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Longevity Aging

Human Lifespan Evidence Now Being Challenged

3 months, 3 weeks ago

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Posted on Jun 30, 2017, 2 a.m.

Numerous medical researchers have publicly criticized a 2016 paper suggesting that people can live to a maximum of 115 years.

It has long been thought that human beings can live to a maximum of about 115 years. However, the limited amount of evidence for such a limit to human lifespan is now being contested. Five groups of medical researchers have publicly criticized a 2016 paper in Nature that suggests people can live to a maximum of 115 years.

About the Supposed Maximum Human Lifespan

The above-referenced paper made the headlines as its authors claimed that human longevity is inherently limited. The claim catalyzed a spirited debate between scientists as plenty of people were not convinced by the paper's alleged evidence for a lifespan maximum of 115 years. It all centers on a 2016 study led by Albert Einstein College of Medicine molecular geneticist Jan Vijg.

Vijg's research group delved into worldwide demographic data across the past century. The group showed that since the mid-1990s, the peak age leveled off at 115 years. These results prompted Vijg's group to claim human beings have a natural age limit of 115. They calculated the odds of an individual surviving beyond the age of 125 was less than 1 in 10,000.

The Response

Five groups of leading biological researchers responded to the paper published in Nature with a collection of formal rebuttals. These rebuttals were published on June 28 in Nature Communications Arising. The rebuttals state Vijg's claim of an inherent limit to human lifespan is flawed. They argue it is an extreme claim that should be deeply scrutinized to verify or prove false. They argue an alternate explanation exists: the maximum age of human beings increases as time progresses. What looks to be an extension of lifespan is really just a finding derived by performing a superficial analysis of statistics that were used in an inappropriate manner.

Nick Brown, a University of Groningen PhD student and co-author of one of the rebuttals, states the primary problem with Vijg's study is that he used a dataset split at 1995 after scanning the data and observing a supposed plateau at that peak age in that year. They then proceeded to test the same data to determine if this was, in fact, the case. Brown argues Vijg's team thought they had identified a pattern and proceeded to create a theory to explain the pattern. The data matched the theory simply because it was generated from that exact data. Brown believes this is a flawed means of practicing science. Brown is also adamant that the research team's analysis of lifespan is rife with problems. They included the oldest individual to die in any given year, creating a tiny sample with an abundance of randomness. The data was much too limited.

McGill University biologist Siegfried Hekimi re-analyzed the data in question. He found it was consistent with several different trajectories for lifespan including one without a plateau and one with a plateau at an advanced age. The bottom line is the data is consistent with plenty of other trends meaning that there is no limit to lifespan at this point in time. Additional rebuttals echoed these sentiments.

The Expectation of a Backpedal

The scientific community expected Vijg to take back his claim of a limit to human lifespan. However, the rebuttals provided by fellow scientists did not prove convincing to him. Vijg stands by his research team's results, arguing that the scientific community must let the data speak. He claims his group tested two independent databases. Several outside experts agree with Vijg. The mere fact that Vijg's claims are criticized does not invalidate his claim, yet it does open the door to further questioning of it.

N.J.L. Brown et al., “Contesting the evidence for limited human Lifespan,” Nature Communications Arising, doi:10.1038/nature22784, 2017.

J. de Beer et al., “Maximum human lifespan may increase to 125 years,” Nature Communications Arising, doi:10.1038/nature22792, 2017.

M.P. Rozing et al., “Is there evidence for a limit to human lifespan?” Nature Communications Arising, doi: 10.1038/nature22788, 2017.

B.G. Hughes & S. Hekimi, “Many possible maximum lifespan trajectories,” Nature Communications Arising, doi:10.1038/nature22786, 2017.

A. Lenart & J.W. Vaupel, “Questionable evidence for a limit to human lifespan, Nature Communications Arising, doi:10.1038/nature22790, 2017.

http://www.the-scientist.com/?articles.view/articleNo/49758/title/Evidence-for-Human-Lifespan-Limit-Contested/

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