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.
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.
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.
I love gaming, but I am still too young to do it properly.
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.
Probably gta 6, if it’s out by then
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.
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.
The next question would be “did they have any alternative”
I wouldn't be surprised if "health span" (although defining it is difficult) exactly mirrors the inheritability pattern of mortality.
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
Maybe even if you're still fit and strong in your 80s you should let someone else split your wood for you
https://www.thisamericanlife.org/779/ends-of-the-earth
Basically assisted death
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.
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.
Some live a very painful and limited life. Others are 85+ and still go out to run, play soccer etc. Amazing to see.
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...
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.
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.
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%?
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).
Evolution is just super super messy.
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).
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.