Your typical rat lives for about two years. Slap a bushy tail on that rat, however, and the animal:
1) Suddenly becomes cute
2) Lives seven times longer
That’s right. Despite an uncanny resemblance to their nocturnal cousins, squirrels live seven to eight times longer than rats. We don’t know why this happens. Their genes are nearly identical.
Rodent genes are similar to ours too. Rats, for instance, share many genetic markers for disease with humans – making rats good research subjects. Since rats are so short-lived, we can run fifty generations of the little buggers in one human lifespan.
Yet at a deep level, we don’t know why a rat lives two years, a squirrel fifteen years, and a lucky human one hundred years. But we do know a healthy rat from an unhealthy rat. Unhealthy rats have more tissue damage, and this damage is caused by things like free radicals, aging mitochondria, and senescent cells.
“These fundamental processes are almost certainly driving tissue health,” says Dr. Judith Campisi of the Buck Institute for Research on Aging. “As for what actually drives lifespan? We really don’t know.”
So instead of lifespan, let’s focus on healthspan for the moment. Healthspan, according to Merriam Webster, “is the length of time that the person is healthy – not just alive.”
Here’s the basic idea: even if we can’t push human lifespan much past one hundred, we can still stay strong until our last breath.
Me? I want to climb a mountain when I’m 95. Perhaps it’ll look more like a grassy knoll than Everest, but what do you expect from a nonagenarian?
Here’s the interesting part. If I do manage to reach that age, there’s one marker that will predict my continued health, cognition, and capability. Any guesses?
Let’s rule out a few things first. The marker in question is not telomere length, liver function or glucose metabolism.
Give up? Fine, I’ll just say it. It’s inflammation.
What the hell is inflammation anyway?
The term “inflammation” gets thrown around a lot these days. I get the sense, however, that many people are confused about what it means. This is probably because I was confused about inflammation for most of my life. I can empathize with the mass confusion.
A quick refresher then. When we talk about inflammation in the context of aging, we are talking about chronic, low-grade inflammation. Chronic inflammation occurs when immune cells – inflammatory cytokines, for instance – infiltrate healthy tissue in the absence of specific disease. And when the infiltration reaches a critical level, the tissue ain’t healthy no more.
Leaky gut is a major cause of chronic inflammation. When someone has leaky intestines, undigested particles can sneak into the bloodstream. In response, the immune system generates cytokines to “kill” these particles. But these cytokines do more harm than good. Check out my prior articles for more detail on leaky gut. (link, link, link)
Along with leaky gut, there are countless other causes of chronic inflammation. Very thick books could be written. Books large enough to impress your smartest friends. But you don’t have time for that.
Instead let’s go straight to how inflammation predicts healthy aging.
Chronic disease – heart disease, stroke, cancer, etc. – usually gets people between their sixties and eighties. But in some folks, these diseases don’t arise until much later. We study these super agers to learn why this happens.
One thing we’ve found is that super agers have long telomeres. These chromosomal end-caps, the theory goes, protect against age-related DNA damage. Multiple studies indicate that centenarians have longer versions of these end-caps.
But once someone reaches centenarian status, do telomeres predict anything about their health?
It appears not. In a study of over six hundred Japanese centenarians, researchers found that inflammation, not telomere length, predicted healthy aging. This is a remarkable finding. Lower levels of inflammation, measured using biomarkers like C-Reactive Protein and Interleukin-6, were predictive of both longevity and overall health.
“This [analysis],” write the authors, “allowed us to identify low-level inflammation as, after age itself, the most important correlate of not only survival, but also capability and cognition.”
Keeping inflammation at bay
The takeaway is pretty clear: to optimize both lifespan and healthspan, we need to keep chronic inflammation at reasonable levels. One way to do this? Get to bed on time. Along with the other anti-inflammatory benefits of sleep, melatonin (the sleep hormone) has some sweet anti-aging properties.
A strong gut barrier is also crucial. There’s evidence, in fact, that centenarians have elevated levels of “good” bacteria in their intestines. These commensal bacteria, perhaps, help super agers keep inflammation at bay by preventing leaky gut.
I could go on, but the idea is that chronic inflammation degrades human tissue over time. Keep inflammation low and you’ll have healthier tissue.
Pretty important for climbing mountains in your nineties.