Is there a chance for humans to slow down or stop aging and thus extend their lifespan?

If we first want to define the personality of the following content and make a summary, then we can summarize it in three sentences:

Is there a chance for humans to slow down aging? Yes!

Can humans extend their lifespan? Yes!

Is it because modern life has slowed down aging that human life expectancy has been increasing? No!

The average life expectancy of human beings has been increasing at a rate of about 3 months per year since the industrial age. The trend in our country is similar, especially since entering the peaceful era, when we can clearly see a sharp increase, and then both men and women have entered a steady growth trend.

The life expectancy curve of people born in different eras. The dark blue is the global average, and the rest are the averages of each continent. Image source: Wikipedia-ODogerall

However, is this steady growth due to better living conditions slowing down our aging rate? Last year, a paper published in Nature Communications made a detailed argument on this issue and came to a negative conclusion.

Among them, the two key parameters used by the researchers are called life expectancy and lifespan equality index (self-translated by the author, no unified translation has been found so far). The former is easy to understand, so let me explain the lifespan equality index. Simply put, this index is used to measure how different the ages of death of different individuals in a population are. If most individuals in a population die at a similar age (for example, because of the law of aging, which limits the upper limit of life expectancy, most of the population dies around 80 years old), then this index will be very high. On the contrary, if death has nothing to do with age, and the risk of death at different ages is similar, then the value of this index will be very low.

Subsequently, the researchers used data from nine different ethnic groups and found that the life parity index and life expectancy were strongly correlated, that is, the longer the life span, the higher the life parity index, and vice versa. Moreover, this trend is not unique to humans. When the researchers expanded the scope of the survey to other primates (such as gorillas, chimpanzees, baboons, etc.), they found the same trend! This is even more convincing, indicating that this trend is not caused by human technology, war and other messy things, but is a natural trend.

Life equality index of different creatures, with humans in gray at the bottom and other primates at the top

Image source: Reference [1]

If so, is the difference in life expectancy between different species or different human races due to differences in aging rates? For example, the difference in life expectancy between Asians and Europeans is due to the different aging rates between the two populations.

According to the results of the data model, the researchers came to a negative conclusion. Because they found that as long as the parameters representing the aging rate were slightly adjusted, the previously discovered correlation between life expectancy and the life equality index would be seriously changed. At the same time, the adjustment of the aging rate could not produce differences between different races and species. However, there are some series of parameters that can well restore the differences between different races/species, that is, early mortality rate!

What does this indicate? It indicates that human life span has continued to increase, not because modern technology and living conditions have delayed aging, but because modern medicine and inventions such as antibiotics have greatly reduced the mortality rate of infants, children and young people (these groups, under natural conditions, are the groups with the highest relative mortality rate).

Well, this is basically the end of the answer to this question. If you are still interested, you can continue reading the following extended content.

Although we know that the continuous extension of our human life span in recent years may not be caused by delaying aging, is there any way for humans to delay aging from an individual perspective (even if they delay aging, they will not necessarily live longer than others)? The answer is - yes! And one of the "typical" cases may even make people's backs chill.

Everyone may have heard of "Bloody Mary", but in fact there is an even more brutal countess in history. Because of the bloody crimes she committed, she was dubbed the "Bloody Countess" and "Female Count Dracula". She was the Hungarian Countess Elizabeth Bathory, who was born in 1560.

Portrait of Countess Bathory Image source: Wikipedia

Legend has it that in order to keep herself young forever, the countess bathed in the blood of pure girls and drank at least half a liter of blood before each bath, which she even called "internal washing". She killed at least two girls every time she took a bath. It is said that over 650 girls were killed during the long dark 50 years. Over the decades, more and more girls disappeared near the castle. She was not investigated until a girl who escaped accused her of imprisonment and murder.

But can young blood really fight aging? This rumor comes from an experiment that began in the 1950s. The experiment was originally intended to study parabiosis - scientists found that after connecting the circulatory systems of old mice and young mice, the health of some old mice improved and even extended their lifespan. But it is hard to say that this is due to the blood, after all, the circulatory systems of the two mice are connected together, and we certainly have reason to suspect that it is caused by contact with the healthy organs of the young mice.

