Rectangularization of the survival curve reconsidered: The maximum inner rectangle approach

Area of Science:

• Demography
• Public Health
• Gerontology

Background:

• The rectangularization of the survival curve is a key framework in mortality research.
• Assumptions of this framework are becoming obsolete in high-income countries due to reduced mortality among the oldest old.
• Recent mortality changes necessitate a refinement of existing analytical frameworks.

Purpose of the Study:

• To propose a refined concept for survival curve rectangularization.
• To introduce the 'maximum inner rectangle approach' (MIRA) to adjust for recent and future mortality changes.
• To analyze outer and inner rectangularization processes and their implications for lifespan and mortality.

Main Methods:

• Development of the 'maximum inner rectangle approach' (MIRA).
• Distinguishing between outer rectangularization (mean vs. maximum lifespan) and inner rectangularization (lifespan equality vs. mean lifespan).
• Empirical application of MIRA to historical and recent mortality data.

Main Results:

• Both outer and inner rectangularization have generally increased since 1850.
• Inner rectangularization shows country-specific patterns following declines in old-age mortality.
• A shift from reducing premature deaths to extending the premature age range is observed, potentially indicating limits.

Conclusions:

• The MIRA provides a refined framework for understanding mortality changes.
• Recent trends suggest a transition in the focus of mortality reduction strategies.
• Further research is needed to explore the implications of these shifts for population health and longevity.