You know your field of research has hit the mainstream when it appears on The Kardashians, and so it was with mixed feelings that longevity scientists saw Khloé screaming with excitement as she opened the results of a biological age test on the show. Khloé is chronologically 40, but her biological age according to an ‘epigenetic clock’ was just 28 years old.
There are various tests that you can try at home, ranging from how you look, to tests of physical fitness, to hearing. How do they work, are they any good, and how do they compare to the more scientific-seeming alternatives involving blood tests and DNA data?
Here are five ways to find out how biologically old you are.
1. Perceived facial age
But these tests of biological age can run into hundreds of dollars. So, if you want to keep up with the Kardashians, but without shelling out for one of these tests, how can you get a measure of your biological age – ideally for free?
It’s simultaneously surprising and totally unsurprising that how old you look is a reasonable measure of how old you are. We all know people who have waltzed into their 60s with smooth skin and a spring in their step, and other 60-somethings who are already looking haggard and feeling frail.
A study published in 2009 transformed vibes into scientific rigour – looking younger really could mean you are younger, biologically speaking.
The study included almost 1,000 pairs of twins over the age of 70, and asked panels of assessors to rate how old they looked. The somewhat morbid outcome was that older ‘perceived facial age’ was an accurate predictor of which twin would die first.
The reason for this is that the biological mechanisms that drive ageing of the skin have a lot in common with those driving ageing in the rest of the body. We now understand that the same ‘hallmarks of ageing’, ranging from damage to the DNA in our cells to dysfunction of our immune systems, are behind everything from cancer risk, to frailty, to the external signs of growing old, like wrinkles and grey hair.
Collagen, the primary structural protein in our skin, is also a vital component of our blood vessels and bones, and saggy skin suggests saggy arteries and weakening bones and joints within.
If you want to measure your facial age, you’ll need to get a panel of neutral assessors to pass judgement on your appearance – it’s pretty likely that you aren’t the most objective judge of your own face.
There are also various apps that claim to do this using artificial intelligence (AI), which is a promising high-tech way to do this – but always take care of your data: think carefully about who’s behind the website or app before uploading a selfie.
There are, of course, various ways to cheat on this particular test, some more useful than others. Purely cosmetic approaches like make-up, Botox and fillers don’t impact on the underlying biology of skin ageing.
Sun protection is a far more promising approach: avoiding Sun exposure during the brightest parts of the day, and wearing a hat and suncream when you do go out will prevent UV rays from accelerating some of those ageing hallmarks. By protecting the collagen and DNA in your skin, Sun protection reduces wrinkles and cancer risk by keeping skin truly younger in a biological sense.
Of course, being Sun smart doesn’t affect the ageing of your internal organs directly so – while well worth paying attention to in order to keep your skin both youthful looking and healthier – it could make how old we look a less reliable predictor of overall health.
2. Standing-on-one-leg age
Many of our physical abilities gradually worsen with age, and one of these is our sense of balance. Accordingly, a very simple measure of biological age is how long you can stand on one leg for. (Doctors call this the ‘timed unipedal stance balance test’ in an attempt to make it sound more sciencey.)
To try this at home, simply fold your arms, stand on your dominant leg (the one you’d use to kick a football), and start a timer. If you uncross your arms or move either of your legs (like rotating your foot on the floor to maintain balance), or of course if you lose balance completely, that’s your time! And, if you fail completely on the first attempt, don’t worry: it’s best of three.
The researchers behind a study that tested this stopped the clock at 45 seconds, so if that’s too easy you might want to try with your eyes closed. Even the youngest 18–39 group only managed 15 seconds, while over-80s lost their balance or opened their eyes after just two.
To find your biological age from your standing time, you can use the graph below. Simply move across from the appropriate time until you hit the line for eyes open or closed, and then go straight down. So, say you manage 13 seconds with your eyes closed, that corresponds to a standing-on-one-leg age of 45 years old.
One of the big advantages of so-called ‘functional’ tests of biological age (others include grip strength, ability to stand up unassisted from a sitting position, and so on) is that they get at something that’s actually useful in everyday life. Perhaps you don’t find yourself teetering on one leg so often in your day-to-day, but the test requires a number of body systems to work together.
