Actuarial Aging Rates in Human Cohorts.

Area of Science:

• Demography
• Gerontology
• Population Health

Background:

• Aging rate is a key human aging characteristic.
• Previous studies using cross-sectional data suggested stable or increasing aging rates.
• Analysis of real birth cohorts provides a more accurate understanding of aging dynamics.

Purpose of the Study:

• To analyze historical changes in actuarial aging rates within human cohorts.
• To investigate patterns of aging rate changes across different populations and birth years.
• To test the compensation effect of mortality (CEM) in human cohorts.

Main Methods:

• Utilized one-year cohort age-specific death rates from the Human Mortality Database (HMD).
• Estimated Gompertz parameters in the 50-80 year age interval for 2,294 cohorts from 76 populations.
• Analyzed historical trends in the Gompertz slope parameter for actuarial aging rate.

Main Results:

• Two distinct patterns of actuarial aging rate changes were observed across cohorts.
• Higher mortality Eastern European countries showed a continuous decline from 1910-1940 birth cohorts.
• Lower mortality countries (Western Europe, Australia, Canada, Japan, New Zealand, USA) showed initial decline followed by an increase after ~1930 birth cohorts.
• Overall, 68% of populations exhibited a decreasing trend in actuarial aging rate over time.
• Compensation effect of mortality (CEM) was confirmed in human cohorts.
• Cohort species-specific lifespan estimates aligned with previous cross-sectional data.

Conclusions:

• Actuarial aging rates in human cohorts display complex historical patterns, varying by population mortality levels.
• The study highlights the importance of cohort-based analysis over cross-sectional data for understanding aging dynamics.
• The compensation effect of mortality is a relevant factor in human aging, influencing lifespan estimates.