Andrew Steele
speaker
169 appearances
2 recordings
2 series
first heard Feb 2021
last heard Nov 2024
Andrew Steele’s voice in public audio — every appearance, attributed to the second.
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Appearances
I think my favorite of these is to brush your teeth. What we've discovered is that people who have worse oral health actually have a higher risk of heart disease. There's maybe even a link with dementia because the bacteria that cause gum disease have been found in the brains of people who've got dementia.
I mean, that's exactly right. And I think one of the big challenges that I've overcome is to explode people's conventional wisdom about what aging is. But what I mean by aging as a biologist, actually, the simplest definition isn't a biological definition at all. It's a statistical one. And it's simply how fast your risk of death increases with time.
As a human, our rate of aging as a species is that our risk of death doubles about every eight years. So let's try and put that into some kind of context. I'm 36, and that means my odds of death this year are about one in a thousand. And actually, you know, I quite like those odds. If that were to continue for the rest of my life, I'd live into my thousand and thirties on average.
But of course, that isn't what happens. My risk of death will carry on doubling every eight years. And so that means if there are no advances in medical science between now and me, you know, fingers crossed making it into my nineties, my odds of death by then will be one in six per year, life and death at the roll of a dice.
And so, you know, as a biologist, you look at this and there's this exponentially increasing risk of death with time. That is the problem that we call aging.
Yeah, I guess you've got to look at that as 0.1%. And actually most of that, when you're my age, is still down to external things. We call them extrinsic forms of mortality biologically. So that's things like car accidents and unfortunately suicide is a really big cause of death for men at my age as well.
So it's not generally the sort of cancers and the heart disease and that sort of stuff that you associate with older age. It's the external causes of death. And then obviously as you get older, the risk of diseases increases and starts to swamp those external causes.
Well, this is the fascinating thing because obviously that happens to cars, it happens to machines, it happens to our pets, it happens to our farm animals. You know, you can easily imagine that aging is a universal process. But actually this just isn't the case because we've got a huge advantage as biological organisms. We can repair ourselves.
If we didn't have these incredibly intricate mechanisms of repair that are buzzing away inside of our cells every single hour of every single day, all the time, you know, correcting mistakes, disposing of rubbish, that kind of thing, we would die an awful lot sooner than we actually do.
And in fact, there are some animals that have got so good at repairing themselves that their risk of death doesn't change with time. That's a phenomenon that in biology we call negligible senescence. So negligible just meaning, you know, not much, and senescence is just the biological term for growing old.
So the reason there's a tortoise on the cover of my book is because that is a negligibly senescent animal. It's an animal whose risk of death stays constant when it becomes an adult. And that means that they can live an incredibly long time. But most importantly, it's not just their risk of death that stays constant. They also don't have any increase in frailty as they get older.
They stay reproductively active no matter how old they are. That means that they grow older, but without growing old in the way that we humans do. And so I hope that by understanding the biology of aging, we can try and transfer some of that wisdom and some of those sort of biological techniques to keep us sprightly into our old age too.
The goal is definitely health, and I think that you've got to think about what actually kills you. Although decades ago it was permissible for doctors to write death by old age on an older person's death certificate, now we understand that you can't just die of old age. You die of heart disease, you die of cancer, you die of dementia.
One of these diseases that are much more likely as you get older, and these diseases too get exponentially more likely as you increase in age, that's something that eventually becomes severe enough to take your life. And so, you know, it's very much the pain, the suffering, all of these things together that we want to try and get rid of.
And actually, it's a really good way of thinking about it, is to think about a lot of modern medicine seeks to treat individual diseases. But even if we had, hypothetically, a complete success treating an individual disease, and let's take the example, imagine that, you know, we cured cancer tomorrow. That would only add about three years to human life expectancy.
And that's because, you know, if you avoid getting cancer, you've probably already got a bit of heart disease or diabetes or, you know, dementia starting, you know, waiting in the wings to kill you as you get older. And so that means that it doesn't make you healthier for much longer.
Whereas by treating the aging process, the thing that causes all of these diseases, we can potentially defer those diseases, maybe even prevent them entirely and create a lot more healthy years for people.
These are all good ideas, and they're definitely something that I would encourage people to do, but the fact is we can go beyond this with medicine. And I think the best way to explain this is with an example.
One of the biological processes behind aging is the accumulation of aged senescent cells, and they build up in our bodies as we get older, and we know that they're responsible for a whole range of age-related diseases. And we've also got drugs that can kill those senescent cells while leaving the rest of the cells in the body intact.
So we've done experiments using these drugs on mice, and we wait till the mice get to about 24 months old. Now mice obviously have a much shorter lifespan than humans, so that's something equivalent to about 70 in human years. So that means we give these old mice the drugs, it clears out those aged cells, and what we find is that the mice basically get biologically younger.
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