For example, your sense of balance, mediated in large part by sensors in your inner ear; muscle strength, to support your bodyweight and continuously shift it slightly to avoid toppling over; and the neuromuscular connections that allow your sense of balance and muscles to communicate to do all this in real-time. You’ll use all of these while you walk, stand up and sit down, and many other practical activities.
A sense of balance and the strength to employ it are also very important because one of the leading causes of death and disability in older people is falling.
About a third of older people who fall and break their hip die within 12 months – most of them not from the fall itself, but because the physiological stress of the fracture and extended recovery period can exacerbate other health problems. If you’ve got better balance, you’re more likely to recover from a stumble and not fall in the first place – and that could save your life.
Practising to improve your standing-on-one-leg age could be genuinely useful, but it also illustrates an issue with many of these measures. In lots of cases, you can essentially ‘cram for the test’ by, in this case, taking a few minutes out of your day to do some balance exercises.
It’s probably obvious, but nonetheless worth saying: just because you can stand on one leg for five minutes, it doesn’t mean you’re biologically immortal – the data here were gathered in people who hadn’t been specifically training for it!
Is having better balance really the same as ‘reducing your biological age’? It will certainly improve some aspects, and could even make you live longer if it helps avoid a fall, but it’s relatively unlikely that spending a few minutes a day on one leg will alter the ageing of your immune system, for example.
So, when it comes to trying to get biologically younger, this is a good way to remember not to obsess over optimising a single measure – you have to, if you’ll excuse the pun, strike a balance.
3. Fitness age
Exercise is one of the best things you can do for your general health and, accordingly, measures of cardiovascular fitness are also useful measures of biological age.
Perhaps the most-mentioned measure at the moment is VO2 max: the maximum volume of oxygen your body can consume when exercising all-out. Given this definition, a proper VO2 max test is brutal: you visit a lab, strap on a face mask that can measure how much oxygen you’re breathing in, and then run on a treadmill or cycle a stationary bike, gradually getting faster until you run out of gas – literally.
The good news for anyone who doesn’t want to undergo this exhausting and expensive lab test is that many smartwatches and other wearables can estimate your VO2 max if you wear them while walking or running.
The reason for its sudden popularity is the observation that VO2 max is a very strong predictor of future health: a study in 2018 found that people in the bottom 33 per cent of the population for VO2 max were almost twice as likely to die as people in the top third.
VO2 max also decreases with age, halving from 42ml/kg/minute for an average woman in her 20s to just 21ml/kg/minute in an 80-something female. If you’re looking to improve your score, exercise is the key - research shows a 65-year-old who exercises their way into the top 25 per cent for their age group could have a VO2 max equivalent to an average person in their 30s.
It’s worth noting that the smartwatch-based estimates of VO2 max often aren’t perfectly accurate, and can vary by maybe 10 per cent either way – enough to add or subtract a decade from your VO2 max age!
Thus, if your watch is telling you you’re older than you are, don’t fret: the most important thing to do is to watch the trend in the values your device reports, rather than worrying too much about the absolute value. If the VO2 max your watch reports is climbing, it’s pretty likely your fitness is too.
If you don’t own a smartwatch, there’s also an online calculator for fitness age developed by Norwegian researchers, which just needs your chronological age, weight, height, resting heart rate and an estimate of your exercise level to work out how biologically old you are.
Both this and VO2 max tell the same basic story: exercising more will improve your fitness age (both directly since it considers how often you exercise, and by improving your resting heart rate), as well as your VO2 max. So, anything from a five-minute brisk walk to the recommended daily half-hour of moderate to vigorous exercise can start you on the journey to biological youth.
4. Hearing-the-high-notes age
The typical range of human hearing is often quoted as 20–20,000Hz, meaning that we can hear vibrations that wobble between 20 and 20,000 times per second. 20Hz sounds are deep, almost rumbling (the bottom note on a standard piano is called A0, and is 27.5Hz), while 20,000Hz is a barely audible high-pitched squeal (and would require a piano with an extra 27 keys on the high end to get anywhere near).
However, nice though those round numbers are, they’re not accurate for most of you humans reading this. If you’re a teenager or younger, it’s quite possible that your hearing extends above 20,000Hz, while those of us who are older will experience the top end of our hearing slowly declining as the decades pass – if you can’t hear sounds over about 11,000Hz, your hearing age is over 50 years.
