Can humans hibernate, too? How long can we “hibernate” in a healthy state?

January 20, according tomedia reports, complaining about the cold winter is one of the few security topics when chatting. Some people may object, saying they like the feeling of freezing their feet, but most people will be happy to curse cold air a few words. In addition to the heating widely used in homes, office buildings and vehicles, new industrial technologies are helping us combat the winter chill. Moisturizing skin care is considered the only way to keep your skin intact at low temperatures, while heavy down jackets are essential for even a few minutes outdoors. Simulating the sun’s electric lights, as well as vitamins, can help us stay optimistic about winter life.

Winter after year is like a protracted struggle, draining the vitality of the whole city. Perhaps we can consider a more comprehensive choice. Our brains and bodies tell us that we probably shouldn’t be having a hard time. Perhaps it’s easier and more efficient to “shut down” and reserve energy for a better month. In other words, we can consider learning from some animals and hibernating.

Of course, human hibernation needs to be social and economic, but in terms of physical function alone, hibernation is not as impossible as previously thought. A handful of scientists are seriously studying human hibernation, including its basic mechanisms, and are looking at future applications such as protecting severely injured patients without pulses, traveling in deep space, and changing metabolic rates to help people lose weight.

Kelly Drew, a professor at the Arctic Biology Institute at the University of Alaska, says human hibernation is actually feasible. Drew studied Arctic ground squirrels, who hid in caves eight months of the year, and the essence of hibernation was body temperature regulation. Lowering the body’s core temperature leads to a “slow” state of low metabolism, in which animals hardly need food. As “warm-blooded animals”, most of the calories we consume are used to maintain body temperature, i.e. to maintain a basic metabolic rate. For example, The Arctic ground squirrels that Drew studied curled themselves up into small balls, and their body temperature plummeted from 37.2 degrees C to -2.7 degrees Celsius, reducing their underlying metabolic rate by about 99 percent.

Even the guinea pigs, which are in the primate category, can reduce their calorie needs by lowering their body temperature to 2%. Unfortunately, humans seem to have a stubborn temperature setting: 37 degrees Celsius. In addition to subtle fluctuations during sleep at night, our body temperature only changes when we have a high fever or hypothermia. The temperature difference of just a few degrees Celsius is likely to mean the difference between life and death.

For a long time, the setting of 37 degrees C was considered immutable, but this may not be the case. Although humans usually don’t enter a state of dullness by their own will – our bodies tremble to prevent it – Drew explains that humans do not lack some kind of “hibernating molecule” or organ. In fact, in extreme cases, doctors can induce patients into a retarded state. For example, surgeons use cryotherapy during a long cardiac arrest to keep the brain and other organs alive for longer without energy available. Cooling is also used in emergencies after cardiac arrest. Covering patients with sedatives with a blanket of circulating cold water is believed to have the effect of applying an ice pack to a sprained ankle, reducing the inflammatory process and minimizing sustained damage to the heart and central nervous system.

Now that cryogenic therapy is widely used in hospitals, some doctors are beginning to believe that this could go a step further and keep people essentially alive after death. At the University of Maryland, surgeon Samuel Tisherman is working on what he calls the “emergency preservation and resuscitation” program. This is an experimental guideline that doctors should quickly cool down patients who suffer from cardiac arrest. According to reports, this can buy time for emergency surgery. Currently, in the case of severe trauma, the patient may have only a few minutes to survive because there is not enough time to be delivered to the operating table. Tissherman cites a man with a gunshot wound to his aorta, who was bleeding quickly. If the person’s heart stops beating, Tissherman’s team will surgically open his chest cavity, massage the heart, let it continue to beat, and repair the aorta. This only takes a few minutes, but it is too late if the patient loses too much blood. The injured man’s brain dies within minutes due to lack of oxygen.

