#1

I’ve been thinking recently - everything we do has some cost, whether financial, time or opportunity cost. I assume for most of us the thing we wish for is more time, i.e. more days, months and years alive. I have been running a few numbers and thought it would make an interesting discussion topic.

A solid recommendation for exercise is 150 mins/week, which is 18.571 days per year, or 5.1% of each year spent exercising (not including preparation, travel time etc). So, by the crudest metric, exercise needs to extends lifespan by 5.1% just to break even on the time you spent doing it. Or, it needs to provide benefits in terms of healthspan and quality of life that are worth spending 5.1% of your time.

For sleep, let’s take 8 hours as the ‘optimal’. A lot of people sleep 7 hours, thus getting a clear benefit of an extra 1 hour per day of conscious waking time to do things. In context that’s a massive 4.2% extra time. If you slept only 6 hours you would net an extra 8.4%. So, if you’re a 6h sleeper, would going to bed 2 hours earlier pay off by providing a benefit of >8.4%? (In fact, considering that time awake is a premium, it would have to be even more).

I found a study (Years of life gained when meeting sleep duration recommendations in Canada - PubMed) that claims meeting the 7-9h/night recommendation gains you +1.2 life years compared to sleeping <6 hours. Another (Sleep Duration and All-Cause Mortality: A Systematic Review and Meta-Analysis of Prospective Studies - PMC) meta-analysis reckons that healthy sleep patterns get you 2.4 to 4.7 extra years. I would assume the life years is already encompassing the impacts of bad sleep on your diet, cardiovascular health etc. Obviously it has some quality of life impact, because being sleepy sucks, makes you grumpy etc. However, it seems that purely from a time basis, sleeping more is a pretty bad ROI and you won’t get that time back.

For Rapamycin, if we take a cost of around $3 USD per mg, and assume 6mg/wk, that’s a yearly cost of $936. Let’s assume an average user starts Rapamycin at 40 and has a life expectancy of 80. (We’ll ignore inflation etc). That’s a total cost of $936 x 40 years = $37,440 USD. If Rapamycin can extend lifespan by 5%, that is 4 extra years, and the cost of buying each extra year is roughly $9,360 (very reasonable IMO). If it can extend lifespan by 10%, the cost is halved.

Pretty interesting, right? Hopefully this stimulates some interesting discussion, and maybe somebody with better maths skills can make better estimates!

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#2

Interesting reasoning indeed, my first thought is the mathematical law related to the gain versus loss markers.
For example, the relationship might be asymptotic, and we may approach a state of zero benefit when extending our sleep well beyond 7 effective hours. And our gains would be maximum after, for example, 5 hours of sleep, with a lower bound below which the detriments far outweigh the benefits.
It’s a complex model, and my impression is that, as in many other issues, just a moderate effort is likely to produce the most gains.
Sometimes though the ROI with strenous effort may be nontivial, for example propensity to cardiovascular illness or cancer or metabolic disorders and so on…

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#3

Quality of life is just as important as quantity of life.
If you feel good, it’s all good.

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#4

I also like to think like this because it gives me a lot of motivation.

Exercise has an amazing ROI if we assume +7 years of increased lifespan just by spending 30 minutes per day.

For the optimizers out there, do you stack your interventions? This is what gives you the most ROI, walking + working for example.

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#5

Absolutely. I don’t enjoy exercise, and do it solely for health reasons, so I’ve always looked for ways to combine exercise with something productive. Jogging or weights, I listen to podcasts where I can learn something, or learn a language and the like. This also has the advantage of making exercise more bearable. For sleep I can’t do much, but I give myself tasks, like ruminate on a problem hoping for a solution in the morning as the brain works at night - I actually feel it helps creativity. When eating, I read, listen to edu podcasts, or watch movies/videos with dinner. In general, where possible, I try to multitask so as to maximize time usage.

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#6

Yes, that is kinda the direction my thinking is going too. 80:20 rule and diminishing returns strike again.

Of course I would say that dealing with imminent/obvious threats to longevity should be a priority. For example, getting a blood test in my late 20s, realising I had familial hypercholesterolemia, and dealing with that has probably added 20 years to my life. If somebody is diagnosed with cancer, putting huge effort into resolving that is definitely worthwhile.

IMO, I think people say this a lot, but I’m not sure how true it is. Obviously a terrible quality of life (constant pain, dementia, semi-vegetative state etc) isn’t desirable. However, I recently met up with an old family friend - a lady who is 89 years old, and has many chronic health issues. However, her husband died while in his mid-70s. I were together with their family including their grandkids (now in their 20-30s). It made me really appreciate how much difference there really is between 75 and 89. Sounds stupid, I know, but when you’re young, all of those numbers just sound “old”. However, she got to see the grandkids go into careers and buy their first house, while he only saw them as tiny kids. That is a huge payoff from a long lifespan, even if some poor health comes alongside it.

What I’m trying to say is, I think quality of life would have to be literally detrimental in order to out-weigh simply living longer.

A more realistic number I’ve heard is that exercise might add around 4 years. So, 30 minutes per day = 10,950 mins per year = 182 hours = 7.6 days per year, or ~2.1% of each year. On a 40 year horizon (let’s say 40 to 80), that’s around 7,200 hours spent, and you gain 35,000 hours (4 years). So that would be a 4.9-fold ROI on the time spent, which would be very good. Even if you look at “awake hours” and calculate based on 16 hours in a day, it still a favourable 3.2-fold ROI.

That means every 1h you spend exercising gives you 3.2h more awake lifespan in the future. I agree that it’s very, very persuasive.

(If your 7 year figure is correct, the ROI is an amazing 9.2-fold for total lifespan!)

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#7

You’re missing a few things IMO, and correct me if I’m wrong — first of all, those extra years of life isn’t a net cost of $9,360 a year, it’s obviously profitable if you have more assets like low cost index funds that can continue to compound and you enjoy, or you are still working or have income in some way. Second anything that extends maximum lifespan increases your chances of longevity escape velocity, so it might still be a good trade even if you spent most of that time working towards it.

Finally most people aren’t spending any hours they’re gaining from less sleep in a way that they benefits themselves the most. If you’re getting rid of 1 hour of sleep that might be a bad idea on net.

image
https://x.com/alexkesin/status/1957988548193447973#m

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#8

Oh, I’m very likely to be missing things or simply incorrect, haha

The cost calculation is of course very rough. But even with that worst case scenario, $9,360 for an extra year of life is fantastic ROI IMO. And you’re right that $ hopefully grows over time. It’s why all those vampires in movies are rich - imagine having index funds from the 1800s!

As for how people use their time, I really don’t know. I agree that staying up late and scrolling social media wouldn’t be useful. But how about the people who wake up at 5:00 and start being productive? For example, if you woke up 1h earlier and spent the time doing exercise and meal prep, it seems like you’re doubling effectively down on benefits compared to staying in bed.

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