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The Quest for Longevity Is Already Over
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science
Apr 2023
Jean-Marie Robine is not impressed by your centenarian grandma. Sure, she's sprightly for her age, but how unusual is making it to 100, really? Robine is a demographer and longevity researcher, and in his home country of France alone there are 30,000 centenarians; 30 times more than there were half a century ago. Add up all the centenarians worldwide and you get to 570,000--an entire Baltimore's worth of extremely long-lived humans. Having a birthday cake with 100 candles is nice, but nowadays it's nothing special.
To really pique Robine's interest we need to up the longevity stakes a little. He is an expert in supercentenarians: people who live to 110 or even longer. In the 1990s Robine helped validate the age of the oldest person who ever lived. Born in 1875, Jeanne Calment lived through 20 French presidents before dying in 1997 at the age of 122, five months, and 15 days. Since then Robine has become a collector of the super long-lived, helping run one of the largest and most-detailed databases of extremely old people.
For Robine, each supercentenarian is a crucial datapoint in the quest to answer a big question: Is there an upper limit to the human lifespan? "There are still many things we don't know. And we hate that," says Robine. But there is an even more fundamental question that undercuts the whole field of longevity research. What if--in our quest to push the limits of human lifespan--we're looking for answers in all the wrong places?
If you've ever read an interview with a supercentenarian, there is one question that will inevitably come up: What's the secret? Well, take your pick. The secret is kindness. Not having children. Connecting with nature. Avoiding men. Or, being married. Smoking 30 cigarettes a day. Not smoking 30 cigarettes a day. Drinking whisky. Abstaining from alcohol altogether. We mine the lives of the super-old for hints on how we should live our own.
But this is the wrong way to approach the question, says Robine. His style is to step back, take a look at how many supercentenarians there have been, and figure out when they lived and died. The limits of human longevity won't be found by looking at individuals, he believes, but by examining super-long-lived people collectively. It's a statistical puzzle: to crack it, you need to know exactly how many people died at age 111, 112, 113, and so on, to work out the likelihood that a supercentenarian won't make it to their next birthday.
In 1825, the British mathematician Benjamin Gompertz published one of the first attempts to calculate the limits of human longevity following this approach. Armed with birth and death records from Carlisle and Northampton, Gompertz calculated how someone's risk of dying changed as they got older. Gompertz found that after a person hit their late twenties, their risk of dying in the subsequent year kept going up, year after year. But at age 92 something curious happened. Their annual chance of death leveled off at 25 percent per year. This finding was odd. It suggested to Gompertz that there was no upper limit to human aging. Theoretically, he mused, there was nothing in his data suggesting that humans couldn't live for many, many, centuries--just like the lives of the patriarchs in the Bible.
But statistics is a cruel science, and Gompertz knew that too. According to his data, the risk of dying at age 92 was so high that you would need an unthinkably large number of humans to reach that age before you found just one person who lived to 192. Three trillion humans, to be precise--30 times more than have ever been born. And yet Gompertz found himself hampered by his dataset. So few humans made it past the age of 90 that it was hard for him to really know what mortality rates were like at very advanced ages. Did his results point toward some insurmountable limit to human lifespan, or just a temporary cap that could be lifted with advancements in medicine?
Modern demographers have picked up where Gompertz left off, sometimes with surprising results. In 2016 Jan Vijg and his colleagues at the Albert Einstein College of Medicine in New York concluded that mortality rates past the age of 100 start to rise rapidly, putting a cap on human lifespan of around 125 years. Two years later another group of demographers, this time led by Elisabetta Barbi at Sapienza University in Rome, came to the opposite conclusion. She argued that human death rates increase exponentially up until age 80, at which point they decelerate and then level-off after age 105. Barbi's research raised the tantalizing prospect that there is no upper limit to human lifespan at all, just like Gompertz wondered.
If mortality rates really do plateau at a certain age, then extreme longevity is just a numbers game, Robine says. Say you had 10 people reach the age of 110, and the risk of any of them dying each subsequent year had plateaued at 50 percent. You'd expect five of them to reach the age of 111, two or three to reach 112, one or two of them to reach 113, just one to reach 114, and no one to make it to 115. To have a good shot of someone reaching 115, you need to double the number of people making it to age 110, and so on. In other words, the upper limit on lifespan is just a factor of how many people survived the previous year. But these numbers all hinge on exactly what and where the mortality plateau is. The problem is, the data available for calculating this isn't very good.
The best global dataset on death is the Human Mortality Database, but it lumps everyone aged above 110 into one group. Then there's the International Database on Longevity (IDL), a dataset that includes people living and dead who reached the age of 105 and beyond, which Robine helped set up in 2010. At its peak the IDL had data from 15 countries, but tightening data privacy regulations mean that more recent data coverage is patchy. Some countries have since partially withdrawn what they included.
