Limits of the Human Life Span: How Long Is Long Enough?

 

Sonnet 73

That time of year thou mayst in me behold
When yellow leaves, or none, or few, do hang
Upon those boughs which shake against the cold,
Bare ruined choirs, where late the sweet birds sang.
In me thou see’st the twilight of such day
As after sunset fadeth in the west;
Which by and by black night doth take away,
Death’s second self, that seals up all in rest.
In me thou see’st the glowing of such fire,
That on the ashes of his youth doth lie,
As the death-bed, whereon it must expire,
Consumed with that which it was nourish’d by.
This thou perceiv’st, which makes thy love more strong,
To love that well, which thou must leave ere long.

By William Shakespeare

In “Sonnet 73,” Shakespeare speaks of approaching old age and mortality. The speaker in the poem slowly comes to grips with the real finality of his age and his impermanence in time. The couplet of this sonnet renews the speaker's plea for the young man's love, urging him to “love well” that which he must soon leave.

“But just how long could a human actually live? It’s a question people have been asking for centuries. While average life expectancy (the number of years a person can expect to live) is relatively easy to calculate, maximum life span estimates (the greatest age a human could possibly reach) are much harder to make. Previous studies have placed this limit close to 140 years of age. But a more recent study proposes that the limit to human life span is closer to 150.”

– Richard Faragher, Professor of Biogerontology at the University of Brighton and past Chair of both the British Society for Research on Ageing and the International Association of Biomedical Gerontology

To conduct the modeling study, the researchers took blood samples from over 70,000 participants aged up to 85 and looked at short-term changes in their blood cell counts. The number of white blood cells a person has can indicate the level of inflammation (disease) in their body, while the volume of red blood cells can indicate a person’s risk of heart disease or stroke, or cognitive impairment, such as memory loss. The researchers then simplified this data into a single parameter, which they called the dynamic organisms state indicator (Dosi).

Changes in Dosi values across the participants predicted who would get age-related diseases, how this varied from person to person, and modeled the loss of resilience with age. These calculations predicted that for everyone – regardless of their health or genetics – resilience failed completely at 150, giving a theoretical limit to human life span.

But estimates of this type assume that nothing new will be done to a population, such as, no new medical treatments will be found for common diseases. This is a major flaw, since significant progress occurs over a lifetime and this benefits some people more than others.

(Kyoung Min Kim, Li-Yung Lui, Warren S Browner et al. “Association Between Variation in Red Cell Size and Multiple Aging-Related Outcomes.” J Gerontol A Biol Sci Med Sci. June 14, 2021.)

Faragher reports …

“Intuitively, there should be a relationship between your chance of death and how rapidly and completely you recover from illness. This parameter is a measure of your ability to maintain homeostasis – your normal physiological equilibrium – and is known as resilience. In fact, aging can be defined as the loss of ability to maintain homeostasis. Typically, the younger the person, the better they are at recovering rapidly from illness.”

(Richard Faragher. “Is 150 years really the limit of human life span?” The Conversation. June 8, 2021.)

Faragher says if you’re planning to beat the Dosi limit, you need three important things.

1. Good Genes (These make living to more than 100 a good bet.)

2. Excellent Diet and Exercise Plans (Both can add up to 15 years to life expectancy.)

3. Breakthroughs In Treatments and Medicines

Currently, adding more than 15-20% to healthy life span in normal mammals is extremely difficult, partly because our understanding of the biology of ageing remains incomplete. But it’s possible to increase the life span of much simpler organisms – such as roundworms – by up to ten times. 

How Long Do We Want To Live?

Over three years David Ewing Duncan – award-winning journalist in print, television, and radio and best-selling author of ten books published in 21 languages – posed this query to nearly 30,000 people at the start of talks and lectures on future trends in bioscience. To make it easier to tabulate responses, he provided four possible answers: 80 years, currently the average life span in the West; 120 years, close to the maximum anyone has lived; 150 years, which would require a biotech breakthrough; and forever, which rejects the idea that life span has to have any limit at all.

