Despite the claims of anti-aging advocates and companies promoting ways to extend life, human life expectancy is actually slowing down after a period of growth in the previous century.
In a study published in Nature Aging, researchers led by S. Jay Olshansky, a public health professor at the University of Illinois in Chicago, report that the factors responsible for the significant increase in life expectancy during the 20th century are reaching a point of diminishing returns. Public health interventions such as clean water, improved sanitation and hygiene, along with medical advancements like vaccines and drug and surgical therapies, are approaching their maximum impact. To further extend human life expectancy beyond its current level, says Olshansky, entirely new strategies focused on manipulating the biological processes of aging are needed. And such strategies are not yet available.
A brief history of human life extension
At the beginning of the 20th century, humans began living longer primarily due to factors that reduced deaths among children and middle-aged adults—what Olshansky calls phase 1 of human life extension. These included basic sanitation practices and a better understanding of diseases and methods for preventing the spread of infectious agents like bacteria and viruses. Governments also assumed greater responsibility for public health protection. For instance, following the 1918 influenza pandemic, the federal government adopted a more active role in slowing down contagious diseases by promoting hygiene practices, isolation, and containment.
Phase 2 continued in the middle of the century with medical advances against specific diseases like heart problems and cancer. Vaccines against childhood diseases like measles and pertussis helped more children survive into adulthood. And advancements in treating most illnesses have further contributed to longer lifespans. In 1900, babies in the U.S. lived to about age 32—but by 2021, the average person lived to 71.
“We need to be grateful for what public health and medicine gave us and is still giving us, which is added survival time in the middle and now older ages,” says Olshansky. “The vast majority of people living beyond 60 are living on manufactured time—time created in phases 1 and 2 that enable us to live longer lives and enjoy life extension that our ancestors rarely had the opportunity to experience.”
Anti-aging headwinds
However, these interventions can only add so many years. This is because they are occurring alongside opposing forces that are driving down life expectancy and increasing mortality, including the rise of chronic diseases such as obesity and lifestyle practices such as smoking. Additionally, there is the immutable fact of biological aging itself. Despite all the gains in improving health, the body—our brains, bones, and muscles—and all of our systems continue to age; with chronic disease, they might even age more quickly. Back in 1990, “we predicted that this phenomenon of the limited lifespan hypothesis would play itself out at the beginning of the 21st century, and that the rise of life expectancy would start to slow down as the ability to manufacture time begins to wane,” Olshansky says.
And that is where we find ourselves in 2024. Researchers continue to study the benefits of a healthy diet and exercise in not just extending life, but adding healthy years, as well as new ways to preserve or even reverse aging processes. But, says Olshansky, “We need to accept the new reality that there is a limit to how long we can live. We are getting medical Band-Aids in phase 2 that are yielding smaller and smaller gains in longevity.”
The new research
Olshansky and his team analyzed data spanning 1990 to 2019 from the eight countries with the highest life expectancy, as well as Hong Kong and the U.S. (The U.S. is not among the longest-lived populations.) They documented a slowing in the increase in life expectancy during that period—and the U.S. was among several countries whose life expectancy was actually lower at the end of any given decade than it was at the beginning of that decade. Olshansky attributes that decline to higher deaths among middle-aged groups, perhaps due to substance abuse, suicide, and, more recently, COVID-19. Disparities in access to health care also mean that “some are doing so poorly that they are pulling down the average [life expectancy] for the population,” he says.
To achieve the dramatic longevity that anti-aging proponents currently promise without evidence—like living to 100 and beyond by fasting or taking certain supplements—life expectancy would need to increase by about three years per decade. But even in most of the longest-lived populations, the rate of improvement has slowed to under 2.5 years annually, making the claims unrealistic and unattainable under current disease models. And for life expectancy for newborns to reach 110 years, about 70% of females would need to survive long enough to become centenarians; currently, only about 5% of women in the longest-lived countries are expected to reach that milestone.
This does not mean that humans will not at some point routinely live into their 100s, says Olshansky. But given current trends, and without substantially improved methods for manipulating the biological processes of aging, that will not happen in this century. Despite the hype, no methods have proven to address and reverse aging. And those will be key to not only extending survival but ensuring that the added years are healthy ones and not plagued by frailty and disease.
“We got what we wanted—we got much longer lives,” Olshansky says. “But we are starting to see a rise in dementia, sensory impairment, and things that we are not able to manipulate quite as effective as we would like.”
The next step is to “deal with the consequences of our success,” he says. “Phase 3 should be focused on extending health span by going after aging itself and not just the diseases associated with it.”
