Well-Being Medical Advances

Could humans hibernate like bears?

Studying how grizzly bears hibernate could lead to medical advances

Story at a glance

  • In a recent study, researchers studied liver, fat and muscle cells from captive grizzly bears to learn how they change before, during and after hibernation.
  • The biology of hibernation could help preserve human organs for transplant, help wounded soldiers survive injuries and may even one day allow humans to hibernate on long voyages into space.

Not everyone is a fan of winter, and some animals, like grizzly bears, skip it almost entirely by hibernating. When a bear crawls into its den at the start of winter, its metabolism and heart rate each slow to a crawl to conserve energy. 

Other aspects of hibernation seem to bend the rules of the bear’s usual biology. The amount of nitrogen in its blood climbs higher, but doesn’t harm its kidneys or liver. The animal’s body also becomes resistant to insulin, yet blood sugar levels remain stable. 

Bears manage to remain in a kind of sleep for months with no food or water, without the organ damage, diabetes or atrophied muscles that a human might experience under similar biological circumstances. Now researchers are trying to understand the adaptations that facilitate bears’ winter snooze in hopes of harnessing them for new medical treatments, the New York Times reports.   

In a recent study, researchers took liver, fat and muscle cells from captive grizzly bears at different times of year to study how they change before, during and after hibernation. The researchers used DNA samples from the cells as a window into the biological shifts taking place. 

They found that the bear’s organs and tissues each prepared for hibernation differently and that the transition was fluid — not like flipping a light switch. The biggest changes came in the bears’ fat cells, with thousands of genes rising and falling in their levels of expression over the course of the year. Muscle cells, on the other hand, changed very little, remaining active even during hibernation, which may explain how the bears maintain muscle mass despite months of barely moving.

The study highlights that hibernation isn’t as simple as a single hormone that sends the body into a months-long torpor, but that doesn’t mean humans aren’t mining its underlying biology for medicine. 

Researchers studying another hibernator, the thirteen-lined ground squirrel, used one of their biological tricks to help wounded soldiers survive serious injuries when help was a long way off. The researchers created a cocktail that mimicked the squirrel’s blood during hibernation that helps prevent shock due to blood loss and can buy the wounded precious time until help arrives. 

Other potential applications include preserving organs for transplant, and, perhaps many years in the future, allowing humans to travel deeper into space with fewer supplies. Researchers caution that induced hibernation in humans is likely a long way off, but that studying the animals that have mastered this peculiar state of unconsciousness is the only way to find out if it’s possible.