This is primarily due to a gradual loss of sound-sensing hair cells in our inner ear with age – and assessing these changes can give us another measure of biological age.
Hearing loss can be anything from socially isolating at dinner parties to dangerous when crossing the road. And there’s even evidence that it can lead to loss of brain function: people who lose their hearing are at increased risk of dementia, while those who catch the problem and compensate for it with hearing aids can actually reduce their risk of cognitive decline.
So, how can you measure your hearing age? The proper way is to visit an audiologist (a doctor specialising in hearing and hearing loss), who can administer tests where you’ll pop on a pair of headphones and be played a variety of sounds, including sounds of different frequencies, to test for age-related hearing loss.
There’s also a range of tests available online that claim to measure your hearing age, usually by playing a note that gets higher along with a number that, at the moment you can no longer hear the sound, indicates your biological age.
While interesting, these are probably best regarded as a bit of fun – without properly calibrated headphones, a truly silent test environment, and so on, you’re probably not going to get a completely accurate answer. Another problem is compressing audio and video online to save on data usage can sacrifice exactly the high frequencies we’re testing for!
The other factor is that just finding the top end of your hearing spectrum doesn’t tell you that much about the things that matter for everything, from day-to-day life to dementia risk. Perhaps the best thing to do if you’re worried about hearing loss at any age is to try the test from UK-based hearing loss charity the Royal National Institute for Deaf People (RNID).
It doesn’t spit out a satisfying hearing age number but, if it does flag up potential hearing loss, treatment could improve your brain age – as well as making dinner parties more enjoyable.
5. BLOOD TESTS AND EPIGENETIC AGE
While functional tests are the gold standard in one way – they measure things that actually matter in everyday life – they clearly can’t capture every aspect of the ageing process. That’s where the more molecular measures of biological age can hopefully step in, coming up with measures based on results of blood tests, or measures of ‘epigenetic marks’ on your DNA.
Perhaps the most famous of these is the ‘Horvath clock’, developed in 2013 by scientist Steve Horvath. He was looking at a particular kind of DNA modification called ‘methylation’, a type of epigenetic mark that turns different parts of the DNA on or off as they’re needed.
He used machine learning to create an astonishingly accurate biological clock – it could predict someone’s age to within about four years, using a sample from any tissue in their body.
The fact these clocks don’t always come back with the number of candles on your birthday cake raises a question: should Khloé Kardashian chalk the 12-year discrepancy in her biological age up to random measurement error, or does it indicate that she’s truly biologically younger, and therefore at lower risk of disease and early death than had her result come back as a less flattering 52 years old?
In the intervening decade, further research has shown that these discrepancies are indeed meaningful, and being epigenetically older indicates a higher risk of disease and death. Scientists have also developed other clocks based on blood tests, sugary modifications to proteins and more, with similar results.
And of course these tests have also escaped the lab onto our TV screens. There are now quite a number of companies who will happily take a small blood sample or cheek swab (and several hundred dollars) to tell you your biological age.
Unfortunately, while these clocks are a fascinating research tool, it’s harder to see the benefit for consumers (or Kardashians) at present.
The problem is, while these clocks probably are capturing something more general about the ageing process than how long you can stand on one leg for, it’s not entirely clear yet what that is. Meaning: if your result comes back and you’re biologically ancient, the advice will broadly be the same health tips I’d give you if your result came back the same as your normal age, or even younger.
While it might not be worth a few hundred dollars to find out your biological age, an alternative you might be able to try at home is to use blood test results.
One age calculator, called PhenoAge, uses nine common blood tests to tell you how biologically old you are. While it’s probably not worth going out and getting these tests done specifically for the purpose, you might already have most or all of these in your medical record, and can simply tap them into an online calculator to find out your biological age for free.
Whether based on blood tests or epigenetics, where these biological age tests will really shine is when we start developing drugs to slow down the ageing process. The problem with testing a treatment to improve longevity is that the clinical trial could take decades – and maybe even longer if it works!
However, once we understand a bit more about what these measures are really measuring, we could potentially do clinical trials in months rather than years, by doing a before-and-after biological age test to see if the new treatment works.
This means they’ve got the potential to make real anti-ageing medicine arrive much sooner – maybe soon enough that you’ll celebrate your 80th birthday by losing your balance after five minutes stood on one leg because of a very loud sound at 20,000Hz.
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