to the public as well, “because the horse is out of the barn”.
Could biological age become another stressful number for people, on top of the many health indicators – weight, blood pressure, daily steps – they already worry about? Horvath said there was a danger that people might misinterpret their results. “But I think I’m a big believer in freedom, and I like measuring things about myself,” he said.
Last year he performed the GrimAge test on himself, and found his biological age was four years older than his chronological age. “I will not jump to the conclusion that I will live four years less. Because humans are so complicated, and things can change.
“I can interpret it and take it with a grain of salt. I can say, you know what, my GrimAge is four years older, but actually I have really good blood pressure.”
But the analysis can be tricky for untrained test-takers – like Ed, a 29-year-old graduate student and self-described “biohacker” whom I met through a forum for longevity enthusiasts.
Ed was in college when he began researching ways to improve his own biology, “probably to try to get fit to attract girls”. But the research led him to grow concerned about ageing. “It’s bittersweet when you’re into fitness, combing through scientific articles trying to optimize your performance and knowing that you’re at your prime – it’s only downhill from here.”
Two years ago, he took a biological age test through MyDNAge, which analyzed his blood sample using a version of Horvath’s epigenetic clock.
The test told him he was biologically 23 – which he was unsure how to interpret. “I was in good physical shape and a relatively healthy non-smoker but I’d also started to lose my hair very young. Was this a sign of accelerated ageing?” he wondered.
He felt pleased anyway. “I take consolation in knowing that if it ends up being useless then at least it’s taking down an academic gold-standard analytical technique with it,” he said.
Ed said it can be “very difficult and complicated” to sort through all the marketing in the growing longevity industry. He occasionally reads academic papers about ageing and listens to longevity-themed podcasts, but “so much what is out there is heavily promoted snake oil”.
He’s been taking vitamins, limiting his caloric intake, and fasting – but hasn’t asked his doctor for advice. “I don’t think my PCP would even know where to start honestly. I think there is a huge knowledge gap between practicing doctors and bleeding-edge research.”
Horvath said for now, consumers should “think of it more as entertainment. People are curious, they want to brag to their friends that they’re younger, then why not?”
His dream is that the biological age tests will become reliable enough that future doctors will be able to make specific recommendations based on them. “But we’re just not there yet,” said Horavth.
But there is some practical advice: Horvath said the data from the clocks has validated “everything we already know” about what leads to long lifespans.
“If I was an alien from Mars arriving on planet Earth and I used epigenetic clocks, it would basically recapitulate 50 years of epidemiologic research. It would say smoking is terrible for you. It would say obesity is bad for you. It would say eat vegetables. It would say exercise.”
That’s validating news for test takers like Ivy Chan.
“Before the test, she exercised, but now she really makes sure to exercise regularly and eat healthy,” said her son. “She also started to learn another language, because why not?
“She thought maybe she had another 20 or maybe 30 healthy years, but now it seems like that’s gonna be 40 or even 50 if we are lucky.”
