Nearly 500 years before Jesus Christ walked the earth (and/or water), the Ancient Greek pre-Socratic philosopher, Democritus of Abdera, was considered the first noted example of the limits of human longevity. Which is to say, based on at least one historical account, Democritus was the first recorded centenarian.
Back then, of course — and through much of human history — sashaying your way through life toward 100 years was something of an anomaly. But today, thanks in large part to modern medicine and the Boomers that inundated the earth with a ton of humanity (in the physical sense, at least), the number of centenarians is up nearly 44 percent since 2000, per Smithsonian magazine. And according to a PBS report, between 1980 and 2010, the number of centenarians rose from 32,194 to 53,364, “an increase of almost 66 percent.” “The latest population estimate, released in July 2015, reflects 76,974 centenarians,” per the report.
The future of centenarians is bright, too — at least, for now. Luigi Ferrucci, a geriatrician and epidemiologist and the chief of the Longitudinal Studies Section at the National Institute on Aging, tells me it’s been estimated that 50 percent of the people born in 2000 will reach the age of 100: “Of course, estimating something that is a century in the future requires a lot of assumption and there are many variables that we cannot control for — pollution, new epidemic conditions, natural disasters, etc.” He’s right, especially when you consider that, due to the nearly irreversible climate change crisis, those born in 2000 will be lucky if they hit 50. Still, globally speaking, there’s never been a more fertile time for people to look into the future and announce that they’ll finally be able to retire once they hit 100.
Jokes aside, according to Thomas T. Perls, director of the New England Centenarian Study, recent human longevity trends have irrevocably changed the conversation around aging. “It wasn’t too long ago that people didn’t consider [aging to 100] lucky,” he says. “They considered it a bad thing to live to 100. They had this notion of the older you get, the sicker you get in the head. And they figured that if you got to be 100, you must have every age-related disease under the sun and be on death’s doorstep. And certainly, have Alzheimer’s disease.”
But try telling that to 107-year-old John Henderson, who, according to the same PBS report, is still active and free from any age-associated illnesses. As a semi-supercentenarian (that is, anyone over the age 105), he is often asked about his secret to a healthy 100. “Living in moderation,” Henderson told PBS. “We [his wife is also over 100 years old] never overdo anything. Eat well. Sleep well. Don’t overdrink. Don’t overeat. And exercise regularly.” (Full disclosure: I was scheduled to speak with Henderson for this article, but he had to cancel as he wasn’t feeling so well this week, and what was I going to do, repeatedly hassle a guy born in 1913 for an interview when he was under the weather? No thanks.)
Henderson is still the exception, of course, and the reality for most centenarians is a much more rapid collision with the limits of the human lifespan. “Even a ‘healthy’ 100-year-old tends to have many of the phenotypes of aging,” says Ferrucci. “Most, if not all, have hearing problems; they can walk, but stability and balance is usually a problem.” But the most important part — the brain — still functions more often than you’d think. “Cognition can be intact, and it is for a considerable percentage of centenarians,” says Ferrucci.
Both Ferrucci and Perls believe, then, that the most reliable sign of a “healthy” centenarian is the state of a person’s cognitive abilities once they hit 100. “It wasn’t too long ago that we realized that half of people over the age of 85 have Alzheimer’s disease, and that the incidence of the disease increases exponentially after that,” says Perls, adding that centenarians were believed to be at the highest risk. But Perls’ opinion changed when he became a physician at the Hebrew Rehabilitation Center in Boston. There, he had two patients over the age of 100 assigned to him who showed no signs of diminishing cognitive ability. “When I saw that they were completely cognitively sound, that was a huge surprise to me,” he says. “And certainly, completely went against the notion that by the time you get to 100, you inevitably would have AD [Alzheimer’s Disease].”
