Living to the limit

Despite rising life expectancy, we may be approaching the natural limit of human lifespan, new research has shown.

There has been a steady and substantial rise in life expectancy over the past 150 years, from under 50 to nearly 80 years. But, during the last twenty five years, the number of people reaching extremely old ages has not increased, which, according to Professor Jan Vijg, suggests that humans have a natural lifespan limit of 115 years.

Nevertheless, that does not mean that there is a fixed age beyond which humans cannot live, only that the chances of surviving to, for example, 125 years are extremely low. One Frenchwoman came close in 1997, when she lived to the age of 122.

"If there were 10,000 worlds like ours, then you would expect just one person per year to reach the age of 125," says Vijg.

Public health care has been was very successful in reducing early-age mortality with more people than ever reaching the age of 80.

But, in the new study, published this week inNature, Vijg和他的团队Albert Einstein College of Medicine in New York, analysed data from the Human Mortality Database and the International Database of Longevity.

The longest lifespans, they found, have not increased for the last two and a half decades.

"For a while, we were extremely successful in reducing mortality in all age groups, also [in] older people. However, now you see diminishing returns and we show that the reduction in mortality for the oldest old is very little and over the last years there is actually no progress there," concludes Vijg.

In fact, the data levels off at an age of 115 years, suggesting that this may be the natural limit for most of us. Some will still surpass this limit though, because our cells won't suddenly self-destruct on our 115th birthday. The exact biological basis of this apparent age-limit is still unknown though.

While living forever may seem off the cards for us, some species are approaching immortality, like the jellyfish Turritopsis dohrnii which can regress back to a polyp from any stage of its lifecycle. So the fact that a semblance of immortality can occur naturally, even if it is rare, opens a door for advances in biomedicine and technology: could we all live forever like the jellyfish?

Vijg thinks it would be unlikely, suggesting instead that we should focus our efforts on increasing the period of an active and healthy life instead.

"We must work on possible interventions... It would be fantastic when, a couple of decades from now, we have been successful in keeping a lot of 100-year-olds who can still live independently."

So while we probably won't make our 150th birthdays, we can still hope to enjoy longer periods of healthy living. Cheers!