The Differential Calculus of Aging

October 2022

By Richard Fleming

Scientists are gradually unravelling the mysterious biology of human aging. DNA becomes damaged. Cells lose their ability to replicate and repair themselves. Telomeres, the regions at the ends of chromosomes, shorten. But a confounding aspect of the aging process is that different organs and body parts grow old asynchronously. Some age more rapidly. Others more slowly. For each person, the differential aging speed of body parts varies.

According to my birth certificate, I am 71 years old. But I am made up of various components. Each regularly communicates with my brain. Some proclaim their youthful vigor and demand gratitude. Others ask for accommodations because they are older. Juggling these competing claims can be challenging.

Two of the oldest parts of my body are my ears. For all intents and purposes they are pushing 87 years old. They disdain and dismiss the rich world of sound encircling me. And they try to distract me with a constant hissing noise. They insist I lower my expectations for auditory enrichment and demand I provide them hearing enhancement devices.

My eyes, myopic and with increasing floaters, celebrated their 75^th birthday when my birth certificate said I was in my 50s. But thankfully, and for no apparent reason, the premature aging slowed. Their performance level stabilized, neither improving nor diminishing further. They now appear to be biding their time until the rest of my body catches up. What my eyes will choose to do when I officially turn 75 is anyone’s guess.

My right first toe is far older than its nine compatriots, thanks to a 50 pound marble table slab doing a header on that toe many years ago. (Please don’t try to replicate this maneuver at home.) A broken bone and damaged nail bed will definitely accelerate the aging process. For the most part, the other nine toes tolerate the older digit. But some days their patience wears thin, at which point I have no option but to sit down.

On the other side of the ledger, my mouth and tongue remain quite youthful. They relish good food and drink as much now as many decades ago. Truth be told, I sometimes wish they would age a bit more quickly. But they are living life on their own schedule and their enthusiasm requires I spend more time on the elliptical in the garage.

Some organs are reticent about proclaiming their age. My heart, for example, has diligently performed its duties for 71 years with no significant protestations or announcements. My best guess is that it is about 55 years old. But who knows? Tomorrow it may divulge its age is 80. I’ve never been one to object when people or body parts are bashful about revealing their true age. I prefer to let sleeping dogs lie rather than wondering who let them out.

I could offer an inventory of other body components, but doing so would quickly devolve into the swamp of TMI. Suffice it to say my birth certificate does not accurately capture the differential calculus of my aging body.

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One arena of variability in bodily aging holds greater importance. It first came to my attention when I was in practice. My older patients often reported their surprise when they looked in the morning mirror. In their brain they felt they were 30 or 40 years old. But the mirror told them they were 70 or 80.

In my early years of practice, I sympathized with these patients. I blithely reassured them this disconnect between mind and body was common to aging. Sympathy was easy to express when my personal experience with the mind-body discrepancy was limited. But as my years in practice accumulated and I traveled further down the road, my approach began to change. I stopped sympathizing with my older patients and began empathizing with them. Empathy more accurately expressed my resonance with my fellow travelers.

Sympathy can be hollow, pro-forma. Empathy is genuine, heartfelt. When it comes to understanding aging, sympathy and empathy are separated by the date engraved on our birth certificate.

In an ideal world, perhaps human aging would be better coordinated. Each organ would grow old in synchrony and harmony with every other. But, as reality clarifies for us on a daily basis, we live in a less-than-ideal world.

If I could choose one organ to age more slowly, it would of course be my brain. I would like to preserve my ability to converse with my grandchildren in a stimulating way for years to come. I would like to listen to great music in the 2040s, wearing hearing aids of course. I want to be able to read poetry, even when my knees will no longer let me stand.

But there are downsides to a 40 year old brain inhabiting a 90 year old body. The brain’s understanding of what lies ahead grows increasingly bittersweet and profound. While opportunities for living remain, the frame of time is visibly shrinking. Some potential persists, but much potential is lost.

As we trudge forward, our powers of clairvoyance improve. We gain the ability to predict our future. We come to know that full synchronization between our brain and our various body parts lies ahead. When that time comes, our birth certificates will gain precision. And the differential calculus of growing old will confound us no more.

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