Does human longevity have a biological limit? The subject always divides

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Does human longevity have a biological limit? The subject still divides

Sister André was the dean of humanity since April 25, 2022.

While the dean of humanity , French sister André, died last week at 118, the topic of human longevity continues to divide researchers: Is our existence biologically limited or can it grow indefinitely?

< p class="e-p">At the end of the 18th century, Buffon estimated that a healthy person who suffered no accident or suffered from any disease could live a maximum of one hundred years.

Centenarians were very rare then. But with the improvement of living conditions and advances in medicine, assumptions about the limit of human life have gradually been pushed back.

In 1995, a new milestone was reached when Frenchwoman Jeanne Calment celebrated her 120th birthday. Died in 1997 at the age of 122, she remains to this day the person having lived the longest in the history of humanity whose marital status has been verified.

Jeanne Calment shortly before her birthday in February 1996.

More generally, since 1950, the number of French centenarians has increased tenfold every ten years to reach 27,500 at the end of 2021, according to the National Institute for Demographic Studies (INED).

They, and especially them, could be seven times more numerous in 2060. A multiplication coupled with the appearance since the 1980s of supercentenarians, aged 110 or more, which raises the question of the limit of the human longevity.

But the subject divides researchers. On the one hand, there are those who defend the idea that lifespan is limited by biological constraints.

At present, Canada has over 9,500 centenarians, an increase of 16% from 2016. Centenarians represent 0.03% of the Canadian population.

In an article published in Nature< /em>in 2016, geneticists showed that there had been no improvement in human longevity since the late 1990s.

S' x27; based on demographic data, they found that since the death of Jeanne Calment, the maximum human lifespan has decreased, even though there are more and more old people in the world. They conclude that human lifespan has a natural limit and that longevity is limited to around 115 years, demographer and centenarian specialist Jean-Marie Robine told AFP.

But this hypothesis is partly disputed by many demographers, he continues.

Thus, a study published in 2018 in Science supports the x27;idea that the mortality rate increases with age, but slows down from age 85 and peaks at 50% or 60% per year around age 107.

With this theory, if we have 12 people aged 110, 6 will survive at 111 years, 3 at 112 years, etc., decrypts Mr. Robine. But with 100 centenarians, there will be 50 at 111, 25 at 112, etc. Thanks to a volume effect, there are no longer fixed limits to longevity.

In a French study to be published in 2023, the INSERM demographer and his team show, however, that mortality rather continues to increase beyond 105 years.

An argument in favor of a biological limit at existence? Mr. Robin does not go that far.

We will continue to make discoveries, as there have always been, and gradually improve the state of health of the elderly, he anticipates.

Like him, many researchers prefer to remain very cautious: there is currently no definitive answer, France Meslé, research director at INED, told AFP. Even if they are increasing, the numbers of generations reaching very old ages are still quite small and we still cannot make significant statistical estimates, she argues.

In summary, we will have to wait until we have enough supercentenarians to be able to draw reliable conclusions.

Finally, some specialists in aging, such as the geriatrician Éric Boulanger, do not rule out other factors coming into play in the years to come. He suggests to AFP that genetic manipulation could push back the age of death, for some, to 140 or 150 years.

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