▎ WuXi AppTec content team editor
Just last week, China's oldest-lived elder died in Kashgar, Xinjiang, xinhua. Longevity has been the goal of human beings since ancient times. With the improvement of medical care and living standards, the average human life expectancy has risen from less than 50 years in the 1950s to 72.6 years today. However, people's pursuit of the limit of life expectancy has never stopped: what is the theoretical maximum life expectancy of human beings? Can modern science bring us closer to this limit?
Image credit: 123RF
Regarding the limit of human lifespan, there was a widely influential academic debate 5 years ago.
In 2016, The Journal of Nature published a paper titled Animalization for a limit to human lifespan. Scientists from the Albert Einstein School of Medicine in the United States have analyzed the age of death in the long-lived population of France, Japan, the United States and the United Kingdom over the past half-century or so and found that this number stabilized at the end of the last century, indicating that humans are approaching this upper limit of lifespan.
From this, the authors of the paper combined with statistical analysis to put forward a controversial point: the average maximum life expectancy of humans is 115 years, while the upper limit of human life expectancy is 125 years.
▲ This study proposed through statistical analysis that the limit of human lifespan is 125 years (Image source: Reference [1])
Immediately after the paper was published, it received a lot of attention, discussion and questioning. Eight months after the publication of the paper, the journal Nature simultaneously published five short articles, and a number of scientists studying aging questioned the study from the perspectives of data selection, statistical methods and inferences, and the authors of the original paper responded accordingly. For such a fierce academic debate, Nature has no reason to choose to retract, but it is rare for a Nature paper to encounter such a large-scale opposition.
Compared to the study's pessimistic conclusions, the upper limit of life proposed by a new study this year is much more optimistic. Scientists at Singapore-based biotechnology company Gero have built an index of an individual's resilience from biomarkers in the blood.
This index shows that the older the age, the weaker the individual's ability to recover. And when the age is between 120 and 150 years old, there will be a tipping point - once this age is crossed, the human body completely loses its ability to recover, and death is imminent. According to the study, published in Nature Communications, the theoretical maximum lifespan that humans can achieve is 150 years, which means that we are far from the limit.
▲Schematic diagram of human aging trajectory (Image source: Reference[2])
What is the theoretical maximum lifespan of human beings? It can be seen that the research so far is far from agreed, and it has not formed a widely recognized research method. But whether at 125 or 150, humans have not reached this upper limit. So, have scientists found a way to slow down aging and reach the limit of lifespan?
It can be said that in the various model animals in the laboratory, we have found countless clues to longevity. For example, in mouse experiments alone, researchers from various countries have achieved the reversal of aging with many different ideas:
Blood from young mice was transfused to old mice, and extracellular vesicles in the plasma of young mice reversed the aging process of old mice;
The use of different drugs and plant extracts to remove senescent cells in the body of elderly mice also played a life-prolonging effect;
After using drugs to repair inflammation and other problems caused by the "leakage" of the blood-brain barrier, the brains of old mice also became younger...
On the other hand, some unusually long-lived animals also provide us with an incision to delay aging. Not long ago, a Science study found multiple genes associated with longevity in rock fish that can live 200 years in the Pacific Ocean. As the "longevity star" of the animal kingdom, naked mole rats contain abnormally high hyaluronic acid in their bodies, which may be the reason why they are not cancerous; the mechanism that they may not age until they die is also waiting for us to discover.
As for whether these fruitful results from animal experiments can eventually be translated into therapies for humans, it remains to be verified. But for those of us who are reading this article, the life limit seems too far away. After all, most people die from other causes before the "natural aging" process determines our longevity. So perhaps the more meaningful answer than to expect the advent of "longevity pills" is simpler: start with daily habits to reduce the risk of underlying diseases while making the brain younger.