chronological vs biological age: the art of ageing

chronological vs biological age: the art of ageing

For most of us, there comes a time when our body starts to feel like it could fall apart at any second. Our memory shames us and at our lowest point, our weekly trip to the pharmacist is the only exercise we’ll be having. It’s a fact that ageing is inevitable. 

But what if it isn’t?

Do you know how old you are?

Forget about the number of years you’ve been on this earth, lately scientists are starting to classify a person’s true age based on how well they are in mind and body, rather than how long they’re walking on this planet. The best thing about that? We actually have a lot more control over our own ageing process than we think.

Dr. Morgan Levine, professor at Yale University and one of the leading experts on the biology of ageing, says we have two ages. Everyone has a chronological age. This is the time that has passed from your birth to the given date. It’s the time you have been alive in terms of exact years, months, days and even seconds. Many gerontologists however, believe chronological age to be an incomplete figure because it doesn't take all factors into consideration. 

That’s where your biological age comes in, also known as your physiological age. This is the age of your body itself and depends on a bunch of factors, both controllable and uncontrollable, that differ from person to person. It can be best described as the state of decline that your body has undergone during a specific period of time. These two ages are not necessarily the same. So, do you know how old you really are?

Your healthspan is not your lifespan

A lot of time, money and attention has been spent on the possibility of extending one's lifespan. But is this the right way to go about this? Our lifespan is the amount of time you’re going to be alive. More important than this is what scientists describe as your healthspan: the amount of time in your life without suffering from any disease and any form of physical and mental decline due to ageing.

When we are talking about slowing down the ageing process, we’re actually trying to extend a person’s health span. Of course, we need to keep researching possibilities of a longer life, but we want people living longer in the healthiest state possible for as long as possible. In this respect, we do not speak of anti-ageing but rather of healthy ageing.

The hallmarks of ageing

Fatigue, wrinkling, forgetfulness, hair loss, bad hearing, groaning when getting up and playing bingo. These are only a few of the symptoms of ageing; the question is what causes it?

Throughout the years, scientists have been able to establish a certain number of “hallmarks of ageing”. These are molecular and cellular changes that appear to change with ageing or can even impact the process altogether.

Cellular senescence

While we are ageing, a lot of our cells change their states and transform into different kinds of cells. One of those is senescence. In this state, cells lose the ability to multiply or copy themselves due to stress factors. They are no longer able to generate new cells, but can’t die either. This effectively makes them zombie cells.

The accumulation of these cells in the body has been a matter of debate for some time. Many see this as a driving factor for ageing and the associated ailments. When more and more senescent cells accumulate in the body, inflammations, tissue damage and cancerous cells become more frequent. People believe that a vast presence of these cells is the main driver of ageing and age-related conditions.


Telomere length is another aspect that scientists consider to be a marker of biological age. These telomeres are the nucleotides, repeating segments of non-coded DNA, that live at the ends of chromosomes. They are essential in keeping chromosomes from deteriorating and fusing with others. Simply put: they determine how fast cells age and die.

Telomeres shorten with every cell division. When they are so short that they cannot continue to divide, the cells will wither and die. Scientists have discovered that the shorter a person’s telomeres, the higher the risk for developing a disease or even for an early death. Recent studies have shown that telomeres can actually be restored and lengthened by maintaining a healthy and balanced lifestyle. Again, this leads us to believe that ageing is in fact a dynamic process that can be slowed down and even that how you live can impact your DNA.

Mitochondrial dysfunction 

For everyone who’s ever had biology in school, this sentence might sound familiar: the mitochondria are the powerhouses of our cellsThey provide the necessary energy for the functioning of our cells and produce 90% of our cellular energy. Besides this, they also play a key role in the synthesis of amino acids and lipids, and regulate recycling processes in our cells via processes called autophagy and apoptosis. 

Ageing has been linked to a decline in mitochondrial functioning. When this happens, it may result in malfunctions of our cells. To put it simply, our energy supplies go down and the health of our cells declines. This translates into a decline of our metabolism, our energy levels and muscle functioning. The right diet choices, sufficient exercise and stress reduction may help keep the activity of the mitochondria in place.

Find out your true, biological age

The big question remains: how old am I really? Studying the hallmarks of ageing has made it possible to develop comprehensive methods for discovering what your biological age is. To do this, we can rely on two types of data.

First of all there’s the clinical data you get by visiting your local doctor. We don’t mean the diagnosis you get when you have to cough a few times, and your doctor takes a look at your throat. We mean the results of your yearly physical examination - and you really should do this yearly - in which they measure your cholesterol levels, sugar and salt intake and much more. You can easily input these numbers in one of the many calculators you can find online. These tools can give you a broad estimate of your biological age, without taking into account strictly personal characteristics.

Another way is the study of biological markers. At Zirtui for example, we study your epigenetic profile. For ages, we believed that DNA was invariable. “Epigenetics” refers to the fact that while your lifestyle choices won’t modify the key structure of your DNA, they do have the ability to modify the way your DNA works. Your genes may contain certain flags (so-called DNA methylation) on specific locations that influence the performance and expression of your DNA. This activity can turn off or repress certain parts of the human genome, while activating others. Based on this activity, we can measure biological age by measuring the amount of chemical modifications at very specific spots in your DNA. 

By analyzing your saliva in our specialized laboratory and putting the results through an ingenious algorithm, we can evaluate your epigenetic profile and determine your biological age. After a few weeks you’ll get the full results saying: “Here’s your biological age, and this is how you can improve on it!”

Your genes load the gun, but lifestyle pulls the trigger

Now we finally know how we age, and what our actual biological age is, how do we reverse the process? Simply put: you can’t. There’s no way of reversing the ageing process, in a kind of Benjamin Button sort of way. Nobody has invented a genetic time machine that can instantly make us feel and look 20 years younger again (as far as we know).

But if epigenetics has proven us anything, it’s that we’re not destined to live out the same healthspan as our ancestors. While certain diseases and health properties are coded into our genetics, it’s how you handle stress, how you exercise, how much sleep you get, which medications you take, and what you eat that determine if those genes are being activated. There are even a few places in the world that can testify to this, the so-called blue zonesChanging our routines and making positive changes can actually lead to a healthy ageing process. Your DNA is not your destiny. Or as we like to put it: genes only load the gun, but your lifestyle pulls the trigger!

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