For more than a century rising life expectancy has been one of humanity’s most remarkable achievements. Advances in medicine public health and social development steadily pushed survival rates upward leading some demographers to speculate that living to 100 would one day become commonplace. However a new study published in Proceedings of the National Academy of Sciences suggests this expectation may be overly optimistic.
Researchers José Andrade Carlo Giovanni Camarda and Héctor Pifarré i Arolas analyzed mortality data across 23 high-income countries using multiple forecasting methods. Their results indicate that the pace of longevity gains measured by cohort life expectancy is slowing dramatically. Individuals born between 1939 and 2000 are unlikely to experience the same linear improvements as previous generations with none of these cohorts projected to reach a life expectancy of 100 years.
Historically longevity increased at a steady rate of about 0.46 years per birth cohort between 1900 and 1938. Extrapolating that trajectory would suggest reaching a cohort life expectancy of 100 should have been achievable by those born in the 1980s. Instead the new study finds that improvements have slowed by 37% to 52% depending on the method used. Forecasts indicate gains closer to 0.22–0.29 years per cohort significantly below the historical pace.
This slowdown is not limited to a single country or an outlier population. Across all nations studied and under every forecasting approach the trend remains consistent: longevity is no longer rising as quickly as in the past.
The deceleration is primarily driven by stalled progress in reducing mortality at very young ages. For much of the 20th century declining infant and child mortality accounted for the majority of life expectancy gains. That trend has largely plateaued.
According to the researchers more than half of the deceleration is linked to mortality trends under age five while two-thirds is explained by trends under age twenty. This means the historical engine of life expectancy growth—safeguarding children from early death—has reached diminishing returns.
Even if dramatic medical breakthroughs occur the exhaustion of these early-age gains cannot be fully offset by improvements at older ages. The study simulated scenarios where mortality reductions doubled across all age groups. Even under such optimistic conditions the forecast still showed slower growth than in the first half of the 20th century.
The findings challenge both scientific assumptions and public expectations. For years demographers debated whether human life expectancy would continue rising indefinitely or eventually hit a biological ceiling. The new evidence suggests that even if no strict biological limit exists social and medical factors are failing to sustain previous gains.
This has major implications for health policy pensions and aging societies. If the life expectancy of currently living generations falls short of the once-expected century mark governments and institutions will need to reassess long-term planning for retirement healthcare and social support systems.
Uncertainty remains. As with all forecasting new epidemics lifestyle changes or radical advances in biotechnology could alter the trajectory. However the authors stress that the observed slowdown is not speculative—it is already present in the data for living cohorts. While future innovations may help extend longevity at older ages the study concludes that the dream of a routine life expectancy of 100 years remains improbable.
References
Andrade J Camarda CG & Pifarré i Arolas H (2025). Cohort mortality forecasts indicate signs of deceleration in life expectancy gains. Proceedings of the National Academy of Sciences 122(35) e2519179122.
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