Emerging longevity diagnostics, Johannesburg
Biological age testing: useful signal or interesting score?
Ageing clocks are among the most talked-about longevity tests and among the least settled. Here is an honest account of what they can and cannot tell you.
In short
Biological-age or ageing-clock tests use combinations of molecular, clinical or wearable data to estimate how an individual's measured biology compares with patterns seen at different chronological ages. They may capture useful risk or physiological information, but they are not a validated diagnosis of ageing, they do not tell a person how long they will live, and different clocks can produce different answers for the same person. At MLI they are treated as emerging adjunctive tools rather than a replacement for established cardiovascular, metabolic and functional assessment.
Medically reviewed by Dr Arnav Kapur, MBBCh Cum Laude
The approach
Understand first. Then treat.
The underlying science is real and genuinely interesting. Patterns of DNA methylation, circulating proteins and routine clinical measures all change with age, and statistical models trained on those patterns can estimate an age-like number. Some of those estimates are associated with disease risk and mortality at population level.
The difficulty is what to do with the number in front of one patient. Reproducibility between assays varies, results shift with the algorithm chosen, and there is limited evidence that acting on a clock result improves outcomes beyond acting on established risk factors. We are willing to discuss these tests, and equally willing to say when they will not add anything to your plan.
What to understand before testing
- What the specific test actually measures, whether epigenetic, proteomic, clinical or wearable-derived
- How the model was trained, and on which populations
- How reproducible the result is if the test were repeated
- Whether the result has been shown to predict outcomes beyond established risk factors
- What decision, if any, the result would change
- Whether established assessment has been completed first
- How the number might be misread, in either direction
- The cost relative to investigations with clearer clinical value
- That regulatory approval for clinical decision-making is generally lacking
What biological age means
Chronological age is a fact; biological age is an estimate produced by a model. Several families of clock exist. Epigenetic clocks read DNA methylation patterns. Proteomic clocks use panels of circulating proteins, and recent work suggests organ-specific versions may carry more information than a single whole-body figure. Clinical or phenotypic clocks combine routine measures such as blood pressure, glucose, lipids, kidney and liver markers and inflammatory indices. Wearable-derived measures add fitness and activity data. Each answers a slightly different question, and none measures ageing itself.
Why different clocks give different answers
A clock reflects the data it was trained on and the outcome it was trained to predict. A model built to predict chronological age behaves differently from one built to predict mortality. Sample handling, assay platform, cell composition in a blood sample and normalisation methods all shift the result, and test-retest variability can be of the same order as the differences people find meaningful. This is why one company may report an age several years below chronological age while another reports the opposite for the same person.
What a biological age result can change
Honestly, often less than people hope. Where a clock result draws attention to something real, it is usually something that established assessment would also have found, such as raised blood pressure, poor glucose regulation, adverse lipids, excess visceral fat, smoking, poor sleep or low fitness. Those findings are actionable on their own terms. A clock result can occasionally be useful as a motivational anchor or to track change alongside proper measures, and that is a legitimate but modest role. It should not be used to start medication, supplements or hormonal treatment.
What matters more than the score
The measures with established links to outcomes are the ones worth investing in: blood pressure control, ApoB and LDL cholesterol, lipoprotein(a) once in adulthood, glucose regulation, not smoking, visceral fat, muscle strength and cardiorespiratory fitness, sleep quality, alcohol intake and appropriate cancer screening. Improving these changes documented risk. Whether an intervention that lowers a clock reading also extends healthy life is not established, and we will not present it as though it were.
Common questions
Answers before you book.
Can biological age be measured accurately?
Not with the precision the marketing implies. Ageing clocks produce an estimate from a statistical model, and repeat testing of the same sample or person can vary by a meaningful margin. They are more informative across populations than for pinpointing one individual's biological age.
Can I reverse my biological age?
A clock reading can certainly change, and it often improves when fitness, weight, sleep, blood pressure and glucose control improve. That is not the same as proof that ageing has been reversed or that lifespan has been extended. The evidence supports the benefit of the underlying changes, not the movement of the score itself.
Which biological age test is best?
There is no established best test, and no ageing clock is approved as a basis for clinical decisions. Different clocks are trained on different data and answer different questions. Rather than recommending a particular product, we would look at what a specific test measures, how reproducible it is and whether the result could change your plan.
Is biological age testing necessary for longevity care?
No. Effective preventative care is built on cardiovascular and metabolic risk assessment, body composition and strength, sleep, screening and treating what is found. Biological age testing is optional and adjunctive, and we are comfortable advising against it when it would not change anything.
This page provides general health information and does not replace individual medical assessment. Biological-age tests are emerging tools that are not validated for clinical decision-making, and they are discussed as optional adjuncts to established assessment.
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Centre of Advanced Medicine, 13 Scott St, Waverley, Johannesburg
Monday to Friday, 07:40 to 17:00
011 440 8721