November 13, 2024

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New Research Suggests Human Lifespan May Have Reached Its Limit

New Research Suggests Human Lifespan May Have Reached Its Limit



New Research Suggests Human Lifespan May Have Reached Its Limit

Throughout most of the 20th century, the average life expectancy in developed countries increased by approximately three years every decade. For individuals born at the turn of the 21st century, these incremental gains translated to an additional 30 years of life compared to those born in 1900, with an average lifespan reaching 80 years.

This phenomenon, known as “radical life extension,” has been a gift to humanity, made possible by advancements in medical technology and public health measures. Many scientists and laypeople alike believed that this trend would continue indefinitely, with human lifespans extending at the same rate. However, others predicted that humans would encounter a natural ceiling, with average life expectancy in the world’s longest-living countries peaking before reaching 100 years.

Recent research on this contentious issue suggests that humans may have already reached the upper limit of lifespan. Despite ongoing progress in medical technologies aimed at extending life, the study’s findings indicate that the rate of increase in average life expectancy has slowed down in the longest-living countries over the past three decades.

S. Jay Olshansky, a professor of public health at the University of Illinois Chicago and lead author of the new study published in Nature Aging, attributes this slowdown to aging – a series of poorly understood biological processes that result in frailty, dementia, heart disease, and sensory impairments. He states, “When you push the body beyond its warranty period, it doesn’t function well anymore.”

“As people live longer, it’s like playing whack-a-mole,” Olshansky adds. “Each mole represents a different disease, and the longer people live, the more moles appear and the faster they pop up.”

In 1990, Olshansky published a paper in Science predicting that the growth rate of human life expectancy would slow down even with accelerated medical progress. His conclusion at the time was that it was “highly unlikely” for human average lifespan to exceed 85 years.

The paper faced widespread opposition, as Olshansky notes, “There were vested interests in the notion that life expectancy would continue to rise.” Nevertheless, Olshansky remained convinced of his hypothesis. He decided to “be a patient scientist” and revisit his assumptions once real-world data became available. After 34 years, the wait has paid off with “a clear affirmation” supporting his initial findings.

Olshansky and his colleagues employed a straightforward approach: they examined changes in mortality rates and life expectancy from 1990 to 2019 in the world’s eight longest-living countries – Japan, South Korea, Australia, France, Italy, Switzerland, Sweden, and Spain – as well as the United States and Hong Kong. They discovered that the rate of life expectancy improvement had slowed in almost all of these places, with the United States actually experiencing a decline in life expectancy.

South Korea and Hong Kong were exceptions. Olshansky explains that the accelerated recent improvement in survival rates in these two places is likely related to their concentrated surge in life expectancy over the past 25 years. Even so, in Hong Kong – home to the world’s longest-living population – researchers found that only 12.8% of female children and 4.4% of male children born in 2019 are expected to reach 100 years of age.

These figures are significantly lower in the United States, where only 3.1% of female children and 1.3% of male children are projected to live to 100.

 

New Research Suggests Human Lifespan May Have Reached Its Limit

Amanda Montanez; Source: U.S. Census Bureau: “Implausibility of Radical Life Extension in Humans in the Twenty-First Century,” by S. Jay Olshansky et al., Nature Aging. Published online October 7, 2024 (data).

 

 

To put their findings into perspective, Olshansky and his colleagues also calculated what life expectancy would look like if humans were truly keeping pace with radical life extension. For instance, in such a scenario, 6% of Japanese women would live to 150 years, and about one-fifth of Japanese women would surpass 120 years. “We didn’t call these scenarios ‘absurd’ in the paper,” Olshansky says, “but we hope people will come to that conclusion on their own.”

Jan Vijg, a biologist and geneticist at Albert Einstein College of Medicine who was not involved in the study, says the new paper’s approach and conclusions “make a lot of sense.” He adds, “There really is no evidence that survival to 100 is going to become a reality anytime soon.”

Vijg notes that the new paper’s findings echo previous studies, including one he and colleagues published in 2016, which also concluded the existence of a lifespan limit. “After our paper came out, we were inundated with responses from the scientific and non-scientific community saying we were charlatans, our data was flawed, there was no evidence for a lifespan limit. Needless to say, our data was never found to be flawed,” Vijg says.

Despite the weight of the new evidence, Olshansky fully expects that he and his colleagues’ findings will be controversial.

However, he believes scientists should shift their focus away from the “unproven hypothesis” of continuing radical life extension and toward “geroscience” – a relatively new field of study that emphasizes extending people’s “healthspan,” or the number of healthy years people can enjoy, rather than overall lifespan. Olshansky and his colleagues write in the new paper that unless new technologies can address the aging process, further radical life extension in already long-lived countries “remains implausible.”

Nalini Raghavachari, a program officer at the U.S. National Institute on Aging who was not involved in the study, also believes that research should focus on understanding and achieving healthy aging. She suggests that clues to how this might be accomplished could come from some of the world’s longest-lived populations. “A deeper understanding of the protective influences and mechanisms behind exceptional healthspans could lead to the development of new therapeutic targets and interventions to promote healthy aging,” Raghavachari adds.

This research highlights the complex interplay between medical advancements, biological limitations, and the pursuit of longevity. As we continue to explore the frontiers of human lifespan, the focus appears to be shifting from merely extending life to enhancing the quality of our later years. The challenge now lies in translating these findings into practical interventions that can help people not just live longer, but live healthier and more fulfilling lives well into old age.

New Research Suggests Human Lifespan May Have Reached Its Limit

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