We all like to imagine we’re ageing well. Now a simple blood or saliva test promises to tell us by measuring our “biological age”. And then, as many have done, we can share how “young” we really are on social media, along with our secrets to success.

While chronological age is how long you have been alive, measures of biological age aim to indicate how old your body actually is, purporting to measure “wear and tear” at a molecular level.

The appeal of these tests is undeniable. Health-conscious consumers may see their results as reinforcing their anti-ageing efforts, or a way to show their journey to better health is paying off.

But how good are these tests? Do they actually offer useful insights? Or are they just clever marketing dressed up to look like science?

How do these tests work?

Over time, the chemical processes that allow our body to function, known as our “metabolic activity”, lead to damage and a decline in the activity of our cells, tissues and organs.

Biological age tests aim to capture some of these changes, offering a snapshot of how well, or how poorly, we are ageing on a cellular level.

Our DNA is also affected by the ageing process. In particular, chemical tags (methyl groups) attach to our DNA and affect gene expression. These changes occur in predictable ways with age and environmental exposures, in a process called methylation.

Research studies have used “epigenetic clocks”, which measure the methylation of our genes, to estimate biological age. By analysing methylation levels at specific sites in the genome from participant samples, researchers apply predictive models to estimate the cumulative wear and tear on the body.

What does the research say about their use?

Although the science is rapidly evolving, the evidence underpinning the use of epigenetic clocks to measure biological ageing in research studies is strong.

Studies have shown epigenetic biological age estimation is a better predictor of the risk of death and ageing-related diseases than chronological age.

Epigenetic clocks also have been found to correlate strongly with lifestyle and environmental exposures, such as smoking status and diet quality.

In addition, they have been found to be able to predict the risk of conditions such as cardiovascular disease, which can lead to heart attacks and strokes.

Taken together, a growing body of research indicates that at a population level, epigenetic clocks are robust measures of biological ageing and are strongly linked to the risk of disease and death

But how good are these tests for individuals?

While these tests are valuable when studying populations in research settings, using epigenetic clocks to measure the biological age of individuals is a different matter and requires scrutiny.

For testing at an individual level, perhaps the most important consideration is the “signal to noise ratio” (or precision) of these tests. This is the question of whether a single sample from an individual may yield widely differing results.

A study from 2022 found samples deviated by up to nine years. So an identical sample from a 40-year-old may indicate a biological age of as low as 35 years (a cause for celebration) or as high as 44 years (a cause of anxiety).

While there have been significant improvements in these tests over the years, there is considerable variability in the precision of these tests between commercial providers. So depending on who you send your sample to, your estimated biological age may vary considerably.

Another limitation is there is currently no standardisation of methods for this testing. Commercial providers perform these tests in different ways and have different algorithms for estimating biological age from the data.

As you would expect for commercial operators, providers don’t disclose their methods. So it’s difficult to compare companies and determine who provides the most accurate results – and what you’re getting for your money.

A third limitation is that while epigenetic clocks correlate well with ageing, they are simply a “proxy” and are not a diagnostic tool.

In other words, they may provide a general indication of ageing at a cellular level. But they don’t offer any specific insights about what the issue may be if someone is found to be “ageing faster” than they would like, or what they’re doing right if they are “ageing well”.

So regardless of the result of your test, all you’re likely to get from the commercial provider of an epigenetic test is generic advice about what the science says is healthy behaviour.

Are they worth it? Or what should I do instead?

While companies offering these tests may have good intentions, remember their ultimate goal is to sell you these tests and make a profit. And at a cost of around A$500, they’re not cheap.

While the idea of using these tests as a personalised health tool has potential, it is clear that we are not there yet.

For this to become a reality, tests will need to become more reproducible, standardised across providers, and validated through long-term studies that link changes in biological age to specific behaviours.

So while one-off tests of biological age make for impressive social media posts, for most people they represent a significant cost and offer limited real value.

The good news is we already know what we need to do to increase our chances of living longer and healthier lives. These include:

• improving our diet
• increasing physical activity
• getting enough sleep
• quitting smoking
• reducing stress
• prioritising social connection.

We don’t need to know our biological age in order to implement changes in our lives right now to improve our health.

Hassan Vally, Associate Professor, Epidemiology, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.