The question of the human mortality plateau: Contrasting insights by longevity pioneers

Linh Hoang Khanh Dang; Carlo Giovanni Camarda; France Meslé; Nadine Ouellette; Jean-Marie Robine; Jacques Vallin

Volume 48 - Article 11 | Pages 321–338

The question of the human mortality plateau: Contrasting insights by longevity pioneers

By Linh Hoang Khanh Dang, Carlo Giovanni Camarda, France Meslé, Nadine Ouellette, Jean-Marie Robine, Jacques Vallin

Date received:

19 Jan 2021

Date published:

28 Feb 2023

Word count:

3617

Keywords:

age, France, Gompertz mortality, mortality, mortality plateau, older population, parametric models, supercentenarians, survival analysis, trajectories

DOI:

10.4054/DemRes.2023.48.11

Additional Files:

demographic-research.48-11 (zip file, 45 kB)
readme.48-11 (text file, 310 Byte)

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Abstract

Background: The debate about limits to the human life span is often based on outcomes from mortality at the oldest ages among longevity pioneers. To this day, scholars disagree on the existence of a late-life plateau in human mortality. Amid various statistical analysis frameworks, the parametric proportional hazards model is a simple and valuable approach to test the presence of a plateau by assuming different baseline hazard functions on individual-level data.

Objective: We replicate and propose some improvements to the methods of Barbi et al. (2018) to explore whether death rates reach a plateau at later ages in the French population as it does for Italians in the original study.

Methods: We use a large set of exceptionally reliable data covering the most recently extinct birth cohorts, 1883–1901, where all 3,789 members who were born and died in France, were followed from age 105 onward. Individual life trajectories are modeled by a proportional hazards model with fixed covariates (gender, birth cohort) and a Gompertz baseline hazard function.

Results: In contrast with Barbi et al. (2018)’s results, our Gompertz slope parameter estimate is statistically different from zero across all model specifications, suggesting death rates continue to increase beyond 105 years old in the French population. In addition, we find no significant birth cohort effect but a significant male disadvantage in mortality after age 105.

Conclusions: Using the best data currently available, we did not find any evidence of a mortality plateau in French individuals aged 105 and older.

Contribution: The evidence for the existence of an extreme-age mortality plateau in recent Italian cohorts does not extend to recent French cohorts. Caution in generalizations is advised, and we encourage further studies on long-lived populations with high-quality data.

Author's Affiliation

Linh Hoang Khanh Dang - Institut National d'Études Démographiques (INED), France EMAIL
Carlo Giovanni Camarda - Institut National d'Études Démographiques (INED), France EMAIL
France Meslé - Institut National d'Études Démographiques (INED), France EMAIL
Nadine Ouellette - Université de Montréal, Canada EMAIL
Jean-Marie Robine - Institut National de la Santé et de la Recherche Médicale (INSERM), France EMAIL
Jacques Vallin - Institut National d'Études Démographiques (INED), France EMAIL