A patient recently sat across from us holding a printout with a single number circled in red: “biological age, 41.” She was 52. She wanted to know if this meant she had, in some literal sense, borrowed eleven years back from time.

The honest answer is more interesting than yes or no—and understanding it is the difference between using these tests wisely and being quietly misled by them.

Two Clocks, Two Different Jobs

Every cell in your body carries the same DNA sequence, but not every gene in that sequence is switched on. The switches are chemical tags that undergo DNA methylation, largely at cytosine-guanine sites (CpG). These tags shift in predictable patterns across a lifetime.

In 2013, biostatistician Steve Horvath showed that measuring methylation at a defined set of CpG sites could estimate a person’s age from a blood or tissue sample with startling precision, often within a few years of their actual age.

That first generation of “epigenetic clocks” was built to predict chronological age. It succeeded, but it wasn’t yet telling us anything a calendar couldn’t.

The real clinical interest began with second-generation clocks like PhenoAge and GrimAge, which were trained not on birthdates but on health outcomes: mortality, disease onset and frailty.

These clocks ask a different question entirely: not “how old is this person?” but “how much wear has this person’s biology actually accumulated, regardless of what the calendar says?”

However, a more recent innovation, DunedinPACE, measures your current pace of ageing.

Why This Matters Clinically

The reason we take these tools seriously in a longevity practice is that population-level research has repeatedly tied epigenetic age acceleration to real outcomes.

According to a study published in 2025, people with faster DunedinPACE scores had measurably worse cardiometabolic profiles, such as higher BMI, higher glucose and less favourable blood pressure, while those with more physical activity and healthier behavioural patterns showed a slower pace of ageing.

Separately, it has been noted that accelerated epigenetic ageing is associated with an increased risk of stroke, and notably seen more strongly in people with first-time strokes than in those with recurrent strokes. This suggests that these clocks may be hinting at vulnerable blood vessels before it becomes clinically obvious through investigative modalities.

Another study has linked GrimAge acceleration to frailty in older adults, reinforcing that these markers reflect functional decline, not just statistical curiosity.

In other words, epigenetic age acceleration is a genuine signal of accumulated biological burden that sometimes moves ahead of the diseases it may be warning about.

What It Doesn’t Do

Here is where we ask our patients to slow down.

Epigenetic clocks were built and validated as population research tools. Using any single clock to make a confident, individual-level claim - “you are biologically 41”- stretches the science further than it was designed to go.

Firstly, different clocks frequently disagree with each other on the same person because they were trained to answer different questions.

Secondly, DNA methylation, the crux behind these epigenetic clocks, is dynamic and depends on various factors, such as recent illness, sleep deprivation or even the time of day a sample was drawn. A single snapshot can therefore reflect a temporary blip rather than a reliable long-term trend.

Thirdly, most direct-to-consumer kits now use saliva rather than the blood samples that were originally used, hence giving way to more variability.

And fourthly, there is still no universal, cross-laboratory gold standard for how these clocks are built or calibrated. This is why results can genuinely vary by years depending on which test and lab is used.

None of this makes the number meaningless.

It makes it a trend indicator, not a diagnosis—most useful when measured repeatedly over time, in the same lab, alongside a full clinical picture, rather than read as a single verdict on how well you’ve lived.

How We Actually Use It

At Dhun Wellness, we treat an epigenetic age result the way we’d treat any single biomarker.

We pair it with your metabolic panel, your inflammatory markers, your body composition and your own history, and we retest at intervals rather than reacting to any one draw.

Used this way, the clock becomes what it was designed to be: not a verdict on how old you “really” are, but a way to see, over months and years, whether the interventions we’re building together are actually changing your trajectory.