Comment by tacon 4 days ago
On some podcast a longevity doctor asked the host to estimate how much longer the average person would live if we eliminated/cured cancer.
The answer was about three years. Eliminate heart disease? Another three years. Eliminate both? About five years.
The thing is that we are led to believe that cancer just strikes at random, and anecdotally we know of someone that never smoked to get lung cancer that spread everywhere to strike them dead.
Yet we also know it is not quite like that. If you smoke, drink, make sculptures out of asbestos dust, eat processed meats, shoot depleted uranium rounds down at the range and work with radium in a gun sight factory then you probably have stacked the odds.
Now imagine you have an identical twin, maybe not cojoined, but living with the exact same stacked odds. However, you eat a strict diet of highly processed foods and only play tiddlywinks for physical activity. Meanwhile, your twin rides eats a strict diet that is mostly whole food, plant based and gets a lot of physical activity due to a passion for dancing.
One of you is going to be likely to suffer a cardiovascular event before the other and that same person is going to run the risk of catching cancer first.
Now we all know that eating processed foods, maybe with the exception of processed meat, isn't going to 'give you cancer' and neither is playing tiddlywinks. Equally, a few extra antioxidants and a bit of fibre from eating a few more carrots isn't going to spare you from cancer, neither is dancing for that matter. Nonetheless, cardiovascular and gut health is important for reducing cancer risks.
I say this with anecdotal evidence provided by a car dependent relative that chose not to eat a fibre rich diet and now has cancers that I would not wish on anyone, with his digestive tract having to be trimmed from the far end due to cancer.
Because he took the medical route with meaty pies and moderate alcohol levels, his life might only be cut short by three years. However, by then, there will be two decades of extreme medical interventions and a smorgasbord of medications that have to be taken daily. Lifespan is not as important as healthspan and there is much we can do through diet and physical activity to maximise healthspan.
The trouble with my relative is that advice to go absolutely teetotal, stay off the processed meats and to eat fibre (as in vegetables) was not a message that was well received. This advice is in line with WHO recommendations but this can be simply ignored once lifestyle choices have been decided on.
This is getting scarily close to “most people who get cancer only have themselves to blame” which can be a comforting thought if you’re putting in a lot of effort to reduce your own risk of cancer but at the end of the day it’s not true and kind of a shitty thing to say when we’re commemorating someone who fell victim to this horrible disease.
Reduce the odds it’ll get you too as much as you want, you’re wise to do so, but keep in mind it can still get you too and it is never somebody’s own fault.
More importantly, you can (almost) never say that if a cancer patient had done this and that or not done such and so they wouldn’t have gotten sick. You just can’t know and even if you did it’d still be a shit thing to say.
> Yet we also know it is not quite like that.
Oh, come on.
Even if you're correct and cancer is not completely random but rather has clear causative factors, a lot of those factors -- perhaps the majority -- are uncontrollable.
Radon exposure. Naturally occurring radioactive isotopes or beryllium in your vegetables or water. That virus you fought off a few years ago. That course of cyclosporine you once took. That cosmic ray from the Andromeda galaxy that happened to hit you and scramble some DNA. Many, many other factors. Cancer strikes in ways that seem truly random because many or most of its causative factors have absolutely nothing to do with lifestyle choices.
Exactly. There are definitely people who lead higher risk lives by having exposure to carcinogens, but even that has some randomness to it. I had a family friend that smoked like a chimney his entire life, and died in his late '80s with tar-filled but cancer-free lungs. Another was an x-ray tech in the earlier days before they took nearly as many precautions as they do now to protect the technicians. No cancer.
Contrast this with some aunts and uncles who lived relatively clean lives, and still ended up dying of different cancers. Sure, I don't doubt there is a cause if we dig deep into it, but there's still some randomness.
I hear what you are saying, however, the vast majority of toxins that enter our bodies come through our mouths and out of choice. Some of these toxins, such as alcohol, cigarettes or processed meats are known to be carcinogens.
There is a very different level of dosage involved, that one cosmic ray from outer space that one time is vastly outnumbered by the trillions upon trillions of atoms that could be carcinogenic that come through the mouth, typically on a daily basis, for decades.
The body is pretty good at taking out the trash, including the mutant cells that did not reproduce properly. This goes on all the time. One cosmic ray from outer space might scramble some DNA but your body can deal with that as an isolated incident, the mutated cell(s) just get taken out with the trash.
If you overwhelm this system with too much garbage for the body to deal with then that is a causative factor that was not controlled.
It is helpful to see things this way because it enables a sense of perspective. It is not going to be 'forever chemicals', 'insecticides' or anything like that, you need to worry about. What goes in the mouth rather is what counts rather than these theoretical other things.
This means taking seriously what research in cancer, diabetes and other disease has to say. For cancer there is clear advice on what to avoid, same with diabetes and much else nobody would wish on anyone. It is defeatist to be in denial about this to assume that random cosmic rays play as much a part as the garbage we willingly consume when it comes down to it.
Eh, it's still a numbers game. Changing your chances of contracting terminal cancer in the next 5 years from 1% to 0.5% is still significant.
In this case, the specific percentages are all the significance. When a lot of the factors are controllable and a lot of them are uncontrollable, the most reasonable question is "How much do the controllable factors actually change the odds?"
> Changing your chances of contracting terminal cancer in the next 5 years from 1% to 0.5% is still significant.
Short of quitting smoking, there's almost no way to do that, because you don't know what the factors are or how they're weighed & influenced by individual genetic, immune, and metabolic factors.
> "How much do the controllable factors actually change the odds?"
Not only does nobody know, nobody has the foggiest notion. I've never seen a relevant population-wide observational study that wasn't so full of methodological flaws that you could spend hours picking apart its defects.
Of course we know that there's a set of factors associated with the development of cancer -- like, e.g., long-term exposure to polonium in drinking water -- but there's also a large set of factors that nobody is aware of or which can never be controlled for. To use only the first set -- the set of what we know and can control for -- to accurately estimate the odds of contracting cancer within the next five years is impossible.
Maybe looking at the average is the wrong thing to do. People who die from cancer can be robbed of a lot of years. A couple of other recent cancer deaths I saw on HN:
Walter Ehmer died at 58 https://news.ycombinator.com/item?id=41490388
Jake Seliger was also known on HN died around 40: https://news.ycombinator.com/item?id=41201555
I find those estimates believable in a narrow interpretation of the question - i.e. if we solve cancer but change nothing else. I would expect a longevity M.D. to understand the spirit of the question and answer accordingly, though. I'm curious which podcast / doc this was?
It's true that solving cancer, heart disease, and even all other similarly deadly diseases, would not automatically mean humans living indefinitely, because there's still cellular senescence to contend with.
Fortunately, we've effectively solved senescence (or at least it seems we're well on our way). Check out the picture of the twin mice from David Sinclair's lab (https://sinclair.hms.harvard.edu/research) - it's hard to believe the two mice were born at the same time...
And if I recall correctly, they didn't even do any sort of telomere modification in that study either... Don't quote me on that. But telomeres are another potent avenue towards >10x extension of life span, and also as it turns out, fairly trivial to lengthen and thereby allow a cell to continue mitosis indefinitely.
The problem to solve is cancer, though. Telomeres limit the number of times a cell can divide by design, and seemingly the purpose of limiting division in the first place is to mitigate risk of developing cancers.
This sounds surprisingly short. Surely the average person with cancer isnt going to live just three additional years?
Went and did a brief lookup (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6710558/) - life expectancy is reduced by at least 3 years, even for the oldest patients, and increases significantly as age at diagnosis goes down.
I suppose from the perspective of an 80 year old, curing cancer would in theory increase life expectancies by ~ 3 years, though I wonder how many people die of "old age" but have an undiagnosed cancer of some form contributing.
It's because of the Gompertz mortality law [1]--the probability of dying at a certain age is exponential. If you assume that the mortality of each age-related terminal illness itself follows the Gompertz law, then eliminating any one of those illnesses won't affect the overall life expectancy much, because exponential growth is so powerful. Even if we had cures for all age-related diseases except, say, Alzheimer's disease, the fact that Alzheimer's disease mortality also follows the Gompertz law (probably a reasonable assumption) would lead to lifespans not dissimilar from our present ones.
Essentially, in order to achieve dramatically longer lifespans, we would need to eliminate, or at least significantly slow, all aging-related causes of death.
[1]: https://en.wikipedia.org/wiki/Gompertz%E2%80%93Makeham_law_o...
Keeping the body alive is a low bar.
Lost quality-adjusted life years would be a better measure. Many people survive for many years with cancer, but the quality of life drops significantly.
Most people don't have cancer, so the average lifespan reduction of everyone is going to be quite a bit lower than the average lifespan reduction of people diagnosed with cancer.
My total guess(!) is because relatively few people lose a large number of years to cancer, due to both the median age of diagnosis and long term survival rates of some common cancers being high? (For example, breast cancer has a 75% 10 year survival rate with a median age of diagnosis of 62. Bowel cancer is about 60% and 71 respectively.)
Three years would be an amazing amount of precious time with a loved one. I know this.
This reminds me of a video I saw on HN yesterday: https://www.youtube.com/watch?v=CJkWS4t4l0k
Was this a well-corroborated and fact-based opinion, or was it off-the-cuff and handwavey? Podcast answers aren't always totally reliable.
But you mention "the average person," which is really the crux of the matter. Cancer strikes perfectly average people, oftentimes in their 30s or 40s, and hands down death sentences at random. A bad roll of the dice. A stray cosmic ray hit a dividing cell. Who knows? That is what is scary.
Eliminating cancer may perhaps only increase the average lifespan by three years -- though I have my doubts -- but what's much more important is that it would cut down tremendously the number of premature and random-seeming deaths in the prime of life.