In Search of a Useful Scientific Definition for "Aging"

What is aging? This deceptively simple question will garner you lengthy answers from the scientific community - many different lengthy answers, as it happens, some of which are even long enough to take the form of entire, complete books. There is a lot to be said on aging, and vast repositories of data, and yet there remain numerous different camps with different detailed definitions of aging - it's cause, its progression, and how best to build therapies that might slow or reverse aging.

So you have the definition put forward by Michael Rose and colleagues, or the hyperfunction theories that seem to be gaining ground among researchers of the small programmed aging camp, or the collection of mainstream views - many different interpretations and variants - that paint aging as a matter of accumulated damage.

And that is just on the matter of causes and mechanisms. The territory becomes much more of a jungle once you start down the path of asking whether aging is a disease, or whether it is a bad thing, or whether should be treated and ameliorated through medical science. Believe it or not there remain numerous researchers in the field who believe that aging should be studied but not treated, slowed, or reversed, despite the suffering and death it causes. Here is an open access opinion piece on this topic from Aubrey de Grey, via the Rejuvenation Research journal.

The desperate need for a biomedically useful definition of "aging" (PDF)

Surely everyone who studies the biology of aging fundamentally agrees on what it is they are studying, even if they may prefer somewhat different terminology to define it? I'm afraid you'd be wrong. Disagreement within the field about what aging really is and is not is very far from purely semantic, and the substance of those disagreements leads to profound differences of opinions concerning both what research gerontologists should prioritise and how they should communicate their work to others.

First: is aging a disease? Some gerontologists will just tell you "No, it is separate from age-related diseases". Some will say "No, but it is a risk factor for age-related diseases". Some will say "No, it is the set of precursors of the age-related diseases". Some will say "Yes, it is the set of precursors of the age-related diseases"! Self-evidently, whether X is a Y depends not only on the definition of X but also on the definition of Y, so one might excuse this chaos on the basis of a failure to agree on what is and is not a disease - and there is indeed no such agreement. But it gets worse.

Is aging a thing that is amenable, in principle, to medical intervention? Not if you believe the protestations of such eminent gerontologists as Bruce Carnes and Jay Olshansky, who in a recent paper critiquing (I employ classic British understatement in my choice of words here) various colleagues' work made, in spite of reviewers' efforts to educate them, the assertion that "What Wilmoth fails to acknowledge is that in order to reduce death rates at advanced ages to zero or close to it, our biology would need to be modified" (my emphasis). This sort of language, without stating explicitly that medicine can never maintain the body in a state of health so youthful that death rates will be vastly lower than today, unequivocally seeks to convey that view. So, do other gerontologists agree? Indeed they do not: if any evidence were needed, I may merely cite the fact that almost every mainstream conference on the biology of aging these days has a subtitle referring to delaying or even reversing aging.

Finally, is aging even a bad thing? At least here we find broad consensus among biogerontologists - those who study the biology of aging (though there are a few exceptions). But the same does not apply to all gerontologists: those whose field is more on the clinical, or the sociological, side tend to be among the most viciously and vocally opposed to any talk (let alone action) concerning actually doing anything about aging. As an example, a very senior (and, I am afraid to say, highly influential) clinical gerontologist from Canada recently wrote to me as follows: "I do not wish in any way shape or form to have my name associated with anti-aging medicine, regenerative or restorative medicine or some such". No kidding. I will be interested to discover, at some point, whether she is willing to defend that view publicly.

It should by now be apparent that there is a bit of a problem. Let me emphasise, however, just how much of a problem. At present, translational biogerontology (alternatively, biomedical gerontology) commands an absolutely minuscule proportion of the medical research budget of any industrialised nation. Why? Simply because the idea that postponing aging is a feasible and valuable goal, both socially and economically, has failed - despite the best efforts of many biogerontologists over many decades - to gain any significant traction among funding bodies.

I contend that gerontologists' muddled thinking outlined above concerning what aging really is is actually the number one reason for this failure.

Comments

Aging is like porn. You know it when you see it.

Posted by: Abelard Lindsey at March 21st, 2013 9:37 PM

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