#498 Lifestyle Adds 5 Years To Your Life, But This Determines the Rest (Physicist Explains) - Dr Uri Alon

Uri Alon (0:00)

If your genetic potential is, let's say, 80 years, and you optimally combine, let's say, the top 7 lifestyle factors that we have, including not drinking, not smoking, exercising, not being metabolically unhealthy, sleep, 7 to 9 hours, self-reported good social connections, at 40, you get an extra 5 years, but at 90, it goes down to an extra year. From 80, you live to 85, but if you have none of those factors, you lose something like 15 years. You need those lifestyle factors in order to get a chance to reach your genetic potential. And if you're really good at optimizing, you can get a little bit on your average lifespan, but very little on your maximal lifespan. It doesn't push 120 But it looks to us that right now, a good number, heritability is above 50%. Now, our full genetic potential can shine out, and now we can discuss what's the remaining 50%.

Siim Land (0:50)

Dr. Uri, welcome to the show.

Uri Alon (0:52)

Ah, nice to be here. Thank you for inviting me.

Siim Land (0:55)

Excited to have you. And the reason I wanted to talk with you is because you and your colleagues recently published a paper that over, I guess, challenged some of the previous assumptions about the role of genetics and lifestyle in human longevity. So, yeah, maybe we can start with the paper, and what did you find?

Uri Alon (1:19)

Yeah, so when you look at textbooks and books on aging, you find a number that comes from Danish Twin Studies, and it says that lifespan or life expectancy, average lifespan, is about 20-25% heritable. And there's recent, more like 2018 papers looking at millions of family trees, and they claim a number less, even 10% or 7% heritable. And that has huge implications, because that means that if it's not heritable, what is it, right? Is it in our hands, lifestyle, maybe something else? And on the other hand, it's kind of weird, because we know that there are families that are long lived, and then animals, it's very heritable, and most other human traits are 50% heritable or some more. So what's going on? And we discovered in our paper that both in modern, the way we started was we looked at more modern, new data that hasn't been analyzed on Swedish twins born 1920 to 1935 So their life is very similar to ours, including all the cardiovascular, etc. And we found a heritability of 44%.

Just raw heritability. You look at monozygotic twins, dizygotic twins, and you do the regular calculation. And say, what's going on? And twins born a little bit earlier had lower heritability and twins born a little earlier had lower heritability. And then we looked at the original Danish studies, twins born 1870 to 1900 And then we said, oh my gosh, at that time, there were a lot of deaths from pneumonia, tuberculosis, 1% died before age 30 like that. That's so different from today. Yeah. So if you have a situation like that, it doesn't, who cares how long your parents lived, right? It's like your genes have very little effect if you have a lot of this, what's called extrinsic mortality. Even though, of course, there is some genetics on who dies from pneumonia and who not, but this is very minor compared to this huge effect of having early deaths on this trait you're trying to measure. Now, I want to say about heritability. It's tricky. Heritability is not a gravitational constant, but it depends on the population and the time period you're in. So it's correct that in 1870, the heritability was 20 percent because of this extrinsic mortality. Genes didn't matter that much. But if we want to look today, we want to account for extrinsic deaths. So both the new data on twins born in 1920 to 1935, where extrinsic mortality was much lower than 1870 to 900, points us in the way. But then we can also mathematically correct for extrinsic deaths. And we did that in many, many different ways. And what we found was that when you correct for extrinsic deaths, that is to say, you do kind of a counterfactual. If 1870 to 1900 had no extrinsic deaths, or if 1920 to 1935 had no extrinsic deaths, how much would heritability be? And for all of them, we get the same number, about 50%, a little bit higher. So we say that we don't know what heritability is today, because we have to wait for the twins to die, you know, etc. But our good estimate is that it should be a little bit above 50%. Now, I also want to say another thing. Medicine can correct for bad genes, so things like stents and so in the future, we can have even lower heritability again, if we can correct for all the bad genes, right? So genes won't matter anymore if you can deal with all the diseases. But it looks to us that right now, a good number heritability is above 50%.