Cooling can extend this critical window period. Even if the heart stops beating, the brain can survive for about two hours at a low enough temperature, Tissherman explains. Inducing the patient into a retarded state in this case means that cooling must be very rapid, requiring a team of anesthesiologists, surgeons and cardiologists to work together with little prior notice. It may seem impossible, but it can be done scientifically. “Technically, these injuries can be repaired,” Tissherman said. “

This raises the question of whether this physiological function can be altered in other ways, clinically or otherwise. If cooling can keep a fatally injured person alive, can this method be used to slow the metabolic process in less extreme cases? How long can a person “hibernate” in a healthy state?

NASA is taking this issue seriously. Since 2014, the agency has funded long-term hibernating research to make long-term space travel a reality. In the case of travel to Mars, for example, the inherent needs of astronauts, such as eating and physical activity, are the main limiting factors, but if their metabolic process can slow down to almost zero, human space travel could theoretically go further. John Bradford, an aerospace engineer who worked with the agency to develop human hibernation methods, says the most obvious benefit is that fewer things are needed. In future interplanetary trips, one crew member can stay awake and the other members hibernate for two weeks. They can lie in small cabins, minimizing the space in the ship that needs to be encased in a radiation shield. The radiation shield is very heavy and requires considerable fuel.

While Bradford’s approach has not really been implemented, he is optimistic. “We can’t find any reason to stop, no impossible reason,” he said. “Of course, the risk of complications is not zero. Because our bodies can’t store food, astronauts have to eat through a tube (surgery to drill a hole in front of the abdomen into the stomach). Mr Bradford says the biggest challenge will be to lower their body temperature while not letting them shake and consume energy. In hospitals, chills were overcome with sedatives, but Bradford’s team was wary of having a group of astronauts take large amounts of sedatives for weeks or months.

Multi-person hibernating capsule effect map for long-term space travel

What we really need is a drug that safely lowers the body’s core body temperature, allowing us to enjoy the “slow” feeling that many other species have. Both Bradford and Tissherman see the drug as a potential breakthrough, a way to address the most obvious constraints in their research. In fact, as a biologist who studies Arctic ground squirrels, Drew has found a drug and believes it will work as well as expected. She describes the drug’s function as “turning down your thermostat.” She used an experimental model of a non-hibernating animal, rats, to show that the drug was effective. Drew is discussing the possibility of human trials with the U.S. Food and Drug Administration (FDA). In 2019, the National Institutes of Health (NIH) provided $11.8 million in funding for her research, suggesting that the treatment’s appeal to humans is not limited to those who are technically dead or astronauts traveling to Mars.

Cooling may play a role in treating many inflammatory diseases, Drew said. She is also interested in the role of body temperature regulation in insomnia. In some cases, sleep disorders appear to be caused by a problem with the body’s standard body temperature cycle every night, so the medication sedating the body temperature can help induce sleep. At the same time, other researchers are studying how obesity and diabetes affect metabolic pathways to temperature dependence and whether they can be reset. As Drew puts it: “To think of body temperature as something we can control is the beginning of a major change in medicine.” “

As for selective hibernation in winter, it is not possible for the time being. In addition to the brain’s temperature setting, humans have some anatomical barriers. For example, Drew points out that her rat’s induced hibernation lasted only two weeks, and then began to develop sepsis, apparently due to a ruptured intestinal wall. Many hibernating animals have anatomically adapted to hibernation, but we humans are different. Black bears’ internal organs are more similar to those of humans, where they maintain hibernation through circulating changes in body temperature, rather than cooling in a straight line for months. Human hibernation may require a similar cycle, which is much more complex than simply shutting down the body’s thermostat with drugs.

The last (apparently fatal) flaw in the human hibernation program is that hibernation is different from sleep and has no obvious recovery effect. Bradford explains that even trying to remain unconscious without damaging the intestines, humans don’t necessarily feel well rested. “I’m sure some people would like to take a weekend, or a week,” he said, “but we don’t know if it’s going to have any therapeutic effect.” (Any day)