On the day he turns eighty, Nature gives a mathematical birthday present: a gradual reprieve from the relentless likelihood that he or she will die in the coming year.
This gift may seem like a small desolation against the growing creaking of the joints and the still-increasing likelihood that the end is near. But an analysis of nearly 4,000 very long-lived Italians suggests that the increase in the risk of impending death slows to the age of 105 years. Afterwards, the researchers estimate that the likelihood of her seeing another birthday is about the same 50-50
Maybe it's "nothing to blow a trumpet about," said Berkeley Demographer Kenneth Wachter of the University of California. But at least the mortality rate is dwindling, according to the data.
Wachter and colleagues from universities in Italy and Germany published their findings in the latest issue of the journal Science .
For humanity in general These findings point to a fascinating, albeit largely theoretical, perspective: that the maximum possible human lifespan ̵
In principle, if the "oldest elders" tell us how long we could live, many centenarians could even get older. And maybe even older with the right elixir.
"These data suggest that our genetic heritage is permissive," Wachter said. "Our bodies are not so composed that at some point everything goes wrong."
In fact, he said, there is reason to believe that some people might beat the current longevity record of 122 set by Jeanne Louise in 1997 Calment of France
The new research is contributing to a debate, the poets and philosophers occupied as long as they put on paper. For example, the historian Gaius Plinius Secundus, better known as Pliny the Elder, considered a number of long-lived individuals and considered the importance of their longevity.
Scientists have been in dispute since at least 1825 The British mathematician and actuary Benjamin Gompertz published the first models of human mortality and asked when and if we must die.
In the new study, the international team of demographers and statisticians used the proliferation of people who have survived far to their 100th birthday. By calculating and analyzing the mortality rates from 3,836 well-documented cases of Italians living 105 years or more, and combining that data with existing mortality data, researchers constructed a statistical model for the statistical probability of death in each year of the human lifespan from 65 to 105.
Established demographic data show that people die every year after age 65. And mathematics is unforgiving: every year after the age of 65, the likelihood of death increases at a rate twice that of the previous year.
But when the researchers added to the earlier data the 3,836 long-lived Italians, they saw that doubling lasted only until the average man's 80th birthday. Thereafter, the rate of increase slowed.
For the lucky people who made it past 105, this annual increase in the likelihood of death seemed to stop.
The authors also showed that the annual mortality rate for individuals over the age of 105 decreased slightly with each additional year of birth, so those born more recently tended to live longer.
This pattern strongly suggests that longevity continues to increase over time and that a limit, if any, has not been reached, "wrote the team, which included demographer James W. Vaupel of the Max Planck Institute
"Our findings contribute to a rekindled debate over the existence of a fixed maximum lifespan for humans," they added, "in any case it casts doubt that a limit is still in sight is. "
To epidemiologist of the University of Illinois S. Jay Olshansky, the proof of the counter-argument – that there is a strict limit to the maximum human lifespan and we have already achieved it – is right there in the new Italian data.
"The conclusion that they came to the conclusion that there is no upper limit to life is unreasonable," said Olshansky, who was not involved in the new research t.
When people reach these extreme times, at least half disappear every year. And with so few of them, this harsh reality tells us "the true story," he said.
"If 100 people survive to make billions of people over the age of 110, what exactly happens? Does it matter if 50 or 60 die before their next birthday?" He said. It's just not convincing to use such a small difference coming from such a tiny human population to say something about the longevity of people in general. Statistically he said: "The tail of the survival distribution does not wobble with the dog."
This should be clear to anyone who has ever been near senior citizens, he noted. "Human bodies are not meant for long-term use, and if we manage to operate them for more than a century, many age-related illnesses accumulate," Olshansky said.
Geneticist Jan Vijg of the Albert Einstein College of Medicine in New York believes he has seen the limit of the human lifespan, and said that it has stopped its ascending path in the 1990s with the death of Calment. (The Frenchwoman attributed her longevity to the fact that she did not care much and had a diet rich in olive oil, port, and chocolate, which she consumed at a rate of more than 2 pounds per week.)
For A study published in 2016 in the journal Nature calculated Vijg and his colleagues that if scientists could bring together 10,000 people together who reached the age of 110 – a great if – only one of them expected would live beyond 125.
Vijg, who was not involved in the new study, praised the authors' ability to create a new and well-documented database of very long-lived individuals.
But "their data does not support the claim that the maximum limit for human life goes much further than before," he said.
"There is an upper limit and there is a blanket at the end of the day," says Vijg.
Vijg says he is "astonished" at the power of the scientific debate on a topic that is so far removed from the reality of ordinary mortals. The outer limit of human life is a "fascinating scientific debate," he said. But improving people's average life expectancy – by increasing nutritional gains, creating new medicines and tackling the causes of infectious diseases – is a better way to spend their energy.
"There are many possibilities here, no doubt," Vijg said. "We can improve the quality of life and maybe give more lives to more people."
What do the new numbers about life and death tell us at the outer limits of human life?
Think of aging as if it were a treadmill: In the early '60s, you walk around powerfully and around the time of your 65th birthday begins the speed with which the treads move underfoot.
The speed increases every year. In fact, the rate of this change doubles every year.
Do not keep up and you die.
At the time of your 80th birthday, the rate of this increase is beginning to slow. It is more likely that you die each year than the year before, but your treadmill does not accelerate so quickly.
And when you reach the age of 105 – surprise! – The annual animation stops altogether.
Now imagine a gym filled with treadmills each staffed by people of different ages. The 105-year-olds run faster than anyone who is younger. And they fall from their treadmills – dying – much faster than the 70-year-olds.
In fact, only about half of them make it to 106.
But when they do, they get a little break: their treadmills are still the fastest in the gym, but at least they're not going faster.