How Old Are You Really? Are the Latest 'Biological Age' Tests Reliable?

There is potential in the concept behind these tests, but there are limitations too.

- Hassan Vally

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?