Demography

The decline in longevity: why those born after 1939 are unlikely to live to be 100 years old

International study highlights slowdown in life expectancy growth for generations born after 1939

by Francesca Cerati

9 September 2025

3' min read

Translated by AI

Versione italiana

Key points

Growth rate halved
Children of 2020 and the burden of climate
Two strands intertwining

3' min read

Translated by AI

Versione italiana

Humanity may have passed its 'longevity peak'. This is the conclusion reached by a large international study coordinated by José Andrade, demographer at the Max Planck Institute for Demographic Research, published in Pnas.

For more than half a century, humanity has been experiencing a longevity revolution. Between 1900 and 1938, life expectancy in rich countries grew at an unprecedented rate: six months longer for every year of birth, rising from 62 to 80 years in just a few decades. A goal that seemed destined to propel more and more people beyond the symbolic threshold of one hundred years. But no. The recently published study shows that that progress is now behind us.

The growth rate has halved

Analysing data from 23 industrialised countries and comparing different forecasting techniques, the researchers found that, for cohorts born after 1939, the rate of growth in life expectancy has more than halved: only 2-3 months more for each year of birth. This means that those born in 1980, for example, will not reach the age of 100 on average, and none of the generations observed in the study will surpass that mark.

The main reason lies in the different origins of longevity gains. In the early 20th century, the drastic reduction in infant mortality thanks to vaccinations, antibiotics, hygiene and better housing conditions had freed up huge margins for growth. Today, on the contrary, those margins are almost exhausted: mortality in the first years of life is already minimal and possible advances in the survival of the elderly, while important, do not have the same driving force.

"The unprecedented increase in life expectancy achieved in the first half of the 20th century is unlikely to be repeated," the authors explain. And even if innovative treatments capable of slowing down ageing arrive in the coming decades, they will not be enough to restore the dizzying pace of the past.

The study emphasises that this is not just an academic issue. Longevity predictions influence crucial policies: pensions, healthcare systems, social cohesion. If life spans become shorter than expected, both governments and citizens will have to recalibrate expectations, savings and long-term planning.

The Children of 2020 and the Burden of Climate

Last May, another study - published in Nature and led by researcher Luke Grant - raised a parallel alarm: children born in 2020 will be exposed to an unprecedented number of extreme weather events during their lifetime.

Using climate and demographic models, scientists have calculated that even if global warming were contained within 1.5 °C, more than half of those born in 2020 would experience unprecedented heat waves. With an increase of 3.5 °C, the percentage would rise to 92%.

It is not just heat: droughts, fires, floods and crop failures will affect hundreds of millions of people. And the poorest communities, with the least capacity to adapt, will be the most exposed. The study speaks explicitly of an 'intergenerational injustice': those born in the 21st century will suffer the greatest impacts despite having contributed the least to climate change emissions.

Two threads intertwining

At first glance, the two studies seem to move on different planes: on the one hand the biological-demographic dynamics of longevity, on the other the environmental pressure on lifestyles. But put together they tell the same story: the future of the new generations could be shorter and harder.

The last century had deluded us that the life expectancy curve was destined to grow without limit. Today, however, it turns out that that progress is slowing down, while at the same time young cohorts face growing climate risks that can affect health, the economy and social stability.

Two forces - the erosion of longevity gains and exposure to extreme events - converge, challenging the idea of an automatically better future than the past.