New study suggests life expectancy gains towards 100 are slowing

It’s easy to think that, after the sharp rise in life expectancy over the past century or so, routinely reaching 100 will eventually become the norm. Fresh research, however, indicates that the long-running surge is beginning to lose momentum.

What the researchers analysed

An international group of scientists examined population statistics from 23 high-income, low-mortality countries throughout the 20th century. They paired historical records with six separate forecasting models, focusing mainly on people born between 1939 and 2000.

Their central finding is that improvements in life expectancy are already decelerating markedly, and the slowdown is expected to persist for the foreseeable future. Life expectancy is still projected to creep upwards, but the pace is set to be roughly half of what it was before.

Taken together, that means societies - and individuals - may need to recalibrate expectations about how long people are likely to live.

"We forecast that those born in 1980 will not live to be 100 on average, and none of the cohorts in our study will reach this milestone," says demographer José Andrade, from the Max Planck Institute for Demographic Research in Germany.

"This decline is largely due to the fact that past surges in longevity were driven by remarkable improvements in survival at very young ages."

Why life expectancy is increasing more slowly

The researchers point to the major shift in infant mortality as central to their results. In wealthier countries, survival at the youngest ages has improved dramatically - helped by advances in medicine and public hygiene, among other changes - leaving far less scope for additional gains than in the past.

When the team reviewed the historical data, they found that between 1900 and 1938, life expectancy rose by about 5.5 months per generation. Among those born from 1939 to 2000, the increase eased to roughly 2.5 to 3.5 months per generation - a clear drop in the rate of progress.

Life expectancy differs widely depending on location and many other influences, but in developed nations it is now sitting at around the 80-year mark. The analysis suggests that figure is not likely to climb rapidly for quite some time.

"In the absence of any major breakthroughs that significantly extend human life, life expectancy would still not match the rapid increases seen in the early 20th century even if adult survival improved twice as fast as we predict," says applied population economist Héctor Pifarré i Arolas, from the University of Wisconsin-Madison.

What this means for healthcare, pensions, and research

Understanding life expectancy has practical value in many settings - from shaping national healthcare planning to deciding how much to pay into a pension. At the individual level, we also know lifespan is affected by a wide range of factors, from how much exercise someone gets to how near they live to the coast.

What this study highlights is how those influences add up at population scale - and how the slowing trend may help identify where further research should be prioritised, or where healthcare could improve, in order to support longer and healthier lives.

"The unprecedented increase in life expectancy we achieved in the first half of the 20th century appears to be a phenomenon we are unlikely to achieve again in the foreseeable future," says Arolas.

The research has been published in PNAS.