Biological age versus calendar age: what biological age tests measure, what the numbers are linked to and what a lifestyle scan shows

In this article you will read what your biological age is alongside your calendar age, how biological age tests measure it, what the numbers are linked to, what research says about bringing them down and what a lifestyle scan shows. That matters, because a number like this is an estimate from research and not a judgement about you: once you know how it comes about, you can read it calmly.

You know your calendar age to the day. The harder question is what your biological age is right now. Biological age tests, called “ageing clocks” (or “epigenetic clocks”) in the research, try to answer that question from a blood or saliva sample.⁠² The BioProfile lifestyle scan asks about your daily habits and gives you an indication of where you stand today, as one of the 11 health areas the full scan assesses. This is not a diagnosis. It is self-insight, to see where you stand today, and to help you make better choices in your nutrition and lifestyle. What this scan does not do: name a cause or a condition. That is work for a doctor.

Biological age versus calendar age

Your calendar age counts the years since your date of birth, at the same pace for everyone. An estimate of your biological age tries to describe how your body is doing. In a Swedish cohort of 845 adults aged 50 to 90, studied in nine measurement rounds from 1986 to 2014 with about 20 years of follow-up for mortality, eight of the nine measures of biological age (all except telomere length) predicted mortality independently of calendar age.⁠¹

For you this means that your date of birth does not tell you everything. People of the same age can be in a different biological state, and in groups that difference goes together with how long people live.

How your biological age is calculated

A systematic review gathered 33 biological age tests used in humans, called “ageing clocks” (or “epigenetic clocks”) in the research, with sample sizes of 53 to 62,419 people, in blood and saliva from cohorts of adults.⁠² Phenotypic tests combine routine measurements; epigenetic tests read chemical markings on the DNA. Second generation tests such as PhenoAge biological age and GrimAge showed a stronger link with death from any cause than first generation tests.⁠² So there is no official answer to the question what is my biological age: every answer names a test, a sample and a comparison group.

If you see a biological age given somewhere, look at which test was used and which group you were compared with, because a different test can give you a different number.

What a higher number is linked to

In the Dutch Rotterdam Study (n=1,347, median follow-up 8.6 years), a one standard deviation higher DNAm GrimAge was associated with a hazard ratio of 1.79 for all-cause mortality (95% CI 1.52 to 2.12), and the metabolite score MetaboHealth showed the same ratio of 1.79 per standard deviation in the same cohort (95% CI 1.52 to 2.09).⁠³ Among 1,942 participants in NHANES who were followed for a median of 208 months, every 1 unit increase in GrimAge acceleration was linked to a hazard ratio of 1.07 (95% CI 1.06 to 1.09).⁠⁴ This is not a personal prediction: these are averages across groups and years.

In plain words: in these groups, more people with a higher number died during the follow-up years than people of the same age with a lower number.

At what age do you age fastest

These sources do not name an age at which everyone ages fastest. What the sources measure is pace. DunedinPACE was developed in a birth cohort from 1972 and 1973 (N=1,037), out of 19 indicators of organ systems that were followed at the ages of 26, 32, 38 and 45.⁠⁵ Because that whole cohort was born in the same two years, the measure is about a difference in pace between people of the same calendar age. In a validation sample of 2,471 adults with an average age of 66, a standard deviation higher DunedinPACE was associated with a hazard ratio for death of 1.65 (95% CI 1.51 to 1.79).⁠⁵

For you this means that the pace counts and not just the number: two people of the same age can grow older biologically at a faster or a slower rate.

Can your biological age go down

One randomised pilot study gives the clearest number there is: 43 men aged 50 to 72 followed a nutrition and lifestyle programme for 8 weeks, and that group ended 3.23 years lower on DNAmAge than the control group (p=0.018).⁠⁶ One pilot, 43 participants, eight weeks, men only: that is not a promise but a signal.

The everyday version is better documented. The Dutch physical activity guideline for adults asks for at least 150 minutes of moderately intense activity a week spread over several days, for muscle and bone strengthening activities at least twice a week, and for not sitting for long stretches at a time.⁠⁷ In 2025, 48% of Dutch adults aged 18 to 64 met the whole guideline.⁠⁷ Thuisarts.nl sorts the advice on healthy living for adults into seven areas: eating and drinking, exercise, sleep, relaxation, social contact and meaning, alcohol, tobacco and drugs, and sticking with it.⁠⁸

What a lifestyle scan measures and what the scan does not measure

BioProfile’s lifestyle scan asks about your habits and gives you back a score with the reading band that score falls into. It is a questionnaire and not a biological age test: the tests above are read from blood and saliva samples in research cohorts.⁠² What you get is a starting value, and a second one if you repeat the scan later.

A questionnaire does not say what lies behind a low score. The scan is not a diagnosis. If a complaint is urgent, Thuisarts.nl points you straight to Emergency care: who do you call?⁠⁸ For complaints that persist or worry you, put the question to a doctor.

In summary

Your calendar age counts years, and your biological age is an estimate of how your body is doing that every biological age test calculates in its own way. In groups, a higher number goes together with a higher risk of death, but for one person it is not a prediction. That the number can go down has been seen in one small pilot study: a signal and not a promise. The lifestyle scan does not measure biological age, but it does show where your habits stand today.