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By Enginerrrd 2026-02-0315:257 reply In case anyone was curious like me: the standard deviation of lifespan is ~12-15 years in developed countries.
So environmental effects, sleep, diet, lifestyle, etc (I.e. modifiable factors) maybe account for half of that, so like 6-7.5 years of variance. Which… sounds about right to me.
Lifespan is not even half the story though, health span is much more important. Your life is completely different if you can ski or split your own wood at 80+ vs being barely able to use stairs at 50. Both might die at 90 but one "lived" 30 years more
By Sohcahtoa82 2026-02-0318:331 reply Yup.
I'm not really afraid of getting old, but I'm afraid of becoming decrepit.
My grandma has been decrepit for over 5 years now. She can't walk and has no bladder or bowel control, so she just sits on the couch and shits herself all day. She's not living, she's merely surviving. She was living with my mom for a while, but my mom decided she couldn't handle it anymore and put her in an assisted living facility.
If I get to the point where I couldn't cook my own meals and wipe my own ass, just put a bullet in me. I do not fear dying, but I do fear spending years of my life not being able to actually do anything.
My dad died at the end of last year, and was not too different from your grandma. For him the main problem was chronic pain from his failing body. Even fairly powerful opioids from a pain management doctor only helped a bit. Basically all he could do was sleep, eat meals, and sit in his chair in pain.
I feel similar to you, but I wonder if it's one of those those things where age changes your perspective. Dad was in assisted living and had several stints in rehab/nursing home facilities, and in both there were quite a few people with what I'd call poor quality of life who were still holding on to life.
By amanaplanacanal 2026-02-0320:143 reply Something we youngsters (I'm 69) may not realize is that people in assisted living still have friends and frequently even sex lives while they are there. They read, play games, and watch movies, just like us. They might not be able to do all the things they could when they were younger, but their lives are not necessarily over.
By niemandhier 2026-02-0320:332 reply I am looking forward to playing 3 decades of great computer games once I am too old to go out into the woods or do martial arts.
I love gaming, but I am still too young to do it properly.
By shermantanktop 2026-02-041:053 reply Any idea what kind of games you'll want to play by then?
I suspect it won't be hair-trigger combat games in dark dungeons where every strike results in a blizzard of gems and stars flying around the screen while teenagers scream into the mic.
But if you like Sudoku and crosswords you'll probably be good. That's my jam anyway.
I've been playing Factorio and the base game is 100 hours easily, there are mods that ratchet it up to 500+. It's great brain exercise too, constantly refactoring, solving for bottlenecks, etc.
By fragmede 2026-02-0411:35 I would love to be that mentally spry in my old age. I'm not convinced I will be though.
By niemandhier 2026-02-0413:51 Witcher, all of them Baldurs gate 3 Mass effect Assassins creed
Probably gta 6, if it’s out by then
By interloxia 2026-02-0414:26 Hopefully by then VR versions of The Longest Journey or sanctioned or unsanctioned AI generated/slop adaptations of trek/wars/who etc.
By jamesfinlayson 2026-02-043:46 This. I've bought a lot of games over the last 15 years that I haven't touched let alone finished. I hope to at least play them some day.
By nkrisc 2026-02-0322:44 Of course, some truly do “live” there, and good for them.
And others just sit there waiting to die, unable to even feed themselves.
I saw plenty of examples of both when my grandmothers were in assisted living homes. Unfortunately my grandmothers both tended towards the latter case.
By cylemons 2026-02-049:59 nice
By theragra 2026-02-0412:06 I am close to what you describe about your dad, and I am 42. I have no idea what to do. I don't want to live this way. And I don't want to die, not really, although I am at peace with the idea. I can't find what is wrong with me, except for the fact that it is related to pain regulation mechanisms somehow. This has been going on for 10 years already.
The only thing that helps now are opioids in dosages nobody would prescribe. I was prescribed opioids at some point during these years, and I still don't know if this was a mistake by the doctor. Now I am in pain AND opioid-dependent. But I am not sure I would not have ended my life sooner if not for the temporary relief I had.
The government does not allow me to get a few years of better quality life in return for dying early from an overdose, etc. I am bitter about it, and often wish government officials had the pain I do. Maybe I did not do enough, or people close to me could have been more pressing in asking to do more earlier. That's a consequence of a culture where people don't get into other people's business. I sometimes hope it is not too late still, but everything is harder now, and I still don't have any good ideas or the willpower to execute them.
By alfiedotwtf 2026-02-048:35 > there were quite a few people with what I'd call poor quality of life who were still holding on to life.
The next question would be “did they have any alternative”
It is probably more than half the story. Health span is strongly correlated to life span, although not completely. The median "health span gap" is about 10 years, and has widened by roughly one year over the past 20 years. However, this is probably just due to an aging population and not necessarily from any factors you can control fully.