Duncan made it clear that participants should not assume that science will come up with dramatic new anti-aging technologies, though people were free to imagine that breakthroughs might occur – or not.

The results: some 60 percent opted for a life span of 80 years. Another 30 percent chose 120 years, and almost 10 percent chose 150 years. Less than 1 percent embraced the idea that people might avoid death altogether.

These percentages held up as he spoke to people from many walks of life in libraries and bookstores; teenagers in high schools; physicians in medical centers; and investors and entrepreneurs at business conferences. He says he popped the question at meetings of futurists and techno-optimists and gotten perhaps a doubling of people who want to live to 150 – less than I would have thought for these groups.

(David Ewing Duncan. “How Long Do You Want to Live?” The New York Times. August 25, 2012.)

Curiously, after learning about future interventions that might thwart the impact of aging – such as bionics, stem cells that repair organs, and anti-aging pills – few people wanted to change their votes. Even if Duncan asked them to imagine that a pill had been invented to slow aging down by one-half, allowing a person who is, say, 60 years old to have the body of a 30-year-old, only about 10 percent of audiences switched to favoring a life span of 150 years.

Overwhelmingly the reason given was that people didn’t want to be old and infirm any longer than they had to be, even if a pill allowed them to delay this inevitability.

Others were concerned about a range of issues both personal and societal that might result from extending the life spans of millions of people in a short time. These included everything from boredom and the cost of paying for a longer life to the impact of so many extra people on planetary resources and on the environment. Some worried that millions of healthy centenarians still working and calling the shots in society would leave our grandchildren and great-grandchildren without the jobs and opportunities that have traditionally come about with the passing of generations.

Skepticism about aging has been found by other researchers. Duncan's poll supported studies by the Pew Research Center's Religion & Public Life Project (2013) that asked more than 2,000 U.S. adults about their desire to live longer, as well as their hopes for enhanced life expectancy and medical services.

Pew found only 38% of respondents said they would be willing to undergo treatments to extend their lives to 120 or beyond; 56 percent said they would not, although two-thirds said they believed most other people would. Most Americans, though, do expect to live longer than the current average U.S. life expectancy of 79, according to Pew. Asked how long they thought they would live, 69% stated an age between 79 and 100, with 90 being the median.

In general, respondents to the Pew survey were hopeful about medical advances to address cancer and other potentially fatal conditions. But they were deeply skeptical about life extension research. Three out of four adults said they doubted that people would routinely live to 120 by 2050. Slightly more than half (51%) said that development would be "bad for society;" 41% said it would be a good thing. Two-thirds of respondents said they imagined such advances would mostly benefit the wealthy and only a quarter expect that treatments would be properly tested before being released to the public.

(“Living to 120 and Beyond: Americans’ Views on Aging, Medical Advances and Radical Life Extension.” Pew Research. August 06, 2013.)

A new study (2021) sheds light on how the specter of dementia and chronic pain reduce people’s desire to live into older ages. Among Norwegians 60 years of age and older, the desire to live into advanced ages was significantly reduced by hypothetical adverse life scenarios with the strongest effect caused by dementia and chronic pain, according to research conducted at the Robert N. Butler Columbia Aging Center based at Columbia University Mailman School of Public Health.

(Vegard Skirbekk, Ellen Melbye Langballe, and Bjørn Heine Strand. “Preferred life expectancy and the association with hypothetical adverse life scenarios among Norwegians aged 60+” Age and Ageing. July 03, 2021.)

Answers

To most, quality of life matters more than longevity. Apparently, there is more to life than just making sure it doesn’t end. People are interested in living longer, but only if they continue to feel good enough to enjoy life, have decent mental abilities and mobility, and not be a burden on others. Future time is welcome so long as it occurs in the “third age” of independent living and not in the “fourth age” of vulnerability and decline. The Journal of Gerontology seemed to get it right when it published its first issue in 1946 under the banner: “To add life to years, not just years to life.”