So what, then, separated the healthy centenarians who were still thriving at 100 years old, from those who reached the century mark with the help of a bevy of fun-colored pills and oxygen tanks? To better understand this spectrum of centenarian health, Perls and his colleagues began by differentiating 100-year-old individuals into three different categories. The first category, referred to as “survivors” — people who had a history of age-related diseases like strokes, cancer and heart attacks before the age of 65 — made up nearly 40 percent of their nearly 5,000 centenarian sample size. The second group, which made up another 40 percent of the sample, and who had age-related diseases after the age of 80, were referred to as “delayers.” And finally, the third group, which had none of the age-related diseases associated with increased mortality at the age of 100, were called “escapers.”
According to Perls, 90 percent of the centenarians were independently living, including the survivors and delayers. “What that told us was they had some kind of functional reserve or resilience that allowed them to deal with these diseases much better than other people,” he says. “And so, they could still be living independently into their 90s. That really seemed to be what was important. It wasn’t so much compression of disease, but rather the compression of disability characteristic of these individuals that was so important.”
In 1997 however — following the death of Jeanne Calment, the woman who established the world record for human lifespan at 122 years old — Perls and his team of gerontologists had to recalibrate their previous understanding of the limits of human life. “That’s how you define lifespan for any organism, the oldest member of the species,” says Perls. “So when she was 120, 121, every day that she lived she was extending human lifespan by a day. When she finally died at about 122, that’s about 20 years longer than the average age we were looking at.”
As a result, Perls and his team had to refine their sample size to include semi-supercentenarians (105 and older) and supercentenarians (110 and older). Once they did, they discovered that while centenarians made up a fairly mixed group of delayers, survivors and escapers, supercentenarians were mostly escapers. “When you start looking at the folks at the most extreme, when you start looking at these people like 108 and older for example, they become really alike.”
Specifically, Perls tells me that they found that supercentenarians shared a special combination of genetic variance that slows down aging and decreases the risk of age-related diseases — essential factors for living past the age of 105. “There was something protective going on,” he says. “It wasn’t just a matter of lacking genetic variance that might increase your risk for age-related diseases.”
What that “protective mechanism” is, Perl says, isn’t yet known. But what he did find was that, from a medical point-of-view, supercentenarians were “really quite homogeneous.” “If they’re medically quite alike, then you have to suspect that they’re quite alike in terms of these biological mechanisms,” he says.
Specifically, one facet that most centenarians and supercentenarians share is that they’re overwhelmingly women. “Eighty-five percent,” says Perls. “Women definitely have more of what it takes to get to these ages compared to men.” According to a BBC report, one potential reason why is that women tend to have two X chromosomes, which essentially gives them a backup. “That difference may subtly alter the way that cells age,” per the BBC report. “Having two X chromosomes, women keep double copies of every gene, meaning they have a spare if one is faulty. Men don’t have that backup. The result is that more cells may begin to malfunction with time, putting men at greater risk of disease.” Other hypotheses include the fact that, due to her menstrual cycle, a woman’s heart rate increases, offering the benefit of light exercise.
Perls notes, however, that while we still don’t fully understand the mechanisms that lead to longevity, the vast majority of humans have the genetic makeup — “the blueprint, if you will” — to be able to get them to 90. “If you looked at the Seventh Day Adventist population [25 million people worldwide], their average life expectancy is about 10 years longer than the rest of us,” he says. “They’re about 86 for men and 89 for women. And they’re a very mixed group when it comes to ethnicity and geographic location. But what they have in common are really good health behaviors.”
What, then, would cause a centenarian’s health to ultimately falter, if it’s not due to disease or hard living? According to Perls, it’s a combination of immunosenescence and muscle loss. “Immunosenescence is where the immune system starts to break down and you become more and more susceptible to infections,” says Perls. “Pneumonia and urinary tract infections and simple stuff that you just can’t combat. But there’s pretty significant frailty too. And that can be muscle loss, which is what we call sarcopenia. Those are kind of the major geriatric syndromes that we see in people at the very end of their lives.”
Which is to say, even those who hit the genetic lottery aren’t impervious to the forces of mortality.