I wouldn't be surprised if "health span" (although defining it is difficult) exactly mirrors the inheritability pattern of mortality.
> The median "health span gap" is about 10 years
It depends on the definition, if you're even just 20kg overweight you're living a wildly different life than you'd have if you were fit, you're closing so many doors by default and making a bunch of things much harder than they should be, But you're still considered "healthy" here
By sfn42 2026-02-047:40 This is such an underappreciated fact. Lots of people think 20kgs overweight is normal, they'll call you skinny and tell you to eat more if you're a healthy weight. An adult man of average height should probably not weigh more than 80kg. It could be okay if you're very muscular but most likely you'd be better off losing a few kilos. And being extremely muscular to the point where your BMI says overweight isn't exactly good for your health either. Though probably better than just being fat.
By circlefavshape 2026-02-0317:552 reply My Dad (age 81) tore his rotator cuff splitting wood recently. It's slow to heal and he's in a lot of pain which (along with his Alzheimer's) is really getting him down.
Maybe even if you're still fit and strong in your 80s you should let someone else split your wood for you
By jollyllama 2026-02-0418:29 I can't speak for him but the reason I want to live somewhere where I split wood at the end is so that I can expire either from want of heat when I become incapable of splitting, or so that the exertion causes me to keel over and expire in nature when it's time.
By socalgal2 2026-02-049:37 I hope I’m able to do this when the time comes
https://www.thisamericanlife.org/779/ends-of-the-earth
Basically assisted death
By droopyEyelids 2026-02-0315:541 reply It's a remarkable tragedy how many people don't understand your point.
https://en.wikipedia.org/wiki/Disability-adjusted_life_year
Too many people think your life is a binary 'living or dead' when thats not the case at all. I didn't even understand it fully till I was hit by a car.
By techdmn 2026-02-0319:59 I'm sorry that happened.
By faeyanpiraat 2026-02-0316:142 reply Yeah, been working in IT since forever (sitting work all day), but started lifting recently and it already made remarkable improvements in my wellbeing. Should've started sooner of course, but I'm still well in time.
Lot of people think it's a niche exercise activity and it shouldn't be - for all ages including those in their 80s and 90s according to reports.
By intrasight 2026-02-0316:591 reply One of the most consistent health research findings Ive heard in recent years is the benefits of weight training for older adults. Hopefully the message is being received.
By fatherwavelet 2026-02-0411:33 It is one thing to receive the message but a much different thing to act on the message.
From going to the gym for decades now, I don't see older people acting on this at all. A big problem is the CNS takes so much longer to recover as you get older. Starting lifting at an older age is really an uphill battle. I don't know a single person who has ever started lifting over 45 and kept with it. I know a guy that lifts in his 80s but our first conversation about lifting was 35 years ago. I am part of the old crowd at the gym and everyone I know has lifted for decades.
The message really needs to be that you have to start lifting young so you still lift when you are old. Need to become so addicted to lifting that you will still be doing it when your only lifting to get less weak and figuring out how to train around various injury. Not going to the gym is inconceivable to me but I just don't see how I could have started past 45. Even the difference between early 40s and late 40s lifting was night and day for me.
By klik99 2026-02-0319:12 This plus stretching / yoga has been amazing as I'm entering my 40s. For a while I was just lifting and I had strong muscles but they were short and tight. Not everyone has that problem, but just noting strong muscles are half the picture, being strong and flexible makes life feel effortless and years of being a desk jockey.
By paulnpace 2026-02-0315:33 As many of the health nutters say, the goal is "live well, drop dead."
By baxtr 2026-02-0320:18 100% now that I get older I observe the even older people I know.
Some live a very painful and limited life. Others are 85+ and still go out to run, play soccer etc. Amazing to see.
By gus_massa 2026-02-0321:36 Life span is easier to measure. You get the offial birth dates table, you get the official death dates table, you just substract the numbers and call it a day.
It is almost never reasonable to assume normality and make calculations like this. This is particularly the case when you are dealing with lifespan, which isn't normally-distributed even in the slightest. The actual ranges are likely smaller than you are stating here, and variance is just not a very practical or interpretable metric to use when dealing with such a skewed distribution.
We should be stating something like a probability density interval (i.e. what is the actual range / interval that 95% of age-related deaths occur within), and then re-framing how much genetic variation can explain within that range, or something like it. As it is presented in the headline / takeaway, the heritability estimate is almost impossible to translate into anything properly interpretable.
https://biology.stackexchange.com/questions/87850/why-isnt-l...
By Enginerrrd 2026-02-0414:281 reply Since lifespan can't follow a power law distribution, I suspect the error in variance from assuming it IS normally distributed is far less than you're suggesting.
