The spectacular increase in life expectancy that humans have experienced during the 20th centurye century seems to be running out of steam rather than continuing its growth, say US researchers who analyzed mortality data in ten regions of the world. Their observation which is published in the journal Nature Aging indicates that humans are reaching the limits of their longevity. Unless we discover a therapy capable of slowing down biological aging. Which, for the moment, is still very far from reality.
During the 20the century, life expectancy at birth increased by around 30 years in high-income countries, largely thanks to advances in medicine and public health. A reduction in mortality was first observed at young ages, then subsequently at middle and older ages.
“It was a real revolution in longevity because life expectancy accelerated, going from an increase of one additional year per century, or even two centuries during the last two millennia, to an average of three years of life. additional per decade during the 20th centurye century,” emphasize the authors of the article.
Since the end of the 20th centurye century, many wonder if this acceleration in life expectancy will continue for a long time or if it will slow down given the limits of human biology.
In 1990, two hypotheses were therefore proposed. On the one hand, that according to which humanity is approaching the upper limit of its life expectancy in the populations with the greatest longevity, given that “the gains brought by the improvement of public health and healthcare health have been largely accomplished”, the main risk factor for mortality being biological aging against which nothing can be done.
The second “radical life extension” hypothesis, which is based on the discovery and deployment of medical technologies capable of extending life, predicts the same increase in life expectancy at birth as that observed in XXe century, an increase of 0.3 years per year (or three years per decade). According to this hypothesis, most babies born today will live to be 100 years old or older.
Life expectancy is growing less and less
Researchers from the Universities of Illinois, Hawaii, Harvard and California in Los Angeles wanted to settle the question. To do this, they measured demographic survival in eight countries whose populations had the longest life expectancy (Australia, France, Italy, Japan, South Korea, Spain, Sweden and Switzerland), as well as in Hong Kong and in the United States. They measured trends in mortality rates and life expectancy during the period from 1990 to 2019.
And they found that since 1990, the rate of improvement in life expectancy has slowed. “It has become progressively more difficult to increase life expectancy,” they write. In summary, they observed an average rate of improvement — reduction — in mortality among people aged 65 and over of 30.2% during the three decades between 1990 and 2019. They also calculated that if If this same level of improvement is repeated over the next three decades, it would result in an increase in life expectancy of only 2.5 years, which is a fraction of the three years per decade predicted by the radical extension of life.
Specifically, they noticed that only South Korea and Hong Kong experienced a three-year per decade improvement in the life expectancy of their populations. In Hong Kong, this good improvement is attributable to economic prosperity and tobacco control measures, but only between 1990 and 2000, the researchers said.
Across all populations, including that of Hong Kong, the improvement in life expectancy from 2010 to 2019 slowed compared to what was observed from 1990 to 2000. The average increase in life expectancy from 1990 to 2019 in nine of the nations studied, except the United States, was 6.5 years. The United States is one of the few documented countries that experienced lower life expectancy at the end of each decade compared to the beginning of the same decade.
The researchers also estimated that in 2019, an average of 5.1% of female babies and 1.8% of male infants in the countries studied will live to be 100 years old. The population where young children were most likely to survive to age 100 was Hong Kong, where 12.8% of women and 4.4% of men were expected to reach this ripe old age. In the United States, it is 3.1% of girls and 1.3% of boys.
The researchers point out that this hypothesis of the radical extension of life could, on the other hand, become a reality during this century in certain low- or middle-income countries.
The limits of slowing down aging
Their analysis suggests that during the 21st centurye century, survival to the age of 100 should not exceed 15% in women and 5% in men, unless we manage to develop therapies capable of significantly slowing down the biological aging process.
The National Institute on Aging’s Interventions Testing Program (ITP), which aims to identify substances that would extend lifespan in mice, has shown that “potential therapies have limited effectiveness,” the researchers say. “Of the 50 compounds they’ve tested so far, only 12 increased the lifespan of mice, but none of them by more than 15%. »
The increase in life expectancy at birth in countries with long-lived populations should not be confused with anticipated increases in the number of people reaching old age during the 21st century.e century, because the latter result from the birth booms which took place during the 20the century, as well as the improvement in the survival of very old people thanks to advances in medicine, warn researchers, who predict a large increase in the centenarian population across the globe from 2042, i.e. say 100 years after the start of the baby boom following the Second World War.
For these researchers, it is clear that “humanity’s battle to extend life has largely been accomplished.” “But this does not mean that improvements in mortality at all ages, and particularly at older ages, are no longer possible or that healthy life expectancy can no longer be improved by modifying risk factors. or the reduction of inequalities.
Given the advances being made in “geroscience,” the discipline that seeks to slow aging, there is reason to be optimistic that we will succeed in slowing down biological aging, but this will not be the case in the 21st century.e century, say the authors of the study.