Are We Reaching the Limit of Human Longevity? A New Study Says Yes

Human life expectancy dramatically increased last century. Compared to babies born in 1900, those born at the turn of the 21st century could live, on average, three decades longer—with many living to celebrate their 100th birthdays. In other words, for much of the century, each passing year added something like three months to a person’s potential time on Earth.

To optimists in the longevity field, the rapid rise in life expectancy will likely continue at a steady, if not accelerated, pace.

Others have a more pessimistic view. In their predictions, humans will hit a natural ceiling, with the average person in developed countries living to an age far less than 100.

A new study adds to the debate with analysis of data from 1990 to 2019. After examining life expectancy from eight countries with the longest living populations, plus those from Hong Kong and the US, the team reached a troubling conclusion: Despite innovations in healthcare, the increase in overall life expectancy is slowing down.

“Most people alive today at older ages are living on time that was manufactured by medicine,” said study author S. Jay Olshansky, a veteran researcher of aging at the University of Illinois. “But these medical Band-Aids are producing fewer years of life even though they’re occurring at an accelerated pace, implying that the period of rapid increases in life expectancy is now documented to be over.”

The team’s analysis suggests that only 15 percent of females and 5 percent of males will live to 100 years old. In other words, “unless the processes of biological aging can be markedly slowed, radical human life extension is implausible in this century,” they wrote.

The paper is sparking heated discussion between scientists and investors in the field.

“One of the most intriguing and lively scientific disputes concerns the future of human lifespan,” wrote Dmitri Jdanov and Domantas Jasilionis at the Max Planck Institute for Demographic Research and the Max Planck–University of Helsinki Center for Social Inequalities in Population Health, respectively, who were not involved in the study.

A Divided View

Human life extension sounds sci-fi. But thanks to modern medicine, it’s already happened. Medical innovations and public health measures have dramatically increased human life expectancy over the last century.

Rewinding back to the late 19th and early 20th centuries, antibiotics weren’t available as a first-line treatment for a scrape or a wound. Few vaccines were widely used against a variety of spreadable diseases—typhoid, cholera, and plague. Handwashing was just starting to be adopted by surgeons—although shockingly, the practice wasn’t mandated until the 1980s.

The recent explosion of biomedical technologies lends itself to an optimistic outlook on life extension. Engineered immune cells can now fight off previously untreatable cancers and are beginning to tackle deadly autoimmune diseases. Organ transplant and “smart” implants can rejuvenate broken down organs. Medical imaging technologies capture diseases at early stages and help expecting mothers track pregnancies, lowering the risk during delivery. If the pace of discovery continues, more treatments and technologies could be on the horizon.

The pessimists also have a case. In their view, human lifespan has a hard ceiling. Like houses, cars, or other complex structures, our bodies eventually break down. Cells deteriorate, aggregating clumps of toxic waste that cloud the brain. Heart cells and blood vessels struggle to keep blood pumping. Kidneys and livers lose their function. Efforts to reverse age-related diseases—dementia, heart disease, cancer, sensory, and metabolic problems—only temporarily reverse or slow aging.

“Our bodies don’t operate well when you push them beyond their warranty period,” Olshansky told Scientific American. “As people live longer, it’s like playing a game of Whac-a-Mole…Each mole represents a different disease, and the longer people live, the more moles come up and the faster they come up.”

An Age Ledger

Olshansky has been skeptical of radical life extension since 1990, when he predicted that human life expectancy gains would slow down regardless of medical interventions. But he’s interested in the fundamental question: How much longer are humans capable of living?

In 1990, his team had already “hypothesized that humanity is approaching an upper limit to life expectancy” at roughly 85 years. But some argued the initial study didn’t take into account the potential of future advances in medicine and biology.

Almost four decades later, the new results support his original finding. For the study, the team examined death rates and life expectancies from 1990 to 2019 for the eight countries with the longest-living individuals. They’re spread across the globe—South Korea, Japan, Australia, France, Italy, Switzerland, Sweden, and Spain, along with Hong Kong and the US, both of which have relatively reliable medical records. Much of the data came from the Human Mortality Database, which hosts health measures and life expectancy of people between 1950 and 2019.

From 1950, the average life expectancy increased continuously throughout all populations until 2019.  However, regardless of country, overall increases in life expectancy have slowed down in the past decade—with an especially large drop in the US.

South Korea and Hong Kong fared the best, with a less dramatic downturn in life expectancy. Even so, only roughly 14 percent of female children and roughly 4.5 percent of male kids born in 2019 are expected to reach 100 years of age. The US fared worse, with only a little over 3 percent of female children and one percent of males born around 2019 expected to live to 100.

Overall, this means that if a man and a woman live to 50 years of age, she’ll likely live to 90 on average, whereas he’d hit 85.

“Our result overturns the conventional wisdom that the natural longevity endowment for our species is somewhere on the horizon ahead of us—a life expectancy beyond where we are today,” Olshansky said.

Long Road Ahead

According to a previous analysis, no country has shown a continuous increase in life expectancy since the 19th century. But that doesn’t mean records can’t be broken. The study left the fundamentals of biological aging—why our tissues break down, why we struggle with age-related diseases—to further research.

“Additional insights into future longevity prospects” may arise from studying exceptionally long-lived groups, wrote Jdanov and Jasilionis. Dubbed “longevity vanguards,” these people hold record life expectancy. By analyzing their biology, diets, and other life-long practices, such as religion, scientists are beginning to discover why. Similar to analyzing public health trends, adding social factors, such as education, could make the predictions more accurate—not just for the vanguards, but for humanity as a whole. To be clear, these analyses can’t estimate a single person’s life expectancy. Rather, they gauge an overall picture of longevity trends.

Olshansky expects the new results to be controversial. But instead of focusing on life extension—the number of years people can live—he wants the field to zero in on extending healthspan—that is, the number of healthy years people enjoy.

The team acknowledges their projections didn’t factor in current methods for battling age-related treatments—for example, metformin, senolytics that target “zombie cells,” or genetically engineered cells that can wipe out toxic immune cells during aging.

Those approaches may be next steps. Compared to last century, we already know so much more about how and why our bodies age.

Olshansky agrees. “There’s plenty of room for improvement…We can push through this glass health and longevity ceiling with geroscience and efforts to slow the effects of aging.”

Image Credit: Gerd Altmann / Pixabay