Competing Effects on the Average Age of Infant Death

Area of Science:

• Demography
• Public Health
• Biostatistics

Background:

• The traditional relationship between infant mortality and life expectancy at birth (a10) has weakened in developed nations.
• Low infant mortality rates now correspond to a wide range of a10 values, indicating other factors are influencing life expectancy.
• Disparities in preterm birth rates between racial groups, such as non-Hispanic White and non-Hispanic Black mothers in the US, highlight differing impacts on a10.

Purpose of the Study:

• To investigate the competing effects of declining mortality and changes in preterm birth rates on life expectancy at birth (a10).
• To develop and validate a new approximation formula for a10 in low-mortality settings that accounts for preterm birth variations.
• To utilize linked birth and infant death data to model these demographic trends.

Main Methods:

• Analysis of linked birth and infant death cohort data for populations with differing preterm birth rates (non-Hispanic White vs. non-Hispanic Black mothers).
• Simulation modeling to demonstrate the independent effects of falling mortality and reduced preterm births on a10.
• Development of a novel approximation formula for a10 using the ratio of infant to under-five mortality as a proxy for preterm birth differences.
• Model testing and validation using data from the Human Mortality Database.

Main Results:

• Falling mortality rates were shown to decrease the life table quantity a10.
• Reductions in preterm births were demonstrated to increase a10.
• The newly proposed approximation formula for a10 showed superior performance compared to existing models in low-mortality contexts.
• The model effectively incorporates differences in preterm birth rates.

Conclusions:

• The breakdown in the infant mortality-a10 relationship necessitates updated demographic modeling.
• Preterm birth rates significantly influence life expectancy at birth (a10) independently of overall infant mortality.
• The new approximation formula offers a more accurate method for estimating a10 in contemporary low-mortality populations, particularly when accounting for preterm birth variations.