In the world we now live in, the first step in answering a question is to just ask GPT.

From Bing AI:

While clunky, the answer is generally correct. Although, I’m not sure where the fact “people spend one-fifth of their life with a chronic illness” comes from. I asked Bing to provide the source and it pointed me generically to the CDC. After searching around a bit, I found that, as of 2018, 63.4% of people aged 45-64 and 87.6% of people over the age of 65 had at least one chronic condition.¹ Given a life expectancy of 76.4 years for people in the US, I suppose it’s reasonable to assume people spend, on average, about 1/5th of their lives with a chronic illness.

Back to definitions:

• Lifespan is the total number of years a person lives, irrespective of how healthy they are during that time. It’s a rather simple heuristic because it’s usually fairly easy (but, of course, sometimes difficult) to determine when a person is alive.

• Healthspan is the amount of time a person is alive and healthy. It can never be greater than lifespan and is usually a lot less. Unlike lifespan, this definition is much fuzzier. How do we objectively determine “health” across all people?

Past

Healthspan is a relatively new concept. In the olden days, lifespan and healthspan were pretty much the same. You’d walk around hunting and foraging until you got hit by a falling rock or succumbed to tuberculosis, yellow fever, smallpox, malaria, cholera, or the plague.

Needless to say, life was poor, nasty, brutish, and short.²

But then, people like Alexander Fleming discovered things like penicillin and all of a sudden we started to pass level one in this game of life. Doctors began to realize washing their hands was actually important, we invented things like sewers to carry waste away from the streets it was previously dumped on, and medical techniques improved to the point where people now regularly live to over 100 years old.

Present

Yet, as we’ve increased lifespan we’ve also started to uncover new health issues like a paleontologist digging up a T-Rex.

Cancer, heart disease, and alzheimer’s (just to name a few) are relatively new phenomena. You likely wouldn’t find many people in the early days of humanity dying because they didn’t have access to a triple bypass (although, atherosclerosis does exist in mummies that died at old ages!). It was mostly due to the falling rocks and tigers and using sidewalks as sewers. It was not because these folks were on the paleo diet.³

So, we’ve managed to do really well on the lifespan front - just look at the chart above. Yet, we’re stagnating a bit on the healthspan front. People are living longer but those longer lives are uncovering these diseases that predominantly affect older people - diseases of age.

Future

The power of longevity treatments is their ability to address both the lifespan and healthspan issues simultaneously.

Many diseases - such as the ones mentioned above - are highly correlated with aging because they are caused by mechanistic processes of aging. We’ve previously covered 12 of these.

Take liver fibrosis, for example. Non-alcoholic fatty liver disease (NAFLD) can be caused by a variety of factors, one of which is the senescent state cells can enter as they age. In this senescent state, cells become zombie-like; they are alive, consume nutrients, and look rather cell-like yet don’t actually function as they cell type they are supposed to be. What’s worse, they tend to throw off inflammatory molecules which damage surrounding cells and tissues, further exacerbating the problem.

One area of anti-aging research centers around removing these senescent cells. If a hypothetical drug were able to remove or reprogram these cells, you would wind up with a liver that was fully healthy. This obviously not only leads to a healthier person but one who can live longer. Thus, we’ve simultaneously increased both healthspan and lifespan.

Longevity is not just about increasing lifespan. Treating the root causes of aging has the potential to wipe out many of the chronic conditions we face today. By targeting the mechanistic processes of aging, we can actually get at what causes these diseases in the first place.

So, when we think about healthspan vs. lifespan it’s less about one or the other and more about how to tackle both simultaneously.

Cheers,

[1] Chronic conditions as defined by the NHIS survey are: arthritis, cancer, chronic obstructive pulmonary disease, coronary heart disease, current asthma, diabetes, hepatitis, hypertension, stroke, and weak/failing kidneys.
[2] This is a somewhat misappropriated usage of Hobbes’ description of humanity in Leviathan
[3] This is a fun statistical game anyone can play. Let’s say you make the claim “nobody in ancient times died from heart disease because they were on the paleo diet, therefore people today should be on the paleo diet and they won’t have heart disease.” A reasonable person would point out that heart disease is an older person’s disease and therefore nobody in olden times would have had it because they all died before it could ever set in. This is a free lesson in how to sell lots of dieting books.