Like even if I'm off by a factor of 2, then only ~3ish years are explainable by environment/exercise/diet/etc. Then... OK... that's really not that bad of an error in this context. That also feels a little low to me. I'd have guessed around 5-8 years anyway based on my experience with healthcare and life.
By D-Machine 2026-02-0515:40 > I suspect the error in variance from assuming it IS normally distributed is far less than you're suggesting. [...] Like even if I'm off by a factor of 2 [...]
You would be deeply mistaken. Robust statistics texts (e.g. Wilcox) are full of examples of distributions that have zero skew and are even nearly indistinguishable by eye from a Gaussian, but where the differences in variance and thus resulting differences in conclusions drawn are profound. Heck, a sample from a Cauchy distribution looks not too bad, but in fact the variance is not even defined (or effectively infinite, and, thus, meaningless).
And even if you have enough data that statistical issues are not a concern, the problem is that most summary metrics (like effect sizes, heritability, etc) are developed under the assumptions of near-normality AND minimal skew, so that the effect size can be interpreted as something about the overlap and or positioning of the bulks of the distributions. But when skew and long tails are involved, the bulk itself is what is messed up, making most such metrics largely uninterpretable.
I.e. it isn't just that variance is hard to measure accurately here, it is that, even if measured accurately, variance isn't actually a meaningful metric here.
The few metrics that do remain interpretable in such cases tend to be those like HPDI in Bayesian methods, which look at actual distribution shapes and try to quantify a bulk in a sensible location. Likewise, meaningful effect sizes for skewed and long-tailed data need to actually take into account distribution overlap in meaningful regions. Heritability does not do this, as it is an explained variance metric.
By DavidSJ 2026-02-0317:10 One note: the standard deviation of the remaining effects would be sqrt(1/2) as large, not 1/2 as large. So more like 8.5-10.5 years.
This is a nice example/re-stating of what the heritability % "means" here.
I'm curious, with something like smoking/drinking, how you can be confident that you've untangled genetic predispositions to addiction or overconsumption from those "modifiable factors". I guess that's just captured within the 50% heritability? And if you could confidently untangle them, you might find heritability is higher than 50%?
Heritability is a pretty funky concept because it's contextual to a certain point in time, environment, and population, effectively.
An example I like is that if you measured the heritability of depression in 2015, and then you measured the heritability of depression in 2021, you would likely see changes due to environmental effects (namely, there's the pandemic/lockdowns and this could conceivably cause more people to experience depressive symptoms). Let's assume we make those measurements and the rate of depression did increase, and we could tie it causally to the pandemic or related events.
In that scenario, the heritability of depression would have decreased. I don't think anyone would argue there were massive genetic changes in that 6 year time period on a population scale, but the environment changed in a way that affected the population as a whole, so the proportion of the effect on the trait which is genetically explained decreased.
For something like lifespan in the above example, you can imagine that in a period of wartime, famine, or widespread disease the heritability would also decrease in many scenarios (if random chance is ending a lot of lives early, how long the tail of lifespan is influenced genetically is much less important).
Given that note, it's generally tricky to talk about whether heritability increases or decreases, but with more accurate estimates of how genetic predispositions form you could see the heritability of certain traits increase with the environment held stable, as there's certainly ones that may be underestimated or genetic factors that aren't currently accounted for in many traits.
*edit: I realized I never mentioned the other thing I wanted to mention writing this! since you mentioned what the percent heritability means here, I think the best way to think of it is just "the proportion of phenotypic variation for this trait in a measured population which is explained by genetic variation." So it's dependent on the amount of variation in several aspects (environmental, genetic, phenotypic).
By xenadu02 2026-02-0320:52 Some epigenetic effects are semi-heritable too, eg maternal exposure can be transmitted. That's in addition to environmental effects like you mentioned. Two otherwise identical cohorts can inherit the same genetic predisposition for depression where one manifests and another does not entirely due to their circumstances.
Evolution is just super super messy.
By UltraSane 2026-02-0315:29 Lifespan isn't as important as healthy lifespan. Lifestyle can mean the difference between being able to complete an Ironman triathlon at age 80 vs being bedbound.
> the standard deviation of lifespan is ~12-15 years in developed countries.
That seems rather higher than I would have expected, at least if one corrects for preventable accidents and other such things (that I would expect to shift the results away from a normal distribution).
By D-Machine 2026-02-0317:47 Lifespan is a quite skewed distribution, so the SD looks large because it is in fact a poor summary of the bulk of the distribution. The actual part we care about for age-related mortality is narrower than such an SD would imply if we had a normal distribution (simple image example: https://biology.stackexchange.com/a/87851).
