Wednesday, December 28, 2022
Web Desk

Could humans hibernate and 'sleep through' winters?

Evidence shows early humans may have survived harsh cold by sleeping through winter

Web Desk
Image shows a man sleeping on his arm.— Unsplash
Image shows a man sleeping on his arm.— Unsplash

Humans typically sleep a little bit more during the winter. Reduced light exposure directs the body to create the hormone melatonin, which promotes sleep. But what if people could actually hibernate?

Some experts think it might be closer than we think and it could have a variety of advantages, such as reducing the risk of cardiac arrest and stroke, averting famine, and even permitting space flight.

Hibernation in dwarf lemurs has been investigated by Dr Marina Blanco, a research scientist at Duke University in the United States. She told Good Health that inducing hibernation in people may be more science than fiction.

"It could help us to survive “energetic crises” — for example, seasonal lack of food — and to cope with serious injury by avoiding organ damage and increase longevity," she was quoted as saying.

When it comes to injury, the concern is that abrupt blood flow restoration to tissue after its supply had stopped, such as after a heart attack or stroke, might result in deadly injuries.

Dr Michael Ambler, a clinical lecturer at Bristol University who divides his time between working in intensive care and investigating animal hibernation, said studies with mice have shown that if you keep them cool when the blood flow returns "then this trauma is hugely reduced."

According to him, being cold "reduces metabolic activity in mitochondria, which are essentially power stations within the cell."

"When the blood returns, the mitochondria rapidly reactivate, and this generates by-products that can be harmful. By slowing down the rate at which they switch back on after blood flow returns, hypothermia protects the vital organs from this explosion of activity."

Hedgehogs, bats, and brown bears are well-known examples of creatures that enter a state of hibernation, which is characterised by little activity, a slowing of metabolic processes, and a reduced need for oxygen. Depending on the species, it might persist for days, weeks, or even months, enabling these animals to withstand periods of cold and scarcity.

Similar, although shorter, states of torpor are experienced by other animals, during which the body's core temperature, heart rate, respiratory rate, and metabolic rate all drop.

Torpor, however, appears to be an involuntary state that an animal enters when they need to preserve energy, for example, when food is in short supply, in contrast to hibernation. Small rodents like mice and hamsters as well as a lot of birds frequently go into torpor.

Animals aren't the only ones who do this, though. Bones found at Sima de los Huesos, or "the pit of bones", provide evidence that hundreds of thousands of years ago, early humans may have survived the harsh cold by sleeping through the winter.

According to a research study that was published in the journal L'Anthropologies, the fossils in the cave exhibit seasonal changes that indicate bone formation was disrupted for a number of months out of the year.

According to the researchers, these prehistoric people were in "metabolic states that enabled them to live for lengthy periods of time in freezing temperatures with limited sources of food and enough stores of body fat." 

Despite the fact that humans no longer hibernate or enter into torpor, mounting evidence points to the possibility that we still possess the necessary biological components.

Blanco explained: "Humans, like other mammals, may already have the biological “machinery” to hibernate, but we need to figure out how to activate, regulate and coordinate all the necessary processes."

Even now, there are monkeys who still engage in this behaviour, which appears to be widespread and ancient. Dr Blanco has successfully reactivated the ability to hibernate in dwarf lemurs by carefully managing the temperature of their enclosure decades after they had lost the habit due to life in captivity.

Similar to humans, dwarf lemurs are warm-blooded primates that live in Madagascar in the wild. However, when they hibernate, they can lower their body temperature and slow their metabolism to the point where they only need 2% of the energy that they typically would.

Using genetically altered viruses to activate the region of the brain that causes torpor in mice, Ambler's tests have caused torpor in rats, which ordinarily don't enter this condition, further indicating that it may be feasible to cause it in other species.

"Increasingly, scientists are considering whether we could harness components of hibernation for clinical benefit," he added.

Although "therapeutic hypothermia" — when the body is chilled after a catastrophic injury or cardiac arrest — had been widely used in hospital intensive care units since 2002, it's now not used as frequently. It is thought to slow down metabolic processes including the breakdown of glucose in cells, lowering the quantity of oxygen the brain needs to operate, and postponing the death of brain cells.

But this comes with risks. These include increasing blood sugar levels, causing an irregular heart rhythm, and decreasing blood's ability to coagulate, which could result in bleeding.

Although more recent studies have failed to display any benefit, it is nevertheless used in premature babies who have suffered brain damage during delivery.

In addition, both the European Space Agency (ESA) and NASA are keenly interested in this field of study. Earlier this year, a study sponsored by the ESA revealed that human hibernation might develop into a "game-changing" method for space flight.