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Since 1900, the average life expectancy in the world has more than doubled, thanks to the improvement of public health, sanitation and food supply. But a new study of long-term Italians indicates that we have not yet reached the upper limit of human longevity. "19659002" There is a fixed biological limit, we are not close to it, "says Elisabetta Barbi, demographer at the University of Rome Dr. Barbi and colleagues published their research Thursday in the journal Science.
The current record for the longest human life was established 21 years ago, when Jeanne Calment, a French, died at the age of 122 Nobody has aged since – as far as scientists know
In 2016, a team of scientists from the Albert Einstein College of Medicine in the Bronx boldly asserted that Ms. Calment was even more aberrant than she seemed to be.They claimed that humans reached a fixed life limit, which they estimated to be about 115 years old.
A certain number of critics blasted this research. "The data set was very poor and the statistics were very imperfect, "said Siegfried Hekimi, a biologist at McGill University
. All those who study the limits of longevity face two major statistical challenges.
There are not many people who live until old age, and people of that time often lose track of how long they have lived. "At these ages, the problem is to make sure that age is real," said Dr. Barbi.
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Dr. Barbi and his colleagues scrutinized the records of Italy to find all citizens who reached the age of 105 years between 2009 and 2015. To validate their age, the researchers found their birth certificates.
The team was found with a database of 3836 Italian elderly people. The researchers found the death certificates of those who died during the study period and determined the rate at which various age groups were dying.
It has long been known that the mortality rate begins at a young age and declines during the first years of life. He climbs again among the people in his thirties, and finally skyrockets among the septuagenarians and the eighties.
If the mortality rate increased exponentially at an older age, then the human life span would really have the kind of limit proposed by the Einstein team in 2016.
The researchers also found that people born later have a mortality rate slightly lower than 105. "The plateau is sinking with time," said Kenneth W. Wachter, a demographer at the University of Ottawa. University of California, Berkeley, who co-authored the new study. "Mortality improvements even extend to these extreme ages."
"We do not yet approach a maximum life span for humans," he added.
Brandon Milholland, a co-author of the human life study, questioned the new document. The research, he noted, was limited to only seven years in one country.
"You reduce yourself to a narrow slice of humanity," he said.
Milholland also questioned how the team analyzed his data. They only looked at two possibilities: that the death rate continued its exponential rise, or that it turned into a flat plateau.
The truth might be somewhere in between, he said, "It seems rather far-fetched that after increasing exponentially, the chance of dying should suddenly stop."
Dr. Hekimi, on the other hand, praised the study for the quality of his data and called his findings, "very interesting and surprising."
The new research does not explain why mortality rates flatten in the older of the old. One possibility is that some people have genes that make them more fragile than others. Fragile people die earlier than the most resilient, leaving behind a pool of difficult older people.
But Dr. Hekimi speculated that there could be other factors involved.
Throughout our lives, our cells are damaged. We only manage to partially repair them, and over time our bodies become weak.
It is possible that at the cellular level, very old people simply live at a slower pace. As a result, they accumulate less damage in their cells than their bodies can repair.
"It's a reasonable theory for which there is no evidence," Dr. Hekimi said. "But we can find out where there is."
A flat mortality rate does not mean that centenarians have found a fountain of youth. From one year to the next, the new study suggests that they are still far more likely to die than someone in the 90s.
The exact duration of Centennial life can be simply a roll of dice each year.
Even if it turns out to be the case, the age of Jeanne Calment will not be easily matched, said Tom Kirkwood, deputy dean of aging at Newcastle University, who said: Was not involved in this new study
. As records are successively broken, it becomes harder to break, "he said.
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