> at least if one corrects for preventable accidents and other such things
You can't really correct for these. Yes there are genuine accidents that will kill you under any circumstances, but for a lot of things both your odds of having an accident and the odds of surviving it are strongly linked to age. As a simple example, despite driving significantly less, the elderly get into more car accidents and suffer worse injuries in those accidents than people earlier in life. Only the age range of 15-24 has higher car accident fatality rates.
There is no such thing as death by old age. At most there are deaths in the elderly that don't get attributed to a specific cause (typically because of so many different things going on at once and no desire to cut up grandma after the fact to see which straw broke her back) which we tend to refer to as "died of old age" but it's not a recognized medical cause of death. People die of diseases, injuries, and various other things, many of which are strongly influenced by age but also heavily influenced by other factors.
You can set a cutoff point and say these things don't count as age related deaths whereas these others do. As long as you're consistent with these choices, you can learn something useful. But a wide enough net that is widely agreed to cover what we think of as aging is going to include a lot of other maladies, whereas a narrower selection criteria is probably going to yield wildly different results from one analysis to the next.
By peyton 2026-02-0411:49 There is death by old age. You’re just not supposed to write it on the statement because the age is there already.
By rzmmm 2026-02-0322:14 Environmental effects are not necessarily modifiable. It includes randomness, background radiation, unknown risk factors, anything which is not genetic.
>By contrast, intrinsic mortality stems from processes originating within the body, including genetic mutations, age-related diseases, and the decline of physiological function with age
So we put genetic diseases in the bucket of intrinsic mortality and then found that intrinsic mortality has a heritable component?
Yeah this paper came across to me basically as "if you ignore environmental causes of death, the heritability of death goes up"... which seems kind of circular.
Not necessarily. It could be the case that randomness plays a huge part in non-environmental caused deaths, and if that were the case we would see very little heritability.
By Jensson 2026-02-043:16 No, you randomly get cancer since cancerous mutations happens randomly. Environment can just affect chance of getting cancer, it doesn't give you cancer directly and there is no way to completely avoid cancer risk.
For example even if you live the best life possible you will still have an inherent cancer risk based on your genes and that affects the random chance of you getting cancer, it isn't a clock that says exactly when cancer will happen.
By cortesoft 2026-02-043:54 Technically, sure, but that doesn’t mean it is related to anything observable about your environment.
I really like everything Uri Alon (last author) publishes, but these types of studies have a history of inflating genetic contributions to phenotypes. Decoupling genetics from environment is not easy as they are both highly correlated.
In fact, the article discussion states: "Limitations of this study include reliance on assumptions of the twin design, such as the equal environment assumption". My take on this is that the main result of the article is probably true, but the 50% figure is likely to be inflated.
I hit the jackpot with the ultrasound technician who spoke passionately about what she believed about lifestyle risk for cardiovascular conditions and she believed quite strongly that heart disease runs in families more because lifestyle runs in families than because of genetics. She's not at the top of the medical totem pole but I can say she inspired me to take responsibility for my health than the specialist who I talked to about the results.
By cindyllm 2026-02-040:40 [dead]
By Nevermark 2026-02-043:43 Actually the opposite is true.
If the environment was significantly more varied in health impact between twin comparisons than expected, then the correlations they found under estimate the genetic component.
Noise weakens correlation. Removing noise strengthens correlations.
Some randomness is part of the signal being studied, and some is undesired measurement noise to be controlled for. And it is only the latter that is beneficial to be carefully removed or otherwise controlled for.
By marcosdumay 2026-02-0320:28 There's no prior reason to expect the cited conditions to have any specific relation to genetics. Any of them could easily be caused or accelerated by environmental conditions.
And, in fact, it looks like they half-of-are.
By laughing_man 2026-02-0320:011 reply I thought the implication was lifestyle isn't as important as we previously believed.
By dash2 2026-02-0321:04 Yeah, it’s important to note that heritability is a statistic about today’s population, not a deep natural parameter that tells you about causality. Heritability of smoking went up when smoking became less socially approved, for example.
Keep in mind this research is based on correcting twin study heritability estimates for confounding effects. However, new research shows that heritability estimates derived from twin studies are themselves dramatically inflated: https://open.substack.com/pub/theinfinitesimal/p/the-missing...
For a counterpoint to Sasha’s view, you should probably check out https://open.substack.com/pub/astralcodexten/p/the-good-news...
Anyone who cites Jordan Lasker and Kierkegaard on heritability discussions is not someone you should take seriously.
I work in the field and I think he is quite good at providing a fair layman’s overview. He’s also famous (or notorious) for having few barriers in terms of who he reads/responds to.
One of these guys he’s citing has identified himself as a Nazi. Maybe Scott should start exercising a little discernment here. Regardless, he’s making a pretty weak argument against Sasha’s interpretation of the study.
By abc123abc123 2026-02-0412:04 OMG! Burn the witch!
