Plateau of mortality
Biologists have questioned the existence of the limit of human life
Observations of the oldest residents of Italy have shown that the probability of their death ceases to grow at the 105th year of life. This suggests that there is no hard limit to the maximum life expectancy. This conclusion was reached by scientists who published an article in the journal Science (Barbi et al., The plateau of human mortality: Demography of longevity pioneers).
"As a rule, the chances of dying increase as a person's age increases and his health deteriorates. We found that this trend suddenly stops at the 105th year of life - elderly Italians, whom we observed, died equally often at 105 and 110 years old. This idea, the "plateau of mortality", has caused a lot of criticism in the past, and we have proved that it is fair," said Kenneth Wachter from University of California at Berkeley (in the press release Odds of living to 110-plus level out – once you hit 105).
The typical duration of human life has never been constant – before the birth of civilization, it ranged from 20 to 30 years, and then, as science and medicine developed, it steadily grew. Today, in most countries of the world, people live more than 60 years, and in Japan and other developed countries with high quality of life and first–class medicine - over 80.
On the other hand, for many living beings there is a certain maximum age determined by the so–called Gompertz law - upon reaching it, most of the animals die of old age, and the rest of the chances of dying next year begin to grow exponentially.
In recent years, scientists have been actively arguing about whether this is typical for humans. In October 2016, American researchers showed that such a maximum age may be equal to 100-115 years, which is quite modest by the standards of some biblical characters.
Wachter and his colleagues questioned these conclusions for the simple reason that the authors of the publications used data collected during surveys of the elderly themselves, many of whom, as scientists have suggested, tend to either overstate or underestimate their age. Coupled with a small number of centenarians, this, according to Wachter, has made a lot of distortions in the statistics.
Therefore, the team of Wachter went the other way – they used data that the social services of Italy collected among the oldest residents of the country from 2009 to 2015. The biological age of all the record holders, as the biologist emphasizes, was checked according to documents from the archives of all state bodies in Italy.
In total, three years ago, almost four thousand people over the age of 105 and several tens of thousands of centenarian old men and women lived in Italy. The vast majority of them are women – only 463 men managed to achieve this honorable mark.
Observing how often centenarians died, scientists were surprised to find that the chances of not living to the next birthday remained the same – about 45-50 percent – at the age of 105.
This, in turn, means that Gompertz's law does not work for people – otherwise the probability of death of the oldest inhabitants of Italy would continue to grow, and not stop at a fixed mark. In other words, there is no limit to life.
Not all scientists agree with such conclusions. Brandon Milholland, one of the authors of the concept of the limit of human life, believes that even if the data of Wachter and his colleagues are correct, this does not necessarily mean that people can live indefinitely. In this case, the limit of life will simply be much higher than the initial calculations showed.
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