How Old Are You Really? (And Why It Matters More Than You Think)
Your chronological age is just a number. Your biological age could be telling an entirely different story. This is Part 1 of a 3-part series on biological aging.
This year marks my 20th high school reunion, which is both humorous and humbling. Reunions are great for reconnecting with lost friends and chatting about old times, but let’s be honest, we’re all secretly scanning the room to see how everyone is holding up. I imagine that some classmates will look like they haven’t aged a day since senior year, and others will look like they have lived several lifetimes. Reunions are a strange, fascinating mirror into time, and a reminder that aging isn’t one-size-fits-all.
Aging is inevitable though. You’re aging right now. In fact, you’ve been aging since you were conceived, or maybe even before that, since some scientists think that certain exposures can be passed down generationally.
But how fast you age? That is more malleable. Why?
In recent years, scientists have drawn a sharper distinction between chronological age and biological age.
Your chronological age is how long you have lived. It is the number of candles on your birthday cake.
Your biological age is how old you are on the inside. It reflects aging at the cellular level, and it is based on accumulated cell damage over your lifetime.
Here’s the surprising part: these two ages don’t always match. You might be chronologically aged 40, but biologically you could be 50 or 30.
Why Biological Age Matters More Than You Think
Think of biological aging like wear-and-tear on a car. Two people might have the same make, model, and year, but one’s been skipping oil changes and driving aggressively off-road, while the other has stayed up to date with routine maintenance and repaired minor cosmetic damage. Over time, it shows, and it also impacts the car’s longevity.
It works the same with humans. Biological aging explains why two people of the exact same age can have vastly different health and aging appearances. That contrast of who will look older or younger at my high school reunion? That is biological aging in action.
As we get older, the difference in how we age becomes more pronounced. Take for example, two 70-year-olds. One might be running marathons, while the other is wheelchair bound. How is this possible? Because our biological clocks tick at different speeds. Some age faster and some age slower. For this reason, a person’s biological age is a better predictor of developing chronic disease, disability, and early death than their birthdate.
How Does Biological Aging Work?
Behind the scenes, your body is busy repairing DNA, managing inflammation, replacing cells, amongst other things. Over time, those systems slow down or break down entirely, and for some this happens more quickly than for others. Scientists have identified 12 hallmarks of aging, or parts of a common biological story that shape how we age and when disease shows up.
I won’t go into detail about each of the individual aging hallmarks, but they are an interesting cast of characters, all playing different roles in our aging story. You can group them into three connected categories: primary, antagonistic, and integrative hallmarks of aging.
Primary hallmarks are the original sources of damage that build up over time, like wear and tear on your genome, the shortening of telomeres (protective caps on chromosomes), or problems with how proteins and cell parts are maintained. These changes steadily pile up and are a clear driver of aging.
Antagonistic hallmarks are the body’s natural responses to that damage. They are like the hero who turns into a villain in the biological aging saga. Early in life, these responses help us grow and stay healthy. But as we get older, those same processes can speed up aging. For example, cellular senescence is a process that helps with wound healing and suppressing cancer development, but as we age and the body is unable to clear these cells, it can lead to chronic inflammation that can drive age-related disease.
Finally, when damage from the primary and antagonistic hallmarks builds up beyond what the body can handle, the integrative hallmarks kick in. These include things like chronic inflammation, poorer communication between cells and tissues, and a decline in the number and function of stems cells, leading to a loss of ability to repair and regenerate tissue. At this stage, the systems that once kept things in balance begin to break down, and the aging process accelerates.
In short:
· Primary hallmarks are the damage.
· Antagonistic hallmarks are the body’s effort to fight back.
· Integrative hallmarks are what happens when the damage wins.
Together, they form a cascade that explains not just how we age, but why our bodies eventually lose their ability to recover.
Why Does This Matter?
Medicine commonly focuses on treating one disease at a time: cancer, heart disease, dementia, etc. But researchers have noticed that all of these chronic diseases become more common as we get older. That led to a new idea – the geroscience hypothesis, which suggests that if we want to prevent these diseases, then we should start by targeting the biology of aging itself. That is, addressing the root cause that makes chronic disease more likely to begin with.
The good news is that there are things you can start doing today to slow down how fast you biologically age. This will help you look and feel better as you age, and it will help stave off chronic disease, disability, and potentially prolong your life. In part 3 of this series, I will talk more about these strategies.
Final Thoughts
Chronological age tells you how long you’ve lived.
Biological age gives you a better sense of how well you’re living.
Understanding this difference allows us to add both: years to our life and life to our years.
In my next post, I will walk you through how scientists measure biological age and how you can use some of these ideas to make sense of your own health and aging.
Want to know your “real” age? Subscribe and stay tuned.
For you reading pleasure:
Lopez-Otin et al., 2023, “Hallmarks of aging: An expanding universe”, Cell
Hodes et al., 2016, “Disease drivers of aging”, Ann NY Acad Sci
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