Aging: Disease or Not? A Simple Guide
A guide to thinking through the medicalization of aging
Should we view aging as a disease to be treated? The following brief guide will help you navigate this question.
What is “Aging”
“Aging” is the set of changes our bodies undergo over time.
Colloquially, we refer to early changes, say from infancy to early adulthood, as “maturation” or “development.” We reserve the term “aging” for changes that happen thereafter.
Early changes we consider good: denser, longer bones, larger muscles, and so on. The latter changes we’re not so fond of: thinning, weakening bones, wispy hair, among others. More technically, we refer to aging as senescence.
Peak Physiology
So, when does maturation end and senescence begin?
The short answer is somewhere between our mid twenties to early thirties.
The long answer is more interesting.
Our bodies are made up of several organ systems that each develop at their own pace. The nervous system seems to mature in our mid-twenties, for example, while the skeletal system peaks a decade later. We can measure various “Key Performance Indicators” for these systems and plot them over time.
By tracking such indicators, it’s possible to trace the rise and fall of the body as a whole. We can then estimate the average age we reach our Peak Physiology. The steps are as follows:
Divide the body into its various systems
Pick one or more KPI for each system
Measure these KPIs across ages
Standardize and plot these measure
Average measures to get a whole body curve
A schematic might look like this:
This is an oversimplification:
There’s no reason the rise and fall should be quadratic rather than any other polynomial.
Organ systems are a contrivance. They’re an invention to help break down a complex system (the human body) into more palatable parts. Analysis at this level is only a practical choice. Aging occurs and is heterogenous at all levels: the individual, the organ system, the organ, the tissue, the cell, the subcellular organelle, and even the molecule.
Selecting the right metric isn’t always obvious. For instance, children’s bones may be less dense but their pliability can be an advantage.
But the point remains that various bits and bobs of the body mature and age at different rates and the parabolic curve is a reasonable first approximation.
Peak Physiology is when maturation ends and senescence begins
Post-Peak Pathology
Any net change after Peak Physiology cannot be advantageous. If it were, the peak would not yet have been reached.
The natural end point of the changes described above (again, that’s aging) are disease and death.
We can take the skeletal system as an example.
Our bone density increases until we’re about 30. Thereafter, it plateaus briefly then begins to slowly decline. If we live long enough, our bones will continue to thin until we develop Osteopenia and then Osteoporosis. These diseases put us at risk of fracture even in the absence of trauma. They can be painful, debilitating, and deadly.
There are countless other examples.
Fats are an essential part of our diet but their consumption leads quite naturally to disease.
A fraction of these fats are deposited in the walls of arteries. Some time in our teens we begin forming Fatty Streaks. Farther along these streaks grow and harden giving us Atherosclerosis. Hard vessels are less pliable and transmit more pressure as blood flows leading to Hypertension. As yet more fat builds up, vessels narrow, blood flow falters, and we get Coronary Artery Disease, Peripheral Vascular Disease, and other diagnoses. If the narrowing continues, vessels are blocked entirely or, more likely, bits of fat rupture leading to Myocardial Infarction (“Heart Attack”), Cerebrovascular Accident (“Stroke”), and many others.
I think you get the picture.
This chain of events is perfectly natural. A poor diet might accelerate it but even the healthiest diet can’t prevent it indefinitely. Given enough time it will happen to us all.
Ordinary, even essential, processes will lead to disease and death. After Peak Physiology, the mere passage of time is pathological.
This is why “Age” is a risk factor in so much disease. Chronological age is almost a direct statistical proxy to the progress of senescence.
Pre-Disease
The distinction between a disease and its precursors is often fuzzy.
This is at the root of some objections to calling aging a disease. Critics may say for example, “slightly thinner bones are not a disease.” These critics believe a condition must be symptomatic before it can be pathologized.
This is not how medical science works.
Most of the diagnoses mentioned above are asymptomatic. Osteopenia, Hyperlipidemia, Hypertension, Atherosclerosis, and others are all asymptomatic. But they’re so tightly linked to morbidity and mortality that they’re considered diseases in their own right.
Think of these as on-ramps. Since the ultimate destination is dangerous, the on-ramps themselves are considered dangerous.
. In fact, we go further. These on-ramps have their own on-ramps. Before Diabetes there’s Prediabetes and before Hypertension there’s Prehypertension. In fact, there’s also Hypertension Grade I, II, and III. All of them asymptomatic. There’s no tradition of reserving the term “disease” solely for symptomatic illness.
Aging begins as a collection of silent, pre-disease diseases and gradually morphs into good old fashioned, symptomatic, and fatal disease.
What about the environment?
To some extent, these dynamics are subject to environmental influence.
I still advise patients, particularly older women, to supplement with calcium and vitamin D and to weight train to protect their bones. But these behaviors act on a foundation that is inexorably deteriorating.
A 90 year old, no matter how much calcium she swallows or how many dumbbells she curls, cannot regain the bone density of her 20’s.
There is a finite limit beyond which conventional lifestyle choices cannot save us. The environment matters but only to a quite finite extent.
Summary
Aging is what happens after we peak physiologically. We can estimate when the Physiologic Peak occurs by tracking the rise and fall of our body’s functional metrics. A ballpark estimate is somewhere between our mid-twenties to early thirties. The environment plays a role but it’s limited. The natural end point of aging is disease and death. In medicine, we view the direct antecedents of disease as diseases in their own right. Aging is a constellation of antecedent diseases that are ultimately fatal. Viewed this way, we’ve been treating aging as a disease for millennia and rightly so.