Sleepwalkers don't feel pain during sleep
Sleepwalking, also known as somnambulism, is a fascinating sleep phenomenon. Patients have told me all kinds of stories about their sleep adventures throughout the years. Many never have a clue that they walk in their sleep until a bed partner brings it to their attention. Some figure out that they may be getting up to eat during the night when they find crumbs in their bed or food left out on counter tops with no one else in the house. On more than one occasion, patients have noted that waking up with cuts and bruises but no idea how they got them. Interestingly, I have had many men talk about the strange places they have urinated when sleepwalking, including one refrigerator.
Sleepwalking occurs in about 4% of adults and 17% of children. It occurs most often during the first third of sleep in non-REM stages 3 and 4. A family history is a good predictor of whether a child will develop parasomnia. Sleep deprivation is a major trigger. Foods can also trigger an event. Recently a patient told me that his mother recalls that the only time he walked in his sleep was when he ate lemon pie. And as providers, we have likely all heard stories of patients who have done strange things in their sleep while taking hypnotics for insomnia.
Researchers recently reported that patients who walk in their sleep appear to have decreased pain perception in sleep. Along with controls, 100 adults with previous histories of sleepwalking participated in the study. Headaches and migraines appeared to be more prevalent in the study group. Of the one 100 sleepwalkers, 44 individuals suffered from chronic pain. The sleepwalkers were also more likely to have insomnia, depression, and hypersomnia than the control participants. Forty-seven of the patients noted at least 1 injurious episode in their somnambulism history; pain only woke 10 of the patients. In contrast, the other 37 (78.7%) participants perceived no pain during an injurious episode until they woke later in the night or in the morning. One patient reported that he had climbed to the roof, fell, and broke his leg, but did not awaken until the morning.
It is not clear why pain perception is different during sleepwalking episodes. Other studies have shown that sleep deprivation can reduce the pain threshold. It is interesting that sleepwalkers often have increased pain complaints when awake but decreased pain during sleepwalking. One theory, as noted by the researchers, is that "activity inhibition mechanisms within the thalamocortical circuits may block the transfer of sensory information to the cerebral cortex, thus inducing analgesia."
As more studies are completed, perhaps we will learn more about this interesting sleep abnormality. In the meantime, I'll be interested to hear the stories of those who pace about in their sleep.
- Lopez R, Jaussent I, Dauvilliers Y. Pain in sleepwalking: a clinical enigma. SLEEP 2015;38(11):1693–1698.