A controversial study suggests that there is no limit to human aging

The older we get, the greater our chances of dying. Or at least that's what we thought. A new study suggests that mortality rates stabilize after 105 years, and that no upper limit exists for human life span. It's an extraordinary finding – that is not going very well with other aging researchers.

In 1825, British mathematician and actuary Benjamin Gompertz noticed a strange quirk about human aging and mortality. Our risk of dying, he observed, is increasing exponentially as we get older. Scientists now refer to this as the Gompertz Law of Mortality, and it has remained largely intact since it was documented nearly 200 years ago.

Once we enter adulthood, our chance to die doubles every eight years. But as Gompertz himself admitted, there is simply not enough data to prove that this trend is true for the oldest of the elders. Research published over the last 10 years, however, continues to support Gompertz's model, including a study in 2017 that showed that super-seniors – people who live 110 years or older – still experience accelerated mortality rates at the same time. over time.

Some scientists have begun to question the Gompertzian paradigm. A controversy has emerged that suggests that mortality plateaus – in which mortality rates slow down and even stop – exist for humans and animals beyond a certain age. There is now an active debate among aging experts as to whether mortality rates continue to accelerate and / or increase exponentially to extreme age, or whether they will continue to increase. they end up cap.

New research published today in Science suggests that a mortality plateau does exist for humans, and that the Gompertzian model breaks down after age 105 years old. The authors, led by Elisabetta Barbi of the Department of Statistics at Sapienza University in Rome, say their data suggest that there is no upper limit to life – at least, no limit which has been observed yet.

Some of the experts with whom Gizmodo spoke, however, said that this rather breathtaking conclusion was totally unjustified, and that the researchers had made many errors and misinterpretations to achieve their results.

A fundamental problem in research on aging is the extreme poverty of the data. Only a handful of people live beyond 105 years and even fewer live beyond 110 years. For the new study, Barbi and his colleagues sought to overcome this limitation by examining data collected by the Italian National Institute of Statistics (ISTAT). This unique dataset contains recently collected and validated data on the individual survival rates of all Italian residents aged 105 years and over from January 1, 2009 to December 31, 2015. The researchers used this data to create their own database. unique data of very old people. to produce estimates of mortality rates at extreme ages.

For analysis, researchers examined 3,836 individuals, of whom only 463 were men (12 percent). Less than 4% of these people were born abroad and a significant share comes from a clear Italian heritage. Some 2,880 deaths were observed in this group of samples over the seven years, which meant that the remaining people were still alive at the time the study was completed. The cause of death was not a factor, as this study focused strictly on mortality rates.

Data Mortality rates increased exponentially until about age 80, but they subsequently decelerated, reaching or reaching 39, approaching a plateau after 105 years. For both men and women, the probability of dying at 68 was about 2%. to die at 76 was about 4 percent. At age 97, the odds have risen to about 30%, and at 105%, the probability of death has reached 60% – but it has remained stable beyond this period

"[The] The Gompertz model does not seem not exceed our estimated plateau beyond the age of 105, "write the researchers in the study.In addition, the data suggest that mortality rates actually decline after 105, but slightly, among those born in the same year. "

They continue:" The increasing number of people with exceptional longevity and the fact that their mortality Beyond 105, the decline of cohorts [those born in the same year] – lowering the mortality plateau or postponing the age when it appears – strongly suggests that longevity continues to increase over time and that a limit, if any, has not been reached.Our results contribute to a recently revived debate about the existence of a maximum lifespan It is fixed for humans, underwriting the doubt that any limit is still in sight. "

The oldest known person ever lived at the age of 122, but the reason we did not see anyone living at 140, 200, or beyond, was that 60% chance of dying each year, all but guaranteeing our possible disappearance – at least, according to this document.

This analysis was purely The authors did not provide any tangible or significant explanation of the observed mortality plateau, aside from the suggestion that structural factors (for example, improved health care for the elderly) and evolving factors (eg related genetic factors) are likely to be at stake. Brandon Milholland, an aging researcher from the College's Department of Genetics of Medicine Albert Einstein who was not involved in the new study, said the new document is interesting, but he believes that it is only a small piece of a break-up much larger head [1 9659005] "It is based on seven years of data in one country, and most data apply for ages 105 to 108," Milholland told Gizmodo. "I would say that this document does not tell us much about the mortality of the over-indebted, it is also questionable if the results are generalizable to other countries."

