Living to 120

WANT TO LIVE longer? For centuries the attempt to stop ageing was the preserve of charlatans touting the benefits of mercury and arsenic, or assortments of herbs and pills, often to disastrous effect. Yet after years of false starts, the idea of a genuine elixir of longevity is taking wing. Behind it is a coterie of fascinated and ambitious scientists and enthusiastic and self-interested billionaires. Increasingly, they are being joined by ordinary folk who have come to think that the right behaviour and drugs could add years, maybe decades, to their lives.

Living to 100 today is not unheard of, but it is still rare. In America and Britain centenarians make up around 0.03% of the population. Should the latest efforts to prolong life reach their potential, living to see your 100^th birthday could become the norm; making it to 120 could become a perfectly reasonable aspiration.

More exciting still, those extra years would be healthy. What progress has been made in expanding lifespans has so far come by countering the causes of death, especially infectious disease. The process of ageing itself, with its attendant ills such as dementia, has not yet been slowed. This time, that is the intention.

The idea, as we set out in our Technology Quarterly, is to manipulate biological processes associated with ageing that, when dampened in laboratory animals, seem to extend their lives. Some of these are familiar, such as severely restricting the number of calories an animal consumes as part of an otherwise balanced diet. Living such a calorie restricted life is too much to ask of most people; but drugs that affect the relevant biological pathways appear to bring similar results. One is metformin, which has been approved for use against type-2 diabetes; another is rapamycin, an immunosuppressant used in organ transplants. Early adopters are starting to take these drugs “off label”, off their own bat or by signing what amounts to servicing contracts with a new class of longevity firms.

Another path is to develop drugs that kill “senescent” cells for which the body has no further use. The natural means for disposing of these cells, like a number of other repair mechanisms, themselves weaken with age. Giving them a helping hand is not just a matter of tidying up. Senescent cells cause all sorts of malfunctions in their healthy neighbours. “Senolytic” drugs which target them pose obvious risks: it is hard to kill off one type of cell without inconveniencing others. But the promise is clear. For true believers that is just the beginning. Groups of academic and commercial researchers are studying how to rejuvenate cells and tissues by changing the “epigenetic” markets on chromosomes, which tell cells which genes they should activate. These markers accumulate with age; strip them back and you might produce the cells of a 20-year-old body inside one that is in fact 65. Mimicking calorie restriction and clearing out senescent cells would delay ageing. Boosters claim that epigenetic rejuvenation could halt or reverse it.

One cause for concern is people’s brains. Slowing bodily ageing will not change the fact that the brain has a finite capacity and is presumably adapted by natural selection to conventional lifespans. This is quite separate from worries about dementia, which is caused by specific diseases. Society will thus have to find ways to adapt to the normal ageing in brains: centenarians may, for instance, find themselves increasingly occupied with asking their AI diary assistants questions for which once they would have remembered the answer.

An even greater concern is that none of these ideas has yet been tested formally on people. That is partly because drug – approval agencies do not yet recognise old age as a treatable condition, making trials hard to register. By their very nature, such trials must follow thousands of people over many years, adding to their cost and complexity. The lack of testing is also partly because many of the initial proposals use out-of-patent molecules that are of little interest to drug companies. Nevertheless, some trials are now in the works. The Targeting Ageing with Metformin trial (TAME) will follows 3,000 Americans in their 60s and 70s to see whether the drug does in fact aid survival overall. Such studies will necessarily take time. But more of them are needed, and governments should be helping bring them about.

Any development that causes people to live healthily for longer, and to take fuller advantage of what the world has to offer, is cause for cheer. Some people, observing billionaires’ interest in longevity-promoting startups, worry that the benefits will be captured mainly by the rich, leading to a class of long-lived Übermenschen lording it over short-lived ordinary folk. But technologies have a record of spreading and cheapening as they do so. It is hard to imagine a privilege more likely to spark rebellion than a ruling class that hoards age-treatments to escape the great leveller.

The fact of many people living much longer would have wide ramifications. Most obviously, working lives will be extended, as they have already as life expectancies have lengthened, and possibly even more so for women, who will lose less of their careers to having children, perhaps narrowing inequality in the workplace. Over time there could be deeper shifts. People who live longer may care more about threats that are further away, such as the state of the world in 2100. Longevity permits that patient accumulation of capital, a factor in the emergence of a middle class. And times when political power is exercised mainly by young men, such as the Middle Ages in Europe, tend to be more violent than when older, cooler heads prevail. Families will span even more generations and, presumably, larger networks of exes, half-siblings, and quarter-cousins. Will that atomise them, or bring them together? Will a surfeit of centenarians marginalise the young, create a cult of youth – or both?

For ever and a day

People will seize on the elixir of life if it becomes available. Natural selection has no interest in indefinite longevity per se: the traits that spread best are those that make organisms fit in their prime; those that help them live on when reproduction is a distant memory must work through children and grandchildren. Yet the visceral drive to cling to life is the most basic trait of all. Indeed, it is prevailing today – to tantalising effect.