There is No Such Thing as Aging
Today's open access commentary is intended to provoke discussion on the topic of how aging is thought about and presented, particularly at the intersection between the scientific community and the rest of the world, or between scientific disciplines, or between scientists and funding institutions. It is an interesting read, as such commentaries often are.
Aging, of course, exists. It is a useful word that is applied as a bucket to hold a very complicated, ever-changing, and still comparatively poorly defined set of degenerative processes and the consequences of those processes. We age, we decline. That much is evident and right in front of our eyes. So a term will be invented and applied to it; we humans are nothing if not ruthless taxonomists.
In another sense, however, there is no such thing as aging. Aging is a fiction, like all abstractions, and it is frequently counterproductive to try to deal with the bucket rather than the inconveniently complex contents of the bucket. Focusing on an abstraction will lead one astray and distance one from the reality of the situation. That may well have been fine and possibly even helpful in the past, but it could be harmful at a time in which it is becoming possible to address the mechanisms that make up aging, to slow and reverse the consequences of those mechanisms.
What if there's no such thing as "aging"?
Some years ago, it was argued that aging is not a biological phenomenon. The argument - that there are not necessarily common mechanisms underlying the major aging-related chronic diseases, such as cancer, but rather a suite of individual disease processes synchronized via natural selection - would surely find little favor today. Common mechanisms, including inflammaging, mitochondrial dysfunction, and cellular senescence, are now thought to be well established. In retrospect, the argument seems ignorant of aging mechanisms. Here, we argue that this apparently ignorant view is right, but for the wrong reasons: that our more detailed knowledge of aging mechanisms is increasingly showing that there is no unitary phenomenon usefully summarized with the word aging.
What is aging? This question, at the heart of our field, has received a great deal of attention, and many definitions, implicit or explicit, have been proposed. (Here, we use the term "aging," though all our arguments equally apply to the term "senescence," which is favored by some). A coherent definition is even essential for the field: there are intensive efforts to measure aging, to slow aging, and to treat aging, and it will be impossible to know if they are succeeding without a clear definition of the subject of our research. Is it accumulation of molecular damage? Is it loss of function with increasing age? Is it increases in mortality (or decreases in reproductive rate) with age? Underlying the discussion to date is an assumption so basic it goes unnoticed: that there is an underlying biological phenomenon of aging.
We have a word for aging, and therefore we assume that science will accommodate us, providing a phenomenon to match our word. And in a colloquial sense this is certainly the case: no one can doubt that we see ourselves, our relatives, and our friends age. But is this colloquial usage scientifically justified? Is there really a "thing" or a phenomenon we can call aging? We argue here that our understanding of the biology is now sufficient to say definitively that this is not the case, that from a scientific perspective there is no such thing as aging, but rather a collection of disparate phenomena and mechanisms - sometimes interacting with each other - that relate in one way or another to our colloquial sense of the word. Accordingly, our desire to find a single reality of aging has created a great deal of confusion in the field.
We are well aware that not all researchers in our field will like our thesis here: our identity as "aging researchers" is tightly wrapped around the notion that there is a phenomenon of aging. However, we do not believe there is a need to feel any existential threat from this idea, which is in some sense a natural extension of the multi-factorial hallmarks of aging or pillars of aging framework. Rather, we think that being more careful about our underlying assumptions, and how they do or do not conform to biological reality, can only make us better researchers. The field of aging research can still exist, but with a more nuanced understanding that we are not studying a single biological phenomenon, but an assortment of loosely related processes that we find convenient to lump together.
Tell that to my aching joints, foggy brain, fatty rolls, tiredness, blurry vision, hearing loss, lack of stamina, depression, etc., etc....
I will say that for sure there's no such thing as **healthy** aging. There might be graceful and slowed-down aging, but I cannot call this process healthy by any stretch of imagination. There are a few life changes that are "normal". Growing pains, hormone shocks at adolescence, the profound changes during pregnancy and we culturally lump those with aging.