The finding that the late mortality differs from the law of Gompertz, he said, is not particularly surprising.

"For most of adult life, mortality doubles every eight years or so," said Milholland. "This document makes sense that dubbing can not continue indefinitely, if the mortality is 60%, it can not double to 120%, which is mathematically impossible." However, this paper models mortality at the end of life as being suddenly stopped and remaining completely flat.It is very implausible. "

Milholland said that a leveling is understandable, but that does not mean that he has to stay flat .

"In fact, it seems rather far-fetched that after an exponential increase, the chance of dying should suddenly stop," he said. "It is possible to imagine any number of curves that continue to increase without exceeding 100%." ​​I am disappointed that a false dichotomy has been presented between the Gompertz law and a complete plateau. This review is not intended to distinguish this particular document and, to my knowledge, no one has examined late mortality with a more sophisticated model, however, I do not consider that the evidence of a plateau presented in this document is particularly strong. "

S. Jay Olshansky, a professor at the School of Public Health at the University of Illinois at Chicago, also has serious doubts about the new document, although he said the authors have does a great job creating a new set of data to evaluate. 19659004] "The key element, however, is that researchers have had to work very hard to create such a dataset because so few people live to old age," Olshansky told Gizmodo. . "Why are you asking? Because there is a limit to human longevity that is fundamentally influenced by our basic biology and the conception of the body inherited from our ancestors, so when people have gone beyond the limits of human life, we are not the only ones in the world. At the age of 105, they have approached the maximum that humans can live. "

The observation that extreme death rates are aging around 105, or continue to increase, It does not matter, he says, because by the time people reach these ages, at least half of them disappear every year

– people survive at the age of 110 out of billions What difference does it make if 50 or 60 die before their next birthday? Human bodies are not intended for long-term use, and when we manage to make them work by the end of a century, many Age-related diseases accumulate, "Ols said hansky. "Debating mortality rates of a small number of people at extreme ages, and concluding about the longevity of humans in general, is tantamount to describing the average running speed for running a mile to all humanity by examining the world records running established by Olympic athletes. "

" There is simply not enough people who survive after the age of 110 to generate reliable mortality rates. Why? Because there is a limit to the length of life. How obvious is it? "

Olshansky said that the observation that mortality rates could stabilize at a later age is not unexpected, but there is evidence to the contrary.

" Remember these people have been highly selected by the time, so the only people who can live so long have had to win the genetic lottery at birth, "he said." The rest of us do not have the chance to win the genetic lottery at birth, "he said. have almost no chance of living so long. The conclusion that there is no limit to life does not stem from these data. The fact that there is a limit to life should come from the fact that it is so difficult to find enough people in old age to generate reliable mortality rates. For this dataset, there is simply not enough people who survive after the age of 110 to generate reliable mortality rates. Why? Because there is a limit to the length of life. How obvious is it? "

With regard to Olshansky, these results should not affect the way we study aging and develop therapeutic interventions." Instead, he said that scientists should try to understand why people under the age of 100 are dying and find ways to slow their aging. "I'm less interested in the tails of the cast – except to understand what makes them so unique – I m 39 much more interested in the rest of humanity who will not live so long, "he said.

But not all scientists see it that way.

Siegfried Hekimi, professor of Biology at McGill University in Montreal, said that the conclusion of the study, according to which age-specific mortality does not increase after a certain age, is reasonable.

"This conclusion is very firm for all of e data that is examined, "Hekimi told Gizmodo. "And the data set is very good.If age-specific mortality does not increase anymore after a certain age, then some people can reach a very old age."

No matter where the & this is the paper, the next steps for scientists are reasonably clear: better data, and do not rely solely on statistics and demographics. Moreover, the only way to find the true answer to this mystery will be to dive into biology itself.

[ Science]