Why Don’t Bears Get Blood Clots?

Physical activity is one of the most important factors in preventing blood clots. In general, when you can’t move around for a period of time (like after having surgery), your risk for blood clots rises.

But bears spend all winter in a state of hibernation and don’t get blood clots. Humans typically can’t spend months curled up in bed half-asleep without getting clots – so why are bears able to do this?

A recent study published in the journal Science may shed some light on the subject. A Swedish team took blood samples from 13 brown bears who were hibernating in the winter. The researchers later took blood samples from thesame bears during the summer.

They found that the levels of a protein called HSP47 were much higher in the summer, while this protein wasvirtually absent in the winter. HSP47 is involved in the blood clotting process.

In fact, levels of HSP47 are also lower in humans during extended periods of immobility. For example, in people with spinal cord injuries, HSP47 levels fall over time. This finding helps to explain why people who are immobilized for a short amount of time (like after surgery) have an increased risk for clots, while the clot risk is lower than expected in those who are immobile for longer.

It’s hoped that further research into HSP47 will lead to new treatments that can reduce the risk of blood clots. Whether this research will allow humans to spend the winter in hibernation has yet to be determined – but if that’s your dream, we may be one step closer.

*Originally published in The Beat — June 2023. Read the full newsletter here.