Typically found in the starry realms of sci-fi movies, human hibernation could be set to make its way from the silver screen to the world of reality. And the possibilities for humans are huge – but what exactly is human hibernation, what are the benefits, and just how close are we to it being achieved?
To understand how humans could hibernate, we need to take a look at our mammalian brothers and sisters who do the same.
Simply put, hibernation is a long, dormant state where bodily processes slow down to conserve energy and reduce the need for nutrition. It typically lasts through the cold months of winter when food is less available and temperatures more difficult to deal with. To help animals survive the cold months without food, the effects of hibernation include:
While this may all look very similar to how the human body reacts during sleep, hibernation is much more extreme. Where human body temperature decreases by a degree or two overall during sleep, animals experience a much greater drop during hibernation.
Take black bears, for example:
“A black bear…can lower its temperature—generally about 91 degrees Fahrenheit (33 degrees Celsius)—by…about 9 to 11 degrees Fahrenheit (5 or 6 degrees Celsius), yet bring its metabolism almost to a grinding halt, at 25 percent of the normal rate.
There are more extreme examples too:
“The Arctic ground squirrel of Alaska, Siberia and Canada, for instance, hibernates through seven months of freezing weather, its body temperature dropping to almost minus 3 degrees Celsius! Amazingly, the squirrels’ blood manages to remain liquid, even at these extreme temperatures.”
We’ll touch on the benefits of human hibernation later, but for it to be a worthy process, our bodies would need to undergo similar changes. A key component would be the reduction, to a near halt, of our metabolic rate. This would ensure that the energy stored in bodily fats would be directed only to the most essential physiological functions.
Until recently, the closest we’d come to understanding whether human hibernation would be possible were studies into cryogenic sleep. However, more recent studies and experiments into animal hibernation and torpor have led to what could be considered a breakthrough.
Torpor definition:
Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability.
Source: Wikipedia
The key differences between hibernation and torpor are:
So, now we know what torpor is, let’s get back to why it’s become an important part of the journey towards human hibernation.
A 2023 study, published in Nature Metabolism, reported the successful induction of a “torpor-like…state in rodents.” Not only did this study result in mice being placed into such a state through ultrasound stimulation, it also did the same in rats – a species that don’t naturally hibernate.
“Our findings demonstrated that ultrasound stimulation…suppressed physiological processes in a manner that resembled natural torpor. Ultrasound stimulation systemically suppressed metabolism and thermogenesis, switched energy substrate utilization to fat and decreased heart rate, which collectively are key features of natural torpor.”
In short, this is one of the first times humans have been able to instigate such a state manually. And, while it’s likely still some way off for humans, the fact that the same or a similar approach could be applied to humans has caused the scientific community to take note!
Another study looked into the technology that would be required to keep humans in hibernation during space flight. This was completed by the European Space Agency and other prominent researchers. Not only was it concerned with the technology required to keep humans safe during hibernation, but it also looked into the benefits hibernation would have in reduced weight for oxygen, food, and other space travel essentials.
“It focussed on the biology of hibernation in reducing metabolism…and its links to the infrastructure and life support. We concluded that torpor of crew members can reduce the payload with respect to oxygen, food and water but will require monitoring and artificial intelligence (AI) assisted monitoring of the crew”.
Other research into the matter has concluded that while humans don’t currently hibernate, our ancestors may have had the ability to snooze their way through winter. As quoted in the New Scientist, Sandy Martin of the University of Colorado, identifies why it’s our mammalian status which leads scientists to believe human hibernation will one day be possible.
“The distribution of hibernating species on the tree of mammals makes the likely conclusion that the common ancestor of all mammals was a hibernator. It’s possible we all have the genetic hardware.”
Like in those intergalactic movies – think Space Odyssey 2001, Avatar, and Passengers – the biggest advantage of human hibernation is space travel. Even just travelling to Mars, our closest neighbour, would take 7 months, so the ability to put humans into a reduced state of consciousness would greatly help for all of the aforementioned reasons.
And for galaxies beyond our own, it becomes even more important! That’s because journeys outside of our own galaxy would require lengths of time way beyond the human lifespan, as identified by NASA:
“To get to the closest galaxy to ours, the Canis Major Dwarf, at Voyager’s speed, it would take approximately 749,000,000 years to travel the distance of 25,000 light years! If we could travel at the speed of light, it would still take 25,000 years!”
Clearly, for those longer trips, it’s likely that even full hibernation wouldn’t suffice. But for the shorter trips, animals have been known to hibernate for similar periods. And with modern science, even a lighter torpor could suffice. Whether that’s in the form of an elongated period or going in and out of torpor for a day or two at a time.
Either way, recent experiments have shown progress towards a procedure allowing for less nutrition and oxygen during space travel.
Perhaps more interestingly, scientists believe that one of the biggest benefits would be the impact these states have on stress. It’s believed that inducing torpor or hibernation would help prevent boredom and other “stressors” that come with being awake!
Beyond space travel, humans could benefit more directly from the possibilities of hibernation. For example, take a look at this quote from the European Space Agency:
“Mimicking therapeutic torpor, the idea of putting human into a state of hibernation has been around in hospitals since the 1980s – doctors can induce hypothermia to reduce metabolism during long and complex surgeries. However, it is not an active reduction of energy and misses most of the advantages of torpor. Studies on hibernation to visit other planets could offer new potential applications for patient care on Earth.”
They continue by stating that “if a person spends six months in bed, there is a major loss of muscle, bone strength and more risk of heart failure.”
Bears, on the other hand, experience minimal reductions in muscle mass and tissue damage. It seems that hibernation prevents the atrophy of muscle and bone that comes with humans being out of action for such a time.
So, the ability to put humans into hibernation could have major implications for medicine. From brain damage to heart attacks, there’s a real need in the medicinal world to be able to place the body into stasis. By slowing the body’s processes beyond the means of current science, into a hypometabolic state, we may be able to ensure organs don’t deteriorate during surgery or long periods of inactivity.
Surprisingly, a similar scenario has been played out before. Check out this article from The Guardian about Mitsutaka Uchikoshi, who went missing on Mt Rokko in western Japan.
Choosing to walk down the mountain instead of taking a cable car, he slipped, broke his pelvis, and ended up on the mountain for 24 days, until a passing hiker discovered his body.
After his fall, it’s believed he lost consciousness and his body, responding to the freezing conditions, pushed him into a state of hibernation.
“He fell into a state similar to hibernation and many of his organs slowed, but his brain was protected,” Dr Shinichi Sato, head of the hospital’s emergency unit, told reporters. “I believe his brain capacity has recovered 100%.” Doctors said they did not expect him to experience any lasting ill-effects.
It remains unclear how, but he had a barely discernible pulse, and his metabolism dropped to an extremely low rate, similar to that of hibernating animals. Speaking to the Associated Press, Hirohito Shiomi, a professor at Fukuyama University, said:
“This case is revolutionary if the patient truly survived at such a low body temperature over such a long period of time.”
Despite recent research, it’s unlikely that we’ll be able to instigate human hibernation at any time soon. New studies may have taken the concept from a sci-fi fantasy into the realm of possibility, but there’s still some way to go. However, take confidence in the fact that multiple advances have been made.
This includes studies into our genetic heritage and how our ancestors may have been able to hibernate, to scientific experiments which successfully induced states of torpor in animals that don’t naturally sleep through winter.
In fact, confidence in the field is so high that space agencies are beginning to deliberate on what types of technology would be needed to support such progress. As a parting gift, here’s an example of what a human hibernation-friendly space pod could look like:
