A new study suggests there may be a hard limit on human longevity, reports Live Science's Rebecca Sohn. That upper limit, according to the study published this week in the journal Nature Communications, is somewhere between 120 and 150 years old.
At that advanced age, the researchers say the human body simply would no longer be able to bounce back and repair itself after normal stresses such as illness, according to the Guardian. The study is based on medical data from more than 500,000 volunteers that the team behind the study collated into a single number that measures the physiological toll of aging that they called the “dynamic organism state indicator” or DOSI.
This figure distinguishes biological age, which is essentially how run down your cells and organ systems are, from chronological age in a manner that recalls a scene from the Indiana Jones film Raiders of the Lost Ark (1981) in which a banged up but still youthful Harrison Ford groans, “it’s not the years honey, it’s the mileage.”
“What we’re saying here is that the strategy of reducing frailty, so reducing the disease burden, has only an incremental ability to improve your lifespan,” Peter Fedichev, a longevity researcher at the Moscow Institute of Physics and Technology and senior author of the study, tells Sophie Putka of Inverse.
Per Live Science, the suggestion is that increasing the human lifespan beyond this hard limit would require therapies that boosted and maintained the body’s ability to be resilient and repair itself.
Researchers gleaned this upper limit on human life from anonymized blood samples from 544,398 people in the United States, United Kingdom and Russia. The team primarily looked at two numbers to determine the individual’s DOSI: the ratio of two types of white blood cells that the immune system uses to fight infection and the variability in the size of red blood cells, according to Live Science. Each of these numbers tend to increase as people get on in years and are referred to by researchers as biomarkers of aging.
The researchers calculated the human lifespan’s potential upper limits by plugging these biomarkers of aging, along with other basic medical data on each volunteer, into a computer model.
“They are asking the question of ‘What’s the longest life that could be lived by a human complex system if everything else went really well, and it’s in a stressor-free environment?’” Heather Whitson, director of the Duke University Center for the Study of Aging and Human Development and who was not involved in the study, tells Emily Willingham of Scientific American.
The team’s computer model suggested that even under completely ideal biological circumstances, these biomarkers of aging would have declined so much by 150 years of age that they could no longer support a living organism.
But it’s not clear that making it to 150 would necessarily be pleasant. As S. Jay Olshansky, an epidemiologist at the University of Illinois at Chicago who was not involved in the study, tells Scientific American, a long lifespan is not the same thing as a long health span.
“Death is not the only thing that matters,” Whitson tells Scientific American. “Other things, like quality of life, start mattering more and more as people experience the loss of them.”
The kind of death this study postulates, she tells Scientific American, “is the ultimate lingering death. And the question is: Can we extend life without also extending the proportion of time that people go through a frail state?”