The Future of Human Longevity

While the concept of living forever is still limited to science fiction movies, our lifespan has been increasing in the past decades. Researchers say that the upper limit of human longevity is yet to be reached, but it is necessary to ensure that these extra years are spent in good health.

The United Nations (UN) estimates that globally, life expectancy reached 72.8 years in 2019, nearly doubling in the past century. Jeanne Louise Calment from France died at the age of 122, earning the honor of being the world's oldest person. However, some researchers say that it is not necessarily the limit to the human lifespan.

In fact, the limit could be somewhere between 120 and 150 years old, according to a 2021 study published in the journal Nature Communications. The researchers examined blood samples from over 540,000 people to measure the "dynamic organism state indicator" (DOSI), a physiological toll of aging. They used two biomarkers of aging to determine the individual's DOSI. They found that under ideal biological circumstances, by 150 years, these biomarkers would have declined to a level no longer supporting a living organism.

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Another study published in PLOS One in 2023 analyzed data of people from 19 currently industrialized countries and found that people born between 1900 and 1950 are "experiencing historically unprecedented mortality postponement" but are still too young to break longevity records. The researchers predicted that these records may increase significantly in the coming decades.

"Our results confirm prior work suggesting that if there is a maximum limit to the human lifespan, we are not yet approaching it," the authors concluded.

May Reed, M.D., an associate professor at the University of Washington School of Medicine, says that although we likely haven't reached the limit of human lifespan, we should focus on compression of morbidity, which aims to minimize time at the end of life spent in a debilitated state.

"If we don't address that, we will have a collapse of the demographic imperative because we won't have enough people to take care of a huge number of debilitated older adults," she told Healthnews.

Indeed, healthspan doesn't keep pace with increasing lifespan, as the burden of chronic diseases is growing globally. For example, the cases of diabetes are estimated to more than double by 2050. The World Health Organization (WHO) has recently warned that chronic illnesses are taking an "immense and increasing toll on lives" as well as health systems, economies, and societies.

What determines the human lifespan?

John Tinniswood, who turned 111 years old in August, became the current oldest person in the United Kingdom. When asked about his secret to a long life, he talked about "moderation in all things," including nutrition and physical activity, and advised to "exercise the mind."

But simply following a rule of moderation may not work for everyone. Reed explains that genetics, such as diseases running in the family, limits the range of a person's lifespan. However, environmental factors, lifestyle, diet, exercise, and stress also play an important role in determining longevity. While all of these sound familiar, Reed says that a new variable to human lifespan has to be introduced — climate.

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The climate is now possibly taking an unprecedented role in determining how we age and how long we live.

- Reed

Climate change is the greatest risk to the longevity of future generations, according to the American Society of Aging. As it is expected to continue affecting the use and food production further and exacerbate pollution and distribution of diseases, these changes may negatively impact public health advances that contributed to increased lifespan in the 20th century. Climate change means a hotter world which has been linked to heart attacks and depression while wildfire smoke has been linked to asthma, lung conditions, and other physical complications.

Reed says that the means to increase healthspan depends on a country. In lower-resourced countries, the focus should continue on infectious disease prevention, vaccination, early childhood nutrition, and stress reduction. In the United States, it is essential to tackle problems like obesity, affecting one in four Americans. According to Reed, this could be done with a combination of dietary interventions, exercise, medications, and surgery.

Richard Miller, professor of pathology at the University of Michigan and a director at Paul Glenn Center for Biology of Aging, leads a research team that tests drugs that might prolong mice life. Out of 90 of the drugs tested thus far, eight had a significant benefit of extending the lifespan of the mice.

"More importantly, this gives us ideas about how aging works, how we can slow down aging in multiple systems if we understand more about the physiological factors that regulate aging as a unified process," he told Healthnews.

Miller says that it is now clear that drugs can extend mice's lifespan by up to about 25% or 30%, and it is possible to find drugs that could have the same effects in people.

Studies suggest that some medications already approved by the U.S. Food and Drug Administration (FDA) may increase longevity. For example, rapamycin, an immunosuppressant drug for transplant patients, extended life and delayed the onset of aging-related diseases in animal studies. Whereas canagliflozin, a type 2 diabetes drug, was shown to increase the lifespan of male mice.

Looking for new solutions to extend life

Although nowadays, we live much longer than people 200 years ago could imagine, the quest for even longer — or eternal — life continues. Some turn to cryopreservation, the process of vitrifying yourself in hopes of being revived in a healthy body, even though it can take decades to learn how to do so.

At the same time, the global market of anti-aging supplements is booming and is projected to grow from $63.01 billion in 2022 to $106.65 billion by 2030. Miller says that currently, the evidence that a pill could slow aging and extend lifespan is "close to zero," although there are some exceptions.

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"If you have high blood pressure, taking a pill for blood pressure regulation is a great idea. Or if you have high cholesterol, taking a statin is a great idea. You can certainly interfere with lethal diseases in people with medications," he said.

According to Miller, even if cancer or heart attack is eliminated in people over the age of 50, the average lifespan would increase only by 3% because many other conditions become lethal in older age.

And because aging is the biggest risk factor for developing these conditions, slowing it could increase life expectancy by 30 to 35 years, according to Ramkumar Hariharan, a senior scientist at the Institute for Experiential AI at Northeastern University.

Artificial intelligence may also play a role in extending lifespan, writes Professor Renato M.E. Sabbatini, a Brazilian biomedical and computer scientist. AI drives a personalized and precision medicine approach that considers each patient's unique genetic makeup and health history.

"This can lead to more effective treatments and preventions for diseases, ultimately increasing human longevity," he writes at Medium.

Scientists agree that the upper limit of human longevity hasn't been reached. However, predictions of the exact numbers are hard to make when new variables, such as climate change, are being introduced. And as artificial intelligence transforms medicine, its effects on human longevity are yet to be seen.

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