Biological Aging Tests are Not Yet Useful for Individual Insights
Why I'm Not Using Biological Aging Tests (Yet) 🕰️ 🧬
In practice, when working with clients and selecting appropriate interventions, two of my guiding rules are:
Where possible and practical, test, don't guess, to guide an intervention or validate an outcome.
DON'T test if the results will not give you reliable, actionable insights.
Biological aging clocks are increasingly marketed and interest is rising. I'm also getting asked about them.
But that second rule is why, for now, I wouldn't recommend a biological aging test.
Entertaining? Yes ✅
Useful in research? Yes ✅
Actionable insight for one person? Not yet ❌
Potentially demotivating or distressing? For some people, yes 😔
Biological Aging Tests: What Do They Actually Tell Us?
A recent paper, "Do we actually need aging clocks?", published in the journal NPJ Aging, very nicely captures some of the issues around using biological aging clocks in clinical practice.
Here are the main concerns.
1. Biological age is not a directly measurable thing
"Biological age" is an abstract value produced by an algorithm.
Different biological aging clocks define and calculate it differently, depending on the data they use and their modelling approach.
So when someone is told:
"Your biological age is 52"
that number isn't measuring a physical characteristic in the same way that your height, blood pressure or blood glucose can be measured.
It's an estimate generated by a particular model.
2. Correlation with chronological age is not enough to be useful
A clock can accurately predict someone's chronological age without meaningfully predicting disease, physical function, frailty or lifespan.
We already know the person's chronological age.
So if a test simply tells us that someone who is 52 has biological characteristics associated with being 52, what additional value have we gained?
For a clinical test, I'd want considerably more.
3. Results are often inconsistent
Different ageing clocks can produce different conclusions about the same intervention.
In the CALERIE calorie-restriction trial, for example, some clocks suggested slower ageing while others showed no meaningful effect.
That raises an important question:
Which result should we believe?
And there is another issue that I find particularly concerning.
Some practical experiments, including by Dr Matt Kaeberlein, have indicated substantial inconsistency between results, including results from the same test performed at similar times.
We can also call this the:
"Eating a burger for lunch shouldn't change your biological age" problem. 🍔🤤
If a test produces a meaningfully different biological age simply because of short-term variation in diet, exercise, sleep, stress or other factors, how useful is that number for measuring long-term biological ageing?
4. Correlation does not prove causation
This is a fundamental principle in interpreting biomarkers.
A biomarker associated with faster ageing may be a passenger rather than a driver.
In other words, it may be associated with an underlying process without actually causing the resulting health outcome.
That means changing the biomarker does not necessarily mean we've improved health.
For a test to guide an intervention, I'd want evidence that changes in the measurement are meaningfully connected to changes in outcomes that matter.
5. Uncertainty is often under-reported
Many biological aging clocks provide a single number.
But a single number can create a false impression of precision.
I'd want to know:
How reliable is the result?
What is the confidence interval?
How much does the result vary between tests?
How much variation is expected within the individual?
How much variation comes from the testing process itself?
Does a change in the number actually represent a meaningful change in health?
Without this context, telling someone their "biological age" risks making an inherently uncertain measurement appear much more definitive than it really is.
What Would Make Me Change My Mind?
Given the ongoing work in this area, I can imagine a biological aging clock becoming available that is clinically useful.
I'd welcome it.
It would be fantastic to have a reliable way of validating whether interventions designed to improve healthspan are actually working.
But I'd want to see a clock demonstrate:
🎯 Accuracy
📋 Reproducibility, consistent results when the test is repeated under appropriate conditions.
🔎 Transparency, a clear understanding of how the measurement is generated and what its limitations are.
🔗 A meaningful link to outcomes., for example, health endpoints, physical function, disease risk or other outcomes that actually matter, rather than simply another biomarker.
Test, Don't Guess but Don't Test for the Sake of Testing.
This is really the principle behind my current position.
I'm a strong believer in using appropriate testing where it can provide useful information.
Testing itself isn't the goal. Actionable information is the goal.
If a test gives us reliable information that can help us make a better decision, change an intervention or validate an outcome, it can be extremely valuable.
If it gives us an impressive-looking number without sufficient confidence that the number is meaningful,
I'm not convinced that it belongs in routine practice yet.
For now, biological aging clocks remain an interesting area of research rather than a test I'd routinely recommend to clients.
I hope that changes.
Because a genuinely reliable way to measure biological ageing and validate improvements in healthspan could be incredibly useful.
Have You Used a Biological Aging Clock?
Have you used one, or been tempted to?
Are you currently holding off for the same reasons?
My clients enjoy clear, specific, actionable guidance on how to use diet, supplementation, lifestyle and functional testing to reach their personal health goals and resolve their health issues.
Why not book a Personal Health Strategy call to find out how we would enable better health for you? 📲
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