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Have human lifespans maxed out at 115 years?

October 12, 2016

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One school of thought about human longevity believes that death should be treatable and curable—like a disease; while another can best be summed up by the old adage that in this world, “nothing is certain except death and taxes“.

Now a group of American scientists are saying that they’re not certain if any of us will be around to pay taxes much past the age of 115.

In a paper published October 5 in Nature, entitled “Evidence for a Limit to Human Lifespan”, three geneticists use global demographic data to argue that the steady increase in longevity, caused by improvements in health, diet and environment, that began in the 19th century, has leveled off at a maximum lifespan of 115 years—give or take.

Says the study’s senior author Jan Vijg, Ph.D.:

“Demographers as well as biologists have contended there is no reason to think that the ongoing increase in maximum lifespan will end soon but our data strongly suggest that it has already been attained and that this happened in the 1990s”.

The study’s three authors, who all hail from the Albert Einstein College of Medicine in the Bronx, New York, USA, assert that their data also “strongly suggest that the maximum lifespan of humans is fixed and subject to natural constraints”.

The data, it turns out, is meant to support a certain conclusion, namely that human beings have reached peak lifespan and therefore healthcare resources are better focused on quality over quantity, where lifespan is concerned.

However, the statistical data doesn’t actually warrant the conclusion that the study draws. All the data shows is that, with notable exceptions, the longest-lived human beings aren’t living much past 150—it doesn’t prove that they can’t, or won’t.

A skeptical person might ask what came first, the conclusion or the evidence.

Research anyone can do on the Internet in five minutes

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Dr. Vijg and his two colleagues arrived at their conclusion that human lifespans have finally peaked at around 115 years, not by using any sophisticated genetic analysis but solely by crunching numbers from the Human Mortality Database (HMD), an online resource which compiles mortality and population data from at least 37 countries.

Interestingly, the trio could’ve saved themselves a  lot of trouble and largely gotten the same results from Wikipedia’s “List of the verified oldest people“.

This list clearly indicates a sort of “glass ceiling” for lifespan around 115 years-of-age. And it shows what the study authors say was the high-water mark of life expectancy over 19 years ago, on August 4, 1997, when Jeanne Calment, a French super-centenarian, passed away at the singularly amazing and fully documented age of 122 years and 164 days.

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This list of the 100 verified oldest people also shows that the next-most long-lived person, American Sarah Knauss, passed away in 1999 at the age of 119 years and 97 days and that, overall, the decade of the 1990s saw the highest average death age—115.08—of any decade on record.

But what of it? The list also shows that that no less than six of the oldest verified super-octogenarians are still alive—three at age 114, one at 115 and three at 116—and who knows how long they will live?

And then there are all the cases of the unverifiables who are not included, such as Mbah Gotho, an Indonesian man who claims to have been born in 1870—which would make him an incredible 145 years old.

Independent, third-party verification of a claimed age is required for official recognition and it’s a lot to expect that a developing country such as Indonesia will have the necessarily detailed birth records, going back 145 years.

It’s no surprise that only one of the verified birth dates in the 1800s occurred in a developing nation (María Capovilla, Equador, 1889), or that 97 of the verified 100 oldest people are from Western and/or developed countries.

Developed/Western countries are the ones which, going back some 200 years, have had both the highest standards of living and record keeping and everything about this verified oldest person data is therefore skewed in the favour of these countries and to the exclusion of the rest of the world.

But put aside this biasit will be eliminated in the fullness of time (just not in our time).

Even if life expectancy has plateaued, there is nothing in the demographic data itself to tell us why and certainly nothing to indicate that genetic hard-wiring is responsible.

Who’s to say that as-yet-unidentified environmental factors aren’t stalling further gains in life expectancy—factors such as the global use of petroleum, or plastics or the widespread use of aluminum cookware for food preparation.

Do not historians link the fall of the Roman Empire to lead poisoning, from eating food cooked in lead pots and drinking water out of lead pipes?

Does genetic hard-wiring explain why Canadians, on average, have about a decade-more of life expectancy than our next door neighbours, the Americans?

The correct answer is that we do not have enough information to know.

On a hot summer’s day ice cream is to kill for, thus…

Jessica Hall, writing for Extreme Tech, explains that Dr. Vijg and his colleagues have confused correlation with causation—a logical fallacy called cum hoc ergo propter hoc.

The classic example Hall cites is between ice cream and murder.

The fact that ice cream sales and homicides correlate by peaking at the same time of year does not, by itself, prove a causal linkage between the two. There is no connection between the two, in fact—increased ice cream sales do not lead to more murders, or vice versa. The unseen causal factor is hot weather.

In the case of plateauing human life expectancy, Hall suggests that the unseen causal factor may be slight errors in DNA replication which—though not necessarily hard-coded—are still beyond our ability to prevent or repair at this time.

Nonetheless, Hall, who had full access to the study published in Nature (unlike this blogger), says that its authors make a worthwhile point; arguing that rather than extending lifespan, science should focus on extending the human health span to give people more quality of life.

This would seem like a self-evident truth but there is a catch.

This study comes at a time when all national healthcare systems—pressured by the incredible cost of specialty pharmaceuticals—are hotly debating the value of end-of-life cancer care on a hard cost/benefit basis and when some systems, like the UK’s NHS, are openly denying patients life-extending cancer drugs, solely on the basis of cost.

Even if the study were based on hard, incontrovertible science, I would still worry about bean counters wrongly using it to justify cutting back further on supplying life extending medical care.

The unseen causal relationship between money and medicine

To digress for a moment. Beginning in the 1980s, considerable lobbying began within the medical community for the increased use of opioid pain killers to treat chronic pain, as experienced by cancer patients. Studies were done and many scientific papers and scholarly articles were written, including the highly influential “The Tragedy of Needless Pain“, which appeared in Scientific American in 1990.

,Some of these papers and articles were based on rather flimsy data and made dubious claims. In the “Tragedy” article, for example, author Ronald Melzack stated that morphine, taken solely to control pain, was not addictive.

It turned out that more than a little of the inspiration and funding for this successful push to increase the proscribing of opioids for long-term pain relief came from pharmaceutical companies, like Purdue Pharma. Purdue made (and makes) the opioid painkiller OxyContin, which went on to became the company’s biggest moneymaker and, not incidentally, one of the most over-prescribed and abused prescription drugs of the early 21st century. It also helped pave the way for the fentanyl overdose crisis that we are now in the midst of.

Perhaps I’m overly suspicious but last week’s study of life expectancy offers less evidence for a limit to human lifespan than of a foregone conclusion scantily-dressed up with  insufficient and non-clinical evidence.

Past precedent makes me wonder if the whole thing wasn’t actually cooked up specifically to give bean counters an excuse to justify further cost-cutting of expensive, life-extending medications. Click the images to enlarge them.

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