A Counterpoint to the Concept of the Late Life Mortality Plateau
Last week I posted on what seems to be the strikingly different nature of aging at very advanced ages. For example, there is what is known as the mortality plateau in very late life, a period in which mortality rates stop increasing. This has been studied in flies, and there is a small amount of evidence that suggests it might also exist in humans. But I thought I'd point you in the opposite direction today. The research partnership of Leonid Gavrilov and Natalia Gavrilova published a study on mortality at advanced ages not so very long ago, and their data suggests that there is no mortality plateau for humans. The link below is a PDF version of the paper:
Accurate estimates of mortality at advanced ages are essential to improving forecasts of mortality and the population size of the oldest old age group. However, estimation of hazard rates at extremely old ages poses serious challenges to researchers: (1) The observed mortality deceleration may be at least partially an artifact of mixing different birth cohorts with different mortality (heterogeneity effect); (2) standard assumptions of hazard rate estimates may be invalid when risk of death is extremely high at old ages and (3) ages of very old people may be exaggerated.One way of obtaining estimates of mortality at extreme ages is to pool together international records of persons surviving to extreme ages with subsequent efforts of strict age validation. This approach helps researchers to resolve the third of the above-mentioned problems but does not resolve the first two problems because of inevitable data heterogeneity when data for people belonging to different birth cohorts and countries are pooled together. In this paper we propose an alternative approach, which gives an opportunity to resolve the first two problems by compiling data for more homogeneous single-year birth cohorts with hazard rates measured at narrow (monthly) age intervals.
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Study of several single-year extinct birth cohorts shows that mortality trajectory at advanced ages follows the Gompertz law up to the ages 102-105 years without a noticeable deceleration. Earlier reports of mortality deceleration (deviation of mortality from the Gompertz law) at ages below 100 appear to be artifacts of mixing together several birth cohorts with different mortality levels and using cross-sectional instead of cohort data. Age exaggeration and crude assumptions applied to mortality estimates at advanced ages may also contribute to mortality underestimation at very advanced ages.
All the more reason to work harder on the development of rejuvenation biotechnology, capable of repairing the damage of aging. Time waits for no one.