Human evolution Intelligent Design

Does human mortality really slow down between 105 yrs and 110 years?

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Remember the story earlier this year about the anomalous plateau found in the human lifespan, such that “after the age of 105, human mortality seems to hit a plateau. That is, you aren’t any more likely to die at 110 than at 105”?

It’s been challenged by a study in PLOS Biology which suggests that the finding may be an artifact of errors in record-keeping re births and deaths:

Age-recording errors can theoretically lead to plateaus in very old ages, Newman and other demographers have suggested, because at those extreme ages, most people with age underestimation errors have already died, meaning that people with age overestimation errors—whose mortality rates correspond to their true, younger ages—make up a greater and greater proportion of the data and drag down apparent mortality rates.

But the original authors stand by their data:

In a response published in the same issue as Newman’s comment, Wachter argues that Newman’s model predicts a “wildly implausible” rate of age misreporting.

“If we tried to apply Saul Newman’s model to our data, that would be claiming that every one of the 118 people we observe over the age of 110 was really born 10 years after the entry shown in their birth registration. And that’s just absurd,” Wachter tells The Scientist. He adds that in his dataset, there are birth and death records for all of the 110-year-olds and that, combined with the particular way births were recorded at the time (in handwritten books kept by village officials, one volume per year), virtually eliminates the possibility of errors. Ashley P. Taylor, “New Study Questions Whether Death Rate Levels Off in Old Age” at The Scientist

The fact that more people are living longer means that we may get lots more data in coming decades, from periods when error was simply less likely. We shall see.

Several organisms, including humans, display a deceleration in mortality rates at advanced ages. This mortality deceleration is sufficiently rapid to allow late-life mortality to plateau in old age in several species, causing the apparent cessation of biological ageing. Here, it is shown that late-life mortality deceleration (LLMD) and late-life plateaus are caused by common demographic errors. Age estimation and cohort blending errors introduced at rates below 1 in 10,000 are sufficient to cause LLMD and plateaus. In humans, observed error rates of birth and death registration predict the magnitude of LLMD. Correction for these sources of demographic error using a mixed linear model eliminates LLMD and late-life mortality plateaus (LLMPs) without recourse to biological or evolutionary models. These results suggest models developed to explain LLMD have been fitted to an error distribution, that ageing does not slow or stop during old age in humans, and that there is a finite limit to human longevity. Abstract: (open access) More.

See also: Anomaly: Human mortality hits a plateau after 105 years of age


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