[Rapid increase in maximal country specific life expectancy across cohorts].
Level 3 - non-randomized controlled study
Level 3 by design analogy (longitudinal demographic cohort analysis and mortality forecasting).
What was done
The authors analyzed historical trends in best-practice (maximum country-level) cohort and period life expectancy across birth cohorts from 1870 to 1950. Data were obtained from the Human Mortality Database covering 24 developed countries from 1870 to 2008. To project complete lifespans for non-extinct cohorts, the Lee-Carter mortality model was used to extrapolate mortality rates through the year 2050.
What was found
Best-practice cohort life expectancy increased from 53.7 years for the 1870 birth cohort to 83.8 years for the 1950 birth cohort, averaging an annual increase of 0.43 years. In comparison, period life expectancy over the same interval rose at 0.28 years per year. The gap between period and cohort life expectancy widened from 1.2 years in 1870 to 10.3 years in 1950. For cohorts born between 1920 and 1950, the majority of the gained lifetime is projected to be spent at ages 65 and older.
Why it matters
Period life expectancy substantially underestimates the actual lifespan of individuals living through eras of sustained mortality decline. Demonstrating that maximal cohort life expectancy grew faster than period metrics highlights the shifting age distribution of human lifetimes toward older ages.
Limits
The dataset was restricted to 24 developed countries, limiting generalizability to other populations. Estimates for non-extinct cohorts born up to 1950 rely on Lee-Carter model extrapolations through 2050, which assume past mortality trajectories persist and cannot anticipate future demographic or medical shocks. Healthspan and morbidity outcomes were not analyzed.
Cited by
- supports On average, scientific and medical progress currently extends human life expectancy by approximately one quarter of a year for every year lived.