My mind is consumed by the effort to provide a workable, terse definition of aging. Is it a disease? Is it a thing or a process? A noun or a verb? Does it deserve a chapter in our pathology text books? Can time kill you?
In a paper that I wrote several years ago, Redefining Human Aging, I invoked the image of a grandfather's clock. When it stops running is it broken? Fix it. Is it worn out? Junk it. Or does it need to be wound up? I favor, most commonly, the last choice. Most of what is usually attributed to aging, isn't. If it isn't then what is it?, and can we do anything about it? The Serenity Prayer needs to know what it is.
The World Health Organization is currently wrestling with this issue. Their International Classification of Diseases is the worldwide document that is used to classify diseases and related health issues such as mortality. It is about to release its updated formulation, ICD-11, next year. Their classification has uses beyond mere health issues as their imprimatur carries implications which carry financial valuations. If aging is considered a disease then like the bulk of the conditions on record is it not then a billable condition? Their recent nomenclature includes a category 2015 ICD-10-CM. Within this is Diagnosis Code R54. This includes "age related physical debility, frailty, old age, senescence, senile asthenia, senile debility, BUT it excludes senile psychosis from its list.
Despite my best effort to grasp any deep insight provided by the WHO their effort is fuzzy. Theoretically anyone over 65 would fall into this category, effectively removing any distinguishing features except "old". Following such a trend then there should be a category "alive", rendering the whole effort as silly.
My intuition is that their scheme is largely driven by the desire to generate a financial connection. Proclaiming a condition to be a disease conjures up a bill. The recent similar discussion about whether to label obesity as a disease was similarly fiscally motivated.
Data about the prevalence of aging are pretty straightforward, one per population member. In one sense aging is a worldwide epidemic everybody will catch it if they're lucky.
The recent report of Joanne Lynn published by the Hastings Institute helps to focus the issue.(1) In her listing of causes of death she cites first those that occur in the 60s often of cancer. Her second grouping of causes of death, usually in the 70s, involves a major organ dysfunction, heart, lungs, kidneys, liver as the causative agency. Joanne's third classification of deaths, occurring largely in those over 80 years of age are loosely grouped as system-wide failure, liability for failure. This category is the gorilla in the room and is destined to consign all prior categorizations to relative insignificance.What process underlies this pathology? Figures in the scientific literature about the prevalence of aging's partner, frailty, vary immensely, from 4 to 59% in one review. Varying linguistic features hamper a firm grasp of aging's mechanisms. With the surge of global aging any figures on prevalence are assuredly under estimates. Kirkwood goes so far as to suggest that since aging is so universal that it is actually built into the process of being alive. "Does life contain the seeds of its own destruction?" Demetrius further presents a perspective on Alzheimer's Disease that concludes that its appearance is coded into the process of life. In this view Alzheimer's Disease is intrinsic to the system as a whole.
Alex Carrel won a Nobel Prize for his demonstration that cells in a Petri dish appear immortal. He was wrong. His results were an artifact. Good friend Leonard Hayflick, hopefully still a Nobel candidate, cleared the air and observed instead what is generally called the Hayflick Limit. That is cells have only a finite number of divisions in their game plan. Immortality is an illusion that is not in Nature's scheme of things.
In my view. Aging is part of a physical field recently labeled the Metabolic Field (Schrodinger).(2) As such biologic aging is a sub-type of universal aging. Everything in the Universe ages, stars, canyons, Chevies. Aging is the generic effect of an energy flow on matter over time.
The pathogenesis of biologic aging ,in my view, is the composite result of the "molecular storm", a lingering remnant of the "Big Bang". (3)All of our submicroscopic particles are in constant motion, homeodynamics, that are constantly bumping into one another, an entropic friction that eventually wears us out in the process known as aging.
That doesn't sound like any disease that I am familiar with.
1) Lynn,J. Living Long in Fragile Health.. The New Demographics Shape End of Life Care 2005 Hastings Center Special Report S 14-S18.
2) Bortz W. Metabolic Field (Schrodinger) an Explanatory Platform for Biology 2015 Medical Hypotheses
3) Hoffmann P. Life's Ratchet.. How Molecular Machines Extract Order from Chaos 2012 Basic Books NY.