Health
by David A. Sinclair
Why do we age at all?
David Sinclair, a Harvard geneticist, believes ageing is a disease, and one we could learn to treat. Lifespan sets out his theory of why bodies wear down and the research he thinks could slow it. Much of it rests on yeast and mice, and other scientists dispute parts of it.
Hear a sample · read by Laura
Sinclair's Information Theory of Ageing says our cells lose information over time. The DNA mostly stays intact. What decays is the epigenome, the system that tells each cell which genes to read. He compares it to scratches building up on a CD.
When times are hard, genes called sirtuins switch cells from growing to repairing. Sinclair argues the catch is that sirtuins also keep the epigenome tidy. Each time they're pulled away to fix damage, some don't find their way back, and a little order is lost.
Sinclair thinks the survival circuit can be switched on deliberately with mild stress, such as hard exercise, cold or going hungry now and then. The idea is called hormesis. The evidence for exercise is strong. For the rest, much of it still comes from animals.
Sinclair argues that the genes you inherit explain only a small share of how long you live. The epigenome, which responds to how you live, matters more. That's why he thinks ageing can be changed, rather than simply endured.
The last part of the book asks what happens if people live far longer. Sinclair takes on the obvious worries, such as overpopulation and the rich getting it first. He's optimistic, though he admits the questions are hard.
Lost information
Sinclair thinks we age as our cells lose track of which genes to switch on, like a scratched CD.
A disease
He argues ageing should be treated as a disease, since it's the root of most illnesses of old age.
Good stress
Mild hardship like hunger, cold and hard exercise wakes up genes that protect the body.
Eat less often
Skipping meals now and then, and eating less meat, keeps those protective genes busy.
Reset
In mice, his team switched on a few genes and brought back sight in old and damaged eyes.
Hot take · true or myth?
How you live matters more to your lifespan than the genes you inherit.
True. Sinclair argues genes account for only a small part of lifespan. He thinks the epigenome, which responds to how we live, matters much more.
One thing to try
This week, add one brisk walk, swim or bike ride that leaves you out of breath. Exercise is the kind of mild stress Sinclair has in mind, and the one with the best evidence in people. If you haven't exercised in a while, check with a doctor first.
Knotd has the key ideas from 250+ non-fiction books, each in a few minutes, in plain words. Lifespan comes with a Hot Take round to make it stick.
Get the whole book on KnotdOpen in the appWhy do we age at all? David Sinclair, a Harvard geneticist, believes ageing is a disease, and one we could learn to treat. Lifespan sets out his theory of why bodies wear down and the research he thinks could slow it. Much of it rests on yeast and mice, and other scientists dispute parts of it.
Ageing as lost information; An ancient survival circuit; Good stress; Genes aren't destiny; What if it works?.
This week, add one brisk walk, swim or bike ride that leaves you out of breath. Exercise is the kind of mild stress Sinclair has in mind, and the one with the best evidence in people. If you haven't exercised in a while, check with a doctor first.
Yes. Knotd has the key ideas from Lifespan in a few minutes, in plain words, plus a Hot Take round to test them. It's one of 250+ non-fiction books in the app.
