Missed “short & sweet” instalment no. 6 on “epigenetics”? Catch up here!
Could this become the next “Tinder” or “Parship” interaction:
“How old are you?”
“Well, I’m 45, chronologically, but my biological age is 33.”
Or is it way too futuristic?
Well, we might not be there yet, but a deep stare into epiAge’s crystal ball reveals that it may not be that far-fetched.
More seriously, the distinction between chronological and biological age is still relatively novel. But it has gained both scientific and mainstream traction over the last decade,because it points to a phenomenon, we are all intuitively aware of. Namely, the potential discrepancy between someone’s official age and the way they look and/or move in the world.
What is biological age then?
Unfortunately, you cannot define “biological age” without first defining its non-identical twin “chronological age”. So, let’s start with that, since it is pretty straightforward.
The Merriam-Webster Dictionary defines it as “the age of a person as measured from birth to a given date”. You could also define it as“the number of years (months, days…) that have passed since your birth”. So, a look into your passport or your birth certificate plus a little basic maths should quickly resolve any uncertainty...
“Biological age”, on the other hand, is much trickier to define. In fact, it can be found neither in the most authoritative English-language dictionaries – be they Oxford, Cambridge, Merriam-Webster, Chambers or Collins – nor in the Encyclopaedia Britannica, or even Wikipedia. And this even though the term was already introduced in medical literature in 1988 (Baker).
So, we will have to infer it from partial or tentative definitions provided by biomedical sources as well as the insights gleaned from previous “short and sweet” posts, not to mention anecdotal experiential evidence.
To start with the latter, your cardiologist, your beautician or your sports trainer may be indirectly referring to your biological age when they laud the youth of your heart or your skin, or when they criticise the inferior performance of your lungs compared to your age cohort.
Hence, “biological age” has something to do with the more or less youthful performance and/or appearance of your organs.
But as hinted at in previous short & sweet posts on “ageing” and the “hallmarks of ageing”, ageing is not limited to the relative age of our organs. Rather it refers to a broad range of transformations over time, taking place at different levels of your physiology and your metabolism – from your telomeres to your mitochondria, your microbiome and more.
These changes affect how your entire organism presents and how it functions, from the micro- to the macro-levels. Moreover, they are individually paced and do not necessarily evolve in a linear fashion.
This is why we like the following outlook: “[…] we define biological age as a latent conceptual value, reflecting the extent of aging-driven biological changes, such as molecular and cellular degradation.” (Bortz; 2023)
The fact that biological age is a “latent conceptual value” cannot be emphasised strongly enough. Indeed, it does not spring out as the outcome of a simple observation or measurement. Rather it is a somewhat artificial “construct”, woven from ageing clues strewn across the body.
Moreover, biological age is “often used to measure the progress of biological aging,[and] can indicate an aging individual’s life expectancy and health status.” (Bafei, 2023) This hints to the monitoring and predictive possibilities that biological age determination opens.
Biological age then potentially references the actual state of the body’s health and ageing from a whole organism perspective, compared to that of a cohort of individuals of the same sex and chronological age.
By now, you may be thinking “biological age makes sense and sounds really useful. But it does seem awfully challenging to measure, doesn’t it?”
And you might be on to something there since that is the topic of our next short & sweet episode: determining biological age. So, stay tuned!
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Sources & further reading
“chronological age”, Merriam Webster Dictionary. Online: https://www.merriam-webster.com/dictionary/chronological%20age
George T. Baker, Richard L. Sprott. "Biomarkers of aging". Experimental Gerontology, Volume23, Issues 4–5,1988, 223-239. doi:10.1016/0531-5565(88)90025-3. Online: https://www.sciencedirect.com/science/article/abs/pii/0531556588900253?via%3Dihub
Bafei SEC, Shen C. “Biomarkers selection and mathematical modeling in biological age estimation”. NPJ Aging. 2023 Jul 1;9(1):13. doi:10.1038/s41514-023-00110-8. Online: https://www.nature.com/articles/s41514-023-00110-8
Bortz, J., Guariglia, A., Klaric, L. et al. Biological age estimation using circulating blood biomarkers. Commun Biol 6, 1089 (2023). doi:10.1038/s42003-023-05456-z. Online: https://www.nature.com/articles/s42003-023-05456-z#citeas
Illustration
pixabay & epiAge
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