Infusing old mice with blood from young mice extends their lifespan

Image source: https://www.nature.com/articles/517426a

Moreover, in subsequent experiments, scientists also found that some mice often died quickly, with a mortality rate as high as 16%. In addition, recent experiments have shown that transfusing young people's blood seems to increase the risk of death in the elderly (of course, other experiments have said that no signs of increased risk have been found).

However, the scientific understanding of this should be: this experiment has only been conducted on mice, and any claim that young human blood can help fight aging is unproven. This method has great uncertainty and ethical issues, and there is no safety guarantee at all - the substances in the blood are too complex, and various viruses or other pathogens may lurk. Transfusing this blood may infect new diseases. Some researchers even believe that fighting aging in this way will increase the risk of cancer.

Of course, precisely because this rumor is very persuasive, it has a huge potential market. Not only have many related papers been published recently, but it has also been welcomed by many scammers. In the United States, some companies once appeared, under the guise of doing experiments, providing young blood to people in need, at $8,000 per unit of blood. These "experiments" had no control groups at all, and anyone could participate in the "experiments" as long as they paid money.

The scientific community in the United States directly denounced this experiment as a new-age fake drug scam, and the U.S. Food and Drug Administration (FDA) directly stopped this behavior.

FDA’s warning message on Twitter Image source: Twitter screenshot

Do I suggest that you have a blood transfusion? Of course not! Why do I mention this? Because the mechanism of blood transfusion in anti-aging, as more and more research results show, may be related to exercise! For example, in one paper, researchers found that when they divided old mice into two groups, A and B, and put an exercise wheel in the cage of the mice in group A to force them to run regularly, while the mice in group B were left alone and allowed to be lazy, after a period of time, the health of the mice in group A was significantly better than that of the mice in group B, especially their brain reactions, and many abilities even recovered to the level of young mice.

After exercise, the mice in group A became healthier

Image source: Reference [2]

Even more surprising is that the researchers found that after the plasma of group A mice was transfused into group B mice, the brains of group B mice improved to the same extent as those of mice that had exercised! Could this be the legendary saying, "If you sit at home, wolfberries will come to you?" This result immediately pointed to a direction, that is, it is possible that exercise activated some anti-aging substances in the blood, which enabled the anti-aging ability to be transferred.

After a lot of trouble, the researchers finally found a protein called GPLD1, which is produced by the liver and can enter the blood circulation. They found that the content of this protein was higher in Group A and young mice, and this protein also increased in the bodies of elderly people who exercised for a long time. In addition, the researchers also found that if the liver of Group B mice overproduced this protein, it would indeed have an anti-aging effect.

Are you having a brain orgasm after seeing this? Just think about it, you can lie in bed, drink fat house happy water, and watch American TV series. As long as you take a shot of GPLD1 from time to time, you can stay young forever. . . . The picture is too beautiful and I dare not look at it.

However, this result is still a long way from final application. After all, there are many obvious omissions that have not yet been resolved.

for example:

Is it only GPLD1 that has the anti-aging effect? ​​Does it also depend on other components in the blood?

Does excess GPLD1 have other side effects on the body?

Even if GPLD1 can restore brain function, will it accelerate the aging of other organs, such as the liver?

So, the imagination is very good, but facing the harsh reality, everyone should work harder and exercise more. After all, you can save money, isn’t that great?

References:

[1] Colchero F, Aburto JM, Archie EA, et al. The long lives of primates and the 'invariant rate of aging'hypothesis[J]. Nature communications, 2021, 12(1): 1-10.

[2]Horowitz AM, Fan X, Bieri G, et al. Blood factors transfer beneficial effects of exercise on neurogenesis and cognition to the aged brain[J]. ence, 2020, 369(6500):167-173.

Produced by: China Science Expo x Zhihu

Author: Haohaohao (Excellent Answerer of Biology on Zhihu)

The article only represents the author's views and does not represent the position of China Science Expo

This article was first published in China Science Expo (kepubolan)

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