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Thursday, June 29, 2017

Update to "What If We Can't Possibly Live Past Age 122"

Two days ago I blogged about the possibility (a distant one, to be sure) that humans might live to be 1,000 years old. Yesterday, I blogged about a study published a few months ago in Nature suggesting that we have hit the limit of human lifespan and it is 122. Eddie Hunsinger quickly emailed me to point out that I had suggested in yesterday's blog that Jim Vaupel and Jay Olshansky both thought that the limit of human lifespan was 122, but in fact only Vaupel had made that assertion. Eddie was absolutely correct and so I am updating my thoughts here to get them in line with what the article in Retraction Watch actually said:
Jim Vaupel, a gerontologist at the Max Planck Institute for Demographic Research in Rostock, Germany and one of the authors of one of the BCAs, was one of the harshest critics. He told Retraction Watch: The “findings” stem from their naive use of inappropriate data…The balance of evidence suggests that if there is a limit, it is above 120, perhaps much above and perhaps there is not a limit at all. Whether or not there is a looming limit is an important scientific question. Because they used weak statistical methods to analyze inappropriate data, they contribute nothing useful to deeper understanding of human life expectancy and human lifespan.
Jay Olshansky, of the University of Illinois at Chicago — who both reviewed the original article and wrote a “News and Views” piece accompanying it, told Retraction Watch that the authors of the rebuttals are “missing the point:” The rebuttals are mostly focused on slightly different ways of looking at the same limited data; basically, if you tilt your head a little to the left or right and look at the same old age mortality/survival statistics for all humans, you might come to slightly different conclusions. They quibble about how to deal with the mathematics of small numbers at extreme old age, and they fail to realize the obvious, staring them right in the face: the number of people surviving to extreme old age is so small because there is a biologically based limit to life operating on our species, and what they’re quibbling about is the byproduct of the very phenomenon they think does not exist.
Olshansky's conclusion is OK if we are seeking evidence only from the past record of ages at death. But, there are two problems with that, one of which was noted by the Retraction Watch article:
Vaupel also...told Retraction Watch that maximum age at death was even the wrong statistic — instead, the authors should have been looking at the oldest person alive in a given year: In many years the maximum lifespan attained in that year is greater than the maximum age at death–because someone is still alive at an age greater than the maximum age at death. An analysis of maximum lifespans should focus on the oldest age attained over time. As the graph we cite in our note shows, maximum lifespans have tended to steadily rise over time with no looming limit in sight.
And that, of course, it exactly the point I was trying to make. If new advances in the science of aging are taking place, people are going to be staying alive longer, rather than dying. Now, to be sure, as Eddie and I discussed, the potentially dramatic changes in old age science could really alter the picture of human lifespan--or they may just make us healthier until we die at an age no older than 122. Only time will tell.


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  2. Actually I think it's only Olshansky (rather than Vaupel) who asserts there's an upper limit to be seen at this point.

    Here is a link to that neat Wilmoth and Horiuchi (I forgot there were TWO authors) on "rectangularization," which I think is good evidence for Vaupel's side of the debate:
    Esp that (as of 1999) in recent decades rectangularization had slowed even though life expectancy continued to increase (that is (as I understand it), the rectangle is shifting to the right rather than just getting more rectangular).