Biological age tests are becoming increasingly popular. Many produce a simple result: your body appears biologically younger or older than your chronological age.
But can one test really tell us our biological age?
The answer is more complicated than a single number showing the difference between your chronological and biological age.
Scientists have developed different types of aging clocks that use biological markers associated with aging. Some analyze changes in DNA methylation, while others use patterns in gene activity, proteins or metabolites.
These clocks do not all measure the same process.
A test based on DNA methylation captures different biological information from one based on proteins or metabolites. Research comparing different aging clocks has found that their results do not always closely agree.
But what does that number actually mean?
There is currently no single test that can measure the biological age of the entire body.
Different tests look at different signs of aging. Some analyze changes in DNA, while others examine proteins, metabolites or other biological markers. Because they measure different aspects of biology, two biological age tests may not give the same answer.
There is another important difference between aging clocks.
Some of the earliest aging clocks were designed mainly to predict chronological age. Newer models have increasingly been developed to capture information associated with health, physiological function, disease or mortality.
This means that two tests both described as measuring “biological age” may have been built for very different purposes.
It also means that a result showing that someone is biologically “younger” or “older” should not automatically be interpreted as a complete assessment of their health or future disease risk.
So being told that your biological age is “younger” than your actual age does not automatically mean that you are healthier or have a lower risk of disease.
At present, research has not established one universal test that definitively measures biological age.
The important question is therefore not only what number a biological age test produces, but what the test actually measures — and what that measurement has been shown to mean.
Biological age testing is still developing. Understanding what a test measures — and whether its results are linked to meaningful health outcomes — is more important than the number alone.
