What Is Biological Age?

How Is It Different Than Your Normal Age, and Why Is It Important?

Akshaj Darbar


Everyone knows that as a person gets older, their health slowly gets worse and worse. From a young age, we’ve seen grandparents and other “old” people suffer from different diseases, frailty, poor eyesight, and a host of other problems.

But what some people might not realize is that it’s not as simple as a linear function where everyone in the world has the same health deterioration at the same age. There are people in their 30s who can barely lift heavy objects and might be taking loads of medications for a host of conditions, but, at the same time, there are also athletes in their 80s pushing their bodies for better performance.

Yūichirō Miura, at the age of 80, became the oldest person to summit Mount Everest | Photo on considerable.

Obviously, you might wonder, why is it that some people age faster than others?
The reasons behind this are plentiful, and more are continuously found by medical researchers, but in general, it is a combination of genetics (if you were born with traits that play a positive or negative role on your health) and your environment (what you eat, where you live, how stressed you are, etc.). Because of all these variables, it’s difficult to truly assess and predict your health conditions simply by knowing how old you are. For this reason, scientists have defined two different types of age: chronological, and biological.

What’s The Difference?

Chronological age is the age you’re familiar with: how much time it has been since you were born. I, at the time of writing this, am 18 as of recently. But, health-wise, I’m not exactly like all other 18-year-olds. I know some 18-year olds that are much healthier than I am, while others are suffering from worse health.

Every year, on your birthday, you celebrate an increase in your chronological age, but your biological age doesn’t change as periodically | Photo by Brooke Lark on Unsplash

In contrast, biological age is a representation of your health conditions and a predictor of how soon a person will exhibit chronic conditions of late-life.
These conditions include heart disease, osteoporosis, diabetes, and others commonly associated with old age. The only difference is that, whereas the correlation between the development of these diseases and chronological age is highly variable from person to person and lifestyle to lifestyle, their correlation with biological age is quite strong.

To develop an accurate prediction of your biological age, researchers and doctors have to observe a variety of different biomarkers that serve as proxies for biological age. These include physiological markers like bone density, blood pressure, and many others that doctors test for routinely. But, these physiological biomarkers are often symptoms of the chronic conditions of late-life, rather than predictors.
For example, by the time doctors pick up on low bone density, likely, you’ve already started experiencing pain in your bones or joints, and it’s probably already too late to improve the condition substantially.

But, newer research into many of these conditions has revealed cellular biomarkers of many of these conditions, changes in which can be seen years or even decades before any of the conditions really start developing.

The Epigenetic Clock

One such biomarker is the level of DNA methylation. DNA (deoxyribonucleic acid) is the molecule found inside all your cells that holds the instructions to make various proteins, which then carry out functions around your cells. Your cell’s entire DNA, called your genome, is split up into sections called genes, and each of these genes codes for one specific protein.
But this DNA is the same across your entire body, even though you have so many different types of cells. To make sure that only the proteins important for a specific type of cell are made in those cells, your DNA (or genome) is controlled by a system known as the epigenome. This epigenome controls which genes can actually be read by your cell so that only the proteins coding for those genes are produced.

One way it does this is by a process called DNA methylation, where it adds methyl (carbon atom with three hydrogen atoms) tags to your DNA, or proteins associated with your DNA, at specific loci, which blocks your cell from being able to read the genes at that spot.

This figure shows methyl groups being added to proteins called histones, which then tightly coil the DNA so that the genes can’t be accessed. Methyl tags can also be added directly to the DNA molecule to make it inaccessible (not shown in the figure) | Figure by Lumen Learning

Interestingly, researchers like Dr. David Sinclair and Dr. Steven Horvath noticed that as people got older, their DNA started to accumulate more and more of these methyl tags, for reasons still not completely known to us. So, Horvath took some tissue samples from people at various ages and analyzed their DNA methylation levels, and was able to develop an epigenetic clock that could accurately determine your biological age based on the level of methylation in your DNA.

For example, if I’m currently 18 and get a biological age of 35, then it means that my body’s methylation, and likely several other biomarkers, is similar to that of an average 35-year old, indicating that I’m severely unhealthy for my age, and will likely develop chronic conditions of late-life much sooner if I continue living life the way I am. If instead, I get a biological age of 18, or lower, then it means that my body’s health is similar to, or better than, the average 18-year old, meaning that I’m likely living a healthy life and will probably develop chronic health conditions much later.

Implications of Knowing Your Biological Age

So, why exactly is knowing about your biological age important? Knowing your biological age can help you make changes to live a healthier life and delay, or even prevent, various chronic conditions of late-life. This falls into an area of medicine called personalized medicine, which focuses on the individual differences in people when treating them for disorders or prescribing a way of life to avoid diseases, instead of giving the same treatment to everyone regardless of their differences.

With some of the tests that can be used for biological age, researchers can also extract information about other factors that might be influencing someone’s health and develop informed prescriptions for how a patient should be living their lives, like the kind of activities someone should or shouldn’t be partaking in, or foods that might be beneficial or damaging to one’s health. With these prescriptions, patients can completely change their health and delay or even prevent, many of the chronic health conditions that develop with age.

At Biotein, our goal is to create a better bio-age test that detects proteins associated with cell senescence, one cellular biomarker associated with biological age, in order to equip people with the power to truly take control of their health. We hope to use our test to offer personalized suggestions, taking into account factors like gender, race, and other demographic factors that are often overlooked by other companies but still play a large role in a person’s health. The test is still under development, but more details about the test can be found on our website (linked at the end of the article), which also has a sign-up link for our newsletter if you would like to stay updated with our progress and work.

Right now, these technologies are still relatively new, and researchers can only extract some information about optimal lifestyle options, but as the technology develops and researchers learn more and more about biological age and proxies that can be used for analyzing it, the day where you can take a quick test, mail it off to a lab, and then receive a personalized portfolio with everything you should and shouldn't be doing to completely optimize your life for longevity and health isn’t far away.

Key Takeaways

  1. There are two types of age: chronological and biological age.
  2. Biological age is a predictor of how soon someone will begin to develop chronic conditions of late-life.
  3. One way to determine biological age uses an epigenetic clock, which tracks the DNA methylation levels in your body.
  4. Knowing and understanding your biological age can help you with personalized suggestions to live a healthy lifestyle.

On A Personal Note

Thank you for taking the time to read this article. If you liked it, please clap for the article so that more people can see it.

To stay updated with more of my articles (about different areas of technology and medicine, including lots of neuroscientific research), follow this Medium account, check out my personal website, and follow me on my LinkedIn and Twitter accounts to keep up with my progress.

Also, check out the Biotein website to find out more about our mission, projects, and science!

That’s all for me. See you next article!



Akshaj Darbar
Writer for

MD Candidate at McMaster University. Researching blood cancer detection. www.akshajdarbar.com