When someone is sleepwalking they’ll move out of bed and show complex behaviours while lacking high-level cognition (such as planning). They’re also likely to have their eyes open and may be staring vacantly, which can be disconcerting to anyone they encounter.
Sleepwalking, also known as somnambulism, involves a partial arousal from deep sleep. This typically occurs during the Non-Rapid Eye Movement (NREM) stage of sleep. This type of sleep predominates during the beginning of the night, which is why sleepwalking typically happens at this point.
Children are more likely than adults to sleepwalk due to the composition of their sleep. Overall prevalence rates of sleepwalking vary widely, but one meta-analysis estimated as many as 7 per cent of people sleepwalk.
As to whether it’s dangerous to wake a sleepwalker, it