Something to add. Aging is not only a process of wear and tear, even though there is a good portion of it. It is also the tissues and organs just falling apart because they fail to maintain themselves correctly. This might look like a programmed death or rather is a series of failures or the upkeep systems that manifest as all the diseases we see in an aged body. This might be called an age-associated degenerative syndrome and be treated as a disease like metabolic syndrome, diabetes and others. There might be a treatment that stops the syndrome or a treatment to reverse the ongoing damage. The second approach might deal with any kind of root cause, but might require tissue engineering, organ transplants and possibly functional repair nanorobots. We still might be lucky and find a way to stop the tissue aging without mastering the repair first. Probably by a few pathways like boosting autophagy and senolitics. i
If the tissues remained "young" we would still accumulate other types of damage which the regeneration cannot repair like scarring, and other damage due to wounds and accidents. We would still need to repair all the damaged parts but the urgency would be greatly reduced. And probably the maximum life span can easily go to a few hundred years due to Gompez law being replaced with a normal distribution
My guess is that we (as the humanity as whole, I might not make it) will first tweak a few root causes which would cause the increase of the healthspan and a minor increase of max span and then at some point , all the organ an tissue printing and in-vivo repairs will catch up.
If there is no such thing as aging, then we should be able to define all of the effects of aging in terms of their underlying molecular biology and then got on with developing effective solutions for these problems.
Probably, to these researchers there is no such thing as the human body but rather a collection of disparate molecules and chemical reactions - sometimes interacting with each other - that relate in one way or another to our colloquial sense of the word.
It's a complex matter, but just a comment: "aging" is a word used not only for biology, but for non-living things as well, like a chair, a freezer, a computer or a car. So, to analyze "if 'aging' scientifically exists" it's necessary to look at the word from this broader point of view.
For a very broad definition, take a look at http://dx.doi.org/10.14336/AD.2018.1030, at least for living things:)
@Nicolas Chernavsky.
You are correct. Most complex things are aging living and non-living.
A short definition of aging is: increasing disorder with a passage of time. (Is there such thing as time? Some deny existence of objective time. Perhaps there is only Motion - increasingly disordered Motions of molecules- is another definition of aging.)
Of course there are disorders that are not age related. So aging is the most generalized Disorder which is increasing with passage of time (or with increasing number of Motions of Earth around the Sun [colloquially called years])
So a cure for aging is restoration of the most generalized order of biological molecules, cells, tissues , organs and the entire systems of organs - the organism. -- It is a cure of biological aging.
But there is also mental aging. If any human lives for a very long time- hundreds or thousands of years, there will be accumulation of memories, reaching the storage capacity of a brain 🧠., -. one will not be able to form any new memories ( at least long term memories) - will become mentally old while appearing biologically young-looking .
So to cure mental aging there must be a method developed to erase selectively some memories to make brain space for new memories. After living for thousands of years most humans would want to be mentally rejuvenated.
In 1956, Denahm Harman described his theory of aging. If you read it, it would not occur to you to philosophize in this way and you would prolong your life two to three times.
Everything in the world is aging. Dead organisms age faster than living ones. This means that organisms actively prevent oxygen poisoning. I don't see anything mysterious or incomprehensible in that. Aging occurs when irreparable DNA breaks occur. That says it all. I wonder if anyone could figure out how to join those broken DNAs. This is not out of the question, because evolution takes place without intelligence.
There is still the problem of why antioxidants do not work. This problem was solved in 1961. Antioxidants work for me. So I just "smirk" and "rejuvenate" every 10 years for 5 years.
I liked the paper because it let me think critically but I stand with Reason's remarks. What I particularly liked is the remarkable similarity of Fig 1 to neural networks (NNs), maybe not a coincidence that Deep NNs are currently used aggressively in aging research. Note from the lines (vs dotted) how calorie intake, exercise and microbiota are well documented to link to the central known aging pathways.