Like somnambulant superheroes on the rampage, sleepwalkers feel no pain as they stalk the night, bumping into things or even unfortunately leaping from tall buildings (really) without waking. Of course, when they do finally rouse themselves, the pain hits them like normal, and they’re more likely to have terrible headaches than people who stay in bed while they slumber.
A study by Régis Lopez and a team from the Montpelier University in France investigated 100 sleepwalkers (and 100 non-sleepwalkers for control) to compare their daytime pains with their pain while sleeping. The study found that sleepwalkers suffer four times as many headaches and migraines as non-sleepwalkers, but it’s another aspect of the study that’s really fascinating.
“Our most surprising result was the lack of pain perception during the sleepwalking episodes,” Lopez told the American Academy of Sleep Medicine.
Of the 100 sleepwalking subjects, 47 reported having injured themselves while sleeping. Of these, only 10 woke up. The rest said that they had felt no pain, and had continued their relentless shuffling, like zombies intent on brains.
These weren’t just bumped heads or grazed knees, either. One subject jumped out of a third-floor window, sustained multiple severe fractures, but still didn’t wake up and feel pain until later that night, says the study. Another climbed onto his roof, slipped, fell, and broke his leg. Again, no pain until he woke up in the morning.
This self-occurring analgesia appears to be related to a connection between dissociated brain activity and nociceptive dysregulation, or malfunctioning nerve pain. That is, the mechanism behind sleepwalking is also behind switching off pain. This could be a rather useful tool in medicine, allowing doctors and surgeons to forego anaesthetics.
Unfortunately, Lopez’s team’s research didn’t investigate this aspect of the phenomenon.