Japan, for instance, has more centenarians per capita than anywhere in the world, but in 2007 its Ministry of Health, Labor, and Welfare reduced the amount of publicly-available data on its centenarians--meaning one of the richest sources of super-long-lived people is no longer producing useful information. And in countries that produce good data, the process of validating and tracking down birth records that can date back to the early 19th century is still laborious and frustrating. To validate Jeanne Calment's age, Robine quizzed the supercentenarian about her early life, checking her answers against church records, censuses, and death certificates. Even so, the IDL contains records on just under 19,000 individuals, living and dead, from 13 countries. But for Robine, it's vital to collect even more.
Robine's friend Jay Olshansky, an epidemiologist at the University of Illinois at Chicago, has a different take on the matter. "Whether mortality rates plateau or whether they continue to rise is probably completely irrelevant," says Olshansky. The sheer fact that it's hard to generate reliable death rates past the age of 110 tells us everything we need to know about the upper limit on human longevity, he says--the fact there are so few supercentenarians tells us we've already reached the upper limit to human longevity. As the only person ever to live longer than 120, Jeanne Calment is simply a statistical outlier, Olshansky says. Other people might break her record by a few years, but it doesn't mean that human lifespans are heading up, and up, and up.
In fact, Olshansky thinks that our obsession with ultra-long-lived humans is the wrong approach. "Studying these extremely long-lived people is like studying Usain Bolt when it comes to running and saying, 'Yeah, we can all run that fast,'" he says. "To hold them up as what's possible for everyone is naive." On the contrary, Olshansky says that the quest for longevity in the developed world is mostly already over. We already live exceptionally long lives, he points out. In 1990 Olshansky wrote a paper arguing that eliminating all forms of cancer--which was responsible for 22 percent of US deaths at the time--would only add three years to the average US life expectancy. Once you get to a certain age, if one thing doesn't kill you, then there's something else around the corner that will.
Olshansky argues we should shift our attention to helping people live healthier lives, rather than simply focusing on overall lifespan. That's a view shared by Juulia Jylhava, a principal researcher at Karolinska Institutet in Sweden and a data scientist at MedEngine, a medical data science company based in Finland. "We should surely be more focused on healthspan and how to maintain not only health, but also functional abilities," says Jylhava.
Healthspan--years lived in good health--might be the unsexy cousin of longevity research, but figuring out ways for people to live healthier lives could have a much greater impact than extending lifespan by a few years. A big part of extending healthy lives is pinpointing when people start to decline in health, and what the early indicators of that decline might be. One way is by looking at frailty--a measure that usually takes into account factors like social isolation, mobility, and health conditions to produce an overall frailty score. In England, the National Health Service automatically calculates frailty scores for everyone aged 65 and over, with the aim to help people live independently for longer and avoid two major causes of hospital admissions for older people: falls and adverse responses to medication.
But Jylhava's research suggests that frailty indicators might be useful much earlier in life, too. She found that increased frailty scores were associated with higher mortality risks in old age, but that this association was particularly pronounced at age 50, where a jump in frailty score indicated a relatively large increase in mortality risk. Jylhava says this is a sign that assessing frailty at age 65 is too late. Rather than looking to the ultra-old for the key to healthy aging, we should actually be looking at when and why younger people start the decline into ill health.
Of course, the lives of supercentenarians provide us some hints about what it takes to live a very long life. We know, for instance, that there are genetic drivers of longevity in both animals and humans. Earlier this year, a French nun named Lucille Randon died at the age of 118 and 340 days. Robine is looking at her genealogy to find out whether she--like Jeanne Calment--also had ancestors who lived exceptionally long lives. Find families of long-lived people, and more life-extending genes might reveal themselves. But even people with exceptionally good genes who make it all the way to 110 or more are still extreme statistical outliers. As the baby boomers reach their centenary around the middle of the 21st century, and the number of people in old age swells, we can expect the number of very old people in the developed world to shoot up. But such a trend is far from a guarantee that anyone will surpass Jeanne Calment's 122 years.
Perhaps that's the real secret of the supercentenarians--how much of their lifespan is really beyond our control. Even if more of us are blessed with good genes, healthy lifestyles, and excellent medical care, it doesn't mean we should expect longevity records to come crashing down. Robine looks a lot younger than his 71 years, and he often gets asked what his secret is. "I know the secret because Jeanne Calment told me it," he usually responds. But the truth is that Calment--unlike other supercentenarians--never shared her longevity tips with Robine. She had no secret at all.
