After more than a century of steady progress, new research warns that the world’s life expectancy explosion is slowing, largely because improvements in early-life mortality have already been achieved.
Study: Cohort mortality projections show signs of slowing life expectancy gains. Image credit: puyalroyo/Shutterstock.com
The rate of increase in life expectancy in high-income countries may slow over time, particularly due to the slower rate of improvement in mortality at very young ages, according to a new study published in PNAS.
Steady gains in uncertainty
Advances in public health, medical science, and socioeconomic structure have significantly increased life expectancy in high-income countries over the past century. However, it has been a matter of ongoing debate whether this upward trend will continue in the future or slow down over time.
Many studies estimating human lifespan have considered a period life expectancy approach, which is a composite measure that reflects the average risk of mortality experienced within a given calendar year. This approach can help assess adverse mortality trends, but cannot provide definitive evidence for longevity trends.
The cohort life expectancy approach, on the other hand, captures the actual survival experience of a specific group of people born in the same period, offering a direct measure of longevity.
To predict the near-future trend of human longevity, researchers from the Max Planck Institute for Demographic Research, INED, and the University of Wisconsin-Madison recently estimated life expectancy for generations born between 1939 and 2000 in high-income countries using multiple mortality prediction models.
Monitoring life expectancy trends
The researchers estimated cohort life expectancy for the currently living generations in 23 high-income, low-mortality countries using six different models that predicted age-specific mortality rates. Specifically, the researchers focused on generations born between 1939 and 2000, using data from the Human Mortality Database.
In addition, they conducted an age decomposition analysis (which quantifies the contribution of different age groups to changes in cohort life expectancy over time) to identify the main factors contributing to predicted trends in cohort life expectancy.
Gains in life expectancy have slowed
The study’s findings across all forecast models revealed a slowdown in life expectancy growth among generations born between 1939 and 2000.
In terms of past trends in longevity, the study reported an average rate of improvement of about 0.46 years per birth cohort between 1900 and 1938, meaning that each successive generation during that period lived longer than the previous one. That roughly equates to life expectancy rising from about 62 years for those born in 1900 to about 80 years for those born in 1938, though the paper doesn’t report those exact figures.
Such a dramatic improvement in life expectancy in a few years appeared to decline by 37% to 52% for generations born between 1939 and 2000, depending on the methods used for the forecast. Under an optimistic scenario where the previously observed steady improvement in life expectancy remains unchanged, people born in 1980 could expect to reach the milestone of a 100-year life expectancy cohort.
However, the current findings showed a different scenario where none of the generations analyzed in the study are expected to achieve this milestone.
The rapid decline in the infant mortality rate in the early 20th century, which was due to advances in medical science, improvements in hygiene, and higher living standards, was found to be a major contributor to the significant increase in life expectancy. In the late 20’su century, infant and child mortality rates were already extremely low, leading to a slower rate of improvement in mortality at very young ages. This pattern is closely related to the recent slowdown in life expectancy growth.
According to the study’s findings, more than half of the projected slowdown in life expectancy is attributable to mortality trends among those under 5 years of age. At the same time, more than two-thirds is explained by mortality trends in people under 20 years of age.
As discussed by the researchers, improving mortality in middle age can lead to significant gains in life expectancy. Similarly, advances in clinical practices that specifically address the underlying causes of age-related mortality, as well as improvements in behavioral risk factors, may significantly delay the onset of aging in humans. However, the current findings suggest that, at least for currently living generations, even significant improvements in the mortality rate are unlikely to reverse the projected slowdown in life expectancy.
Existing research highlights the decline in menstrual life expectancy in the United States and other developed countries, reflecting deeper economic and social factors that underscore the complex interplay between social conditions and health outcomes.
The findings of the current study suggest that this decline is not only a seasonal but also a generational phenomenon, which may be influenced by a combination of biological and social determinants. Collectively, these findings point to a broader decline in the growth rate of human longevity.
Policy and planning reform
The study’s findings provide essential insights for policymakers preparing for the future. However, it is worth noting that unforeseen or unexpected events, such as future pandemics or epidemics, dramatic changes in social or economic structure, or medical breakthroughs, can significantly alter projected mortality trends as well as the rate of increase in life expectancy.
Since the study focuses on populations rather than individuals, the observed long-term decline in life expectancy growth may affect people’s approach to saving, retirement and long-term care. While the authors emphasize broader policy implications, such as the need for governments to adapt social and health systems, both governments and individuals may need to adjust their expectations and plans for the coming decades.
