Is the increase in life expectancy destined to slow down in the 21st century?

The increase in life expectancy, spectacular in the last century, has slowed markedly for thirty years in the countries where it is the highest and cannot continue in the 21st century in the absence of decisive progress to slow down the effects. of old age, according to a demographic study on Monday.

Until the middle of the 19th century, life expectancy at birth fluctuated between 20 and 50 years. In the following century, advances in medicine and public health “produced a longevity revolution,” recalls the study signed in Nature Aging by the American demographer S. Jay Olshansky.

While humans previously gained an average of one year of life expectancy in one or two centuries, the gain increased to three years of life expectancy per decade during the 20th century.

But does this progression have a limit? In France, where the former dean of humanity Jeanne Calment is said to have died at age 122, life expectancy at birth in 2019 was 79.7 years for men and 85.6 for women.

As early as 1990, researchers, notably Professor Olshansky, predicted a limit to medical progress in the face of aging. Others have, on the contrary, defended the theoretical absence of a biological ceiling.

“We can no longer achieve significant gains in life expectancy based on disease reduction,” he told AFP.

By basing its demonstration on the statistics of the eight countries with the longest life expectancy at birth (Australia, South Korea, Spain, France, Italy, Japan, Sweden, Switzerland) over the period 1990-2019.

Their populations can expect to live on average 6.5 years longer if they were born in 2019 rather than in 1990. A gain much lower than that recorded over the previous period.

These results “suggest that humanity’s battle for long life is largely over,” the study concludes. Even if a majority of the world’s countries are still waiting to benefit from the advances in public health that have benefited the richest.

The fight for life expectancy is simply a victim today of the “law of diminishing returns,” explains demographer and epidemiologist Jean-Marie Robine, who did not participate in the study, to AFP.

The gains recorded in the 20th century were first and foremost the result of a drastic reduction in infant mortality. However, by reducing it “we immediately make considerable gains in life expectancy”, recalls this emeritus research director at the National Institute of Health and Medical Research (Inserm).

“And then gradually, we will begin to reduce mortality in middle age” and make gains in that of seniors after the Second World War, to the point that today “not many people die before 70 years”. Ultimately, populations benefit from a “compression of mortality” towards a higher age group. In other words, a “reduction of social inequality in the face of death”.

The remaining room for progress is even more reduced, according to the study. In the countries considered, mortality, from all causes and at all ages, would need to be reduced by around 20% for women’s life expectancy at birth to increase from 88 to 89 years.

For populations born in 2019, the chances of survival to 100 years affect only 5.1% of women and 1.8% of men.

Which makes S. Jay Olshansky say that “the door that remains open to us is that of the science of gerontology.” And that in the absence of a breakthrough in this area it would be better to favor “healthy life span than life expectancy”.

Jean-Marie Robine, for his part, notes that there remains “grit to grind” to reduce mortality between 75 and 95 years of age.

Beyond that, he is betting that if “we are blocked by the fragility of the elderly, it is not because we are today that we will be indefinitely”.

“We have never had so many laboratories and researchers, public or private, looking for solutions” to the “fragility” of elderly people, which makes them vulnerable to “extreme events”.

And therefore “the idea that we are at the end of progress is an illusion”, according to him.