Age limit: Have we hit a ceiling for longevity? Not so fast, some experts say

For as long as humans have been aware of their mortality, the question of whether a limit exists to the maximum age we can reach has followed. Attempts to reach this ceiling have attracted a wave of pseudoscience, from injecting the blood of younger people to tests that can tell one's "true age." It seems many people want to reach or exceed the age of Jeanne Calment, the oldest verified living person who died at 122 years, 164 days or Maria Branyas, recently the world’s oldest living person, who died in August in a Spanish nursing home aged 117.

Longevity researchers have been arguing about this question for decades, and a new study published this week reignites this fiery debate among researchers about whether humans will continue to live longer forever or some day reach a lifespan ceiling.

In the past century, average life expectancy has doubled from 32 years in 1900 to 71 years in 2021, according to Our World in Data. Advancements in medicine and technology allowed us to live longer and longer, and the global lifespan among high-income countries has continued to steadily increase until the present day by about three years per decade throughout much of the 20th Century.

However, a new study published this week in Nature Aging says that this upward trend is curbing and boldly states that “humanity’s battle for a long life has largely been accomplished.” Using data from eight wealthy countries with the highest life-expectancies plus the U.S. and Hong Kong, researchers reported that increases in life expectancy slowed between 1990 to 2019. (The authors did not include more recent years to avoid conflating the data with deaths caused by the COVID-19 pandemic, which reduced life expectancies.)

"Our analysis suggests that survival to age 100 years is unlikely to exceed 15% for females and 5% for males, altogether suggesting that, unless the processes of biological aging can be markedly slowed, radical human life extension is implausible in this century," the authors report.

The only places in the study to undergo a “radical life extension” like what occurred in the 20th Century, defined in the study as a 0.3-year annual improvement in life expectancy across this time span, were South Korea and Hong Kong.

Study co-author Dr. S. Jay Olshansky, a public health professor at the University of Illinois at Chicago, attributes the increased longevity observed throughout most of the 20th Century to major medical advances like antibiotics and vaccines that saved young people, in particular. Saving younger children earlier in life, Olshansky explained, equated to more years of life saved compared to advancements in technology and their coinciding years of life saved among older people today. 

“In epidemiology, this is called competing risk, which is just another way of saying we have a large number of diseases that compete for our lives,” Olshansky told Salon in a phone interview. “The older you get, the more of them there are. It's like a game of Whac-a-Mole.”

The globale $62 billion anti-aging market suggests plenty of people want to extend their lifespan, and changes in longevity impact the way we work, retire, and care for our aging populations. Increases in longevity have slowed in many high-income countries in the past couple of decades, but other researchers asked to comment on the study said life spans are expected to continue to grow, even if it’s at a slower rate. Since 1960, life expectancy in these countries has improved by about six years per decade, said John Bongaarts of the Population Council in New York City, who was not involved in the study.

One exception is the U.S., which has experienced decreases in life expectancy in recent years, an outlier among other wealthy nations. This could be in part due to co-occurring obesity, drug overdose, and maternal mortality crises that don’t happen in other countries at the same rate.

“If you leave out the U.S., then the rest of these countries are steadily seeing improvements in life expectancy, and that pace of improvement is likely to continue,” Bongaarts told Salon in a phone interview. 

Medical advancements are steadily improving at saving older people, and while longevity gains might not be as drastic as they were when advancements in technology were saving younger people, it still has a net positive effect, said Shripad Tuljapukar, a professor of biology and population studies at Stanford University in Palo Alto, California. People at older ages, for example, are dying later and later with “old-age survival [following] an advancing front, like a traveling wave,” according to a 2018 study Tuljapukar published in PNAS.

“People are getting older and dying of things they didn’t die from 30 years ago or 40 years ago,” Tuljapukar told Salon in a phone interview. Olshansky’s study revisits a prior 1990 study published in Science titled "In search of Methuselah: Estimating the upper limits to human longevity," which reported it was "highly unlikely that life expectancy at birth will exceed the age of 85."

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“I don't think there's really much that we can do to reaccelerate things forward like they did in the past,” Olshansky said. “You have to come up with something that is going to add three, four, or five decades of life to a 90-year-old — and that is not going to be so easy.”

However, the life expectancy for women in Japan, which is the world's longest-lived country and is often looked to as a preview of what to expect regarding changes in life expectancy in other high-income countries, has already exceeded 85.

Moreover, others think there could indeed be technological advancements that allow us to change the biological process of aging itself, and there is an entire field of research dedicated to reversing the effects of cellular aging. There’s some debate across disciplines about what causes aging, with some believing it’s a natural cellular “rusting” phenomenon that occurs independently of disease and gradually wears down the body until death, said Michael Rose, an ecology and evolutionary biology professor at the University of California, Irvine. 

Rose disagrees with this hypothesis and points to the existence of multicellular animals, which have the same basic cell biology as humans, that don’t age at all. 

“People in my field, we've now been saying for some time that … you can in fact radically transform the prospects for aging and dying,” Rose told Salon in a phone interview.

No one can know whether or when technological advancements could occur on a grand enough scale that they could meaningfully alter life expectancy trajectories in the years to come without a crystal ball, and this study stirs up the decades-old question of whether there is a limit to life expectancy itself.

“I don’t think we know the answer to the question,” Tuljapukar said. “But even if we don’t know that … We will definitely see a lot more people living to higher ages. There is no question about that.”

Whether or not there is a true limit to how old people can reach, perhaps we can expect more Jeanne Calments and Maria Branyas to exist.