Ageing is the single largest cause of human suffering. It might sound counter-intuitive, but it makes sense when you think it through: all of the biggest killers in the modern world, from cancer to heart disease to dementia, affect older people far more often than younger ones.

We’ve even seen it with coronavirus, with the oldest patients hundreds of times more likely to die of the disease than children or young adults.

If you add it all up, of the 150,000 deaths that happen every day on Earth, over 100,000 of them are caused by ageing. Deaths from problems like heart disease are preceded by years of physical decline, loss of independence, and so on.

And then there’s the problems we don’t list as diseases: the frailty, the forgetfulness, the incontinence… Add all this suffering together, across billions of people, and nothing else comes close.

So, rather than tackle these individual problems one at a time, why not go after the real prize: the ageing process that causes them?

I think this is the most exciting idea modern medicine – which is why I’ve written a book about it, called Ageless: The New Science Of Getting Older Without Getting Old. To whet your appetite, these are the top 10 breakthroughs that prove this idea isn’t science fiction – from the discoveries of the past, to the cutting-edge science of the present day.

1 Dietary restriction

For tens of thousands of years of human history, ageing seemed inevitable.

However, this dogma was overturned by experiments in rats in the 1930s. Scientist Clive McCay found that rats fed substantially less than normal could live much longer than their compatriots whose food wasn’t being rationed. And, crucially, they weren’t having their time as rat geriatrics extended – they were doing so by staying young for longer, deferring the disease and frailty of old age.

Whether this phenomenon works in larger and longer-lived animals like, most pressingly, humans, remains somewhat uncertain. Plus, people who try dietary restriction report that the hunger is unrelenting, so I’m not sure whether even a few more healthy years is worth the trade-off! However, these long-lived hungry rats deserve a special place in the history of ageing research because they showed us that slowing ageing is possible.

And, as a bonus, researchers are working on ‘dietary restriction mimetic’ drugs, like rapamycin or metformin, which could mimic the effects of eating less, but without the constant hunger pangs.

2 Negligible senescence

Getting old might seem like a fact of life. It appears at first glance rather like a gradual process of wearing out, inevitable for both human-made machines and the biological machinery of living things. However, looking around the animal kingdom, we can see that there’s no law of biology mandating ageing.

I mentioned that humans’ risk of death doubles every eight years. However, some animals possess ‘negligible senescence’ – senescence being the scientific term for ageing.

Some kinds of tortoises, salamanders, fish, and a few other animals have a risk of death that doesn’t depend on how old they are. By this definition, they don’t age.

With the appropriate incentives, evolution can equip organisms with mechanisms to repair broken cells and molecules, and get rid of and replace the unfixable. There’s no reason to think that science couldn’t eventually make it possible for humans too.

3 The hallmarks of ageing

Dietary restriction and negligible senescence show us that slowing or even stopping ageing is possible in theory, but how can we do it in practice?

Enter the hallmarks of ageing. This framework was proposed in 2013, and set out a list of the biological underpinnings of the ageing process – the causes behind everything from wrinkles to cancer.

A framework might not sound like a breakthrough, but it really is. After decades of theories and counter-theories, there’s finally some scientific agreement about what causes ageing, and that means, if we can learn to slow, stop or reverse these hallmarks, we can do the same to the ageing process overall.

In fact, the rest of the breakthroughs on this list follow exactly this approach: slowing or stopping the progression of one of these hallmarks and, with it, ageing overall.