Dr Isabelle Meurgey and Dr Alain Butnaru
We all have an age stated on our identity card. But our muscles, heart or brain do not necessarily age at the same rate. Can this difference be measured and, above all, what is the purpose of doing so?
ONE AGE… OR RATHER SEVERAL
Chronological age is simple: it is the number of years that have passed since birth. Biological age is more subtle. It seeks to estimate how well the body is functioning by comparing different markers with those of people of the same age. Two people in their sixties may therefore share the same date of birth, but not the same blood pressure, muscle mass, respiratory capacity or metabolic reserve.
THE GOAL IS NOT TO BECOME YOUNGER ON PAPER, BUT TO REMAIN INDEPENDENT, STRONG AND HEALTHY FOR AS LONG AS POSSIBLE.
Yet there is no single biological age hidden within the body. The arteries may be well preserved while the muscles weaken; the brain may remain high-performing despite a less favourable metabolism. The result therefore depends on what is being measured: cardiovascular risk, inflammation, cognition, strength, body composition or molecular markers.
WHAT CAN IT BE USED FOR?
The aim is not to obtain a figure that is more flattering than one’s chronological age. It is to identify earlier the areas that are becoming more fragile and where action is still possible: physical activity, sleep, nutrition, smoking, blood pressure, blood glucose… Followed over time, these data can reveal a trajectory that is more useful than an isolated snapshot. But a “biological age of 58” in a 52-year-old person is neither a diagnosis nor a prediction of lifespan. It is a statistical estimate, dependent on the method and the population used as a reference. Two different tests can therefore produce two different results without either necessarily being wrong.
THE BODY ALREADY PROVIDES VERY CONCRETE
CLUES The most informative tests are sometimes the least spectacular. Grip strength, measured by squeezing a dynamometer, provides information about overall muscle strength. Walking speed reflects the muscles, balance, the nervous system and cardiorespiratory capacity. The Timed Up and Go test — standing up from a chair, walking three metres, turning around and sitting down again — assesses mobility. The number of chair stands, balance on one leg, respiratory capacity or VO2 max complete this picture. These measurements do not always provide an age in years, but they are directly linked to what matters: remaining mobile, avoiding falls, maintaining independence and tolerating physical exertion. They also make it possible to set simple goals and monitor progress.
WHAT ABOUT EPIGENETIC CLOCKS?
These tests analyse DNA methylation, small chemical marks that change with age, the environment and health. The first clocks, such as those developed by Horvath or Hannum, mainly sought to predict chronological age. Later generations, such as PhenoAge or GrimAge, reflect the risk of disease and mortality more closely. DunedinPACE goes further: it attempts to measure not only an age, but a pace of aging. Their sophistication should not obscure their limitations. The result varies according to the clock, the tissue analysed, the laboratory and the computational processing. An unfavourable score cannot predict a specific disease or an individual’s life expectancy. Nor does an improvement in a clock following an intervention yet prove that a person has actually become younger or gained years of life. Today, these tools remain primarily intended for research.
THE RIGHT APPROACH: LOOK AT THE TRAJECTORY
To age well, it is therefore better to avoid chasing a miracle number. The most useful assessment combines conventional risk factors (blood pressure, blood glucose, lipids, kidney function, smoking) with practical capabilities (strength, walking, balance, breathing and cognition). A molecular clock may potentially complement this picture, but it should not replace it. The real question is not: “What age does my body show today?” It is rather: “Which functions do I need to preserve, and in which direction are they changing?” Because the goal is not to become younger on paper, but to remain independent, strong and healthy for as long as possible.
Dr Isabelle Meurgey
Doctor of anti-aging and aesthetic medicine. Graduate of the Rouen medical faculty. Has specialised in preventative and performance medicine since 1997. Permanent member of the French Society of Aesthetic Medicine.
Dr Alain Butnaru
Graduate of the Paris Medical Faculty. Aesthetic and Anti-Aging Medicine since 1985. Permanent member of the French Society of Aesthetic Medicine. Degrees in Morphological and Anti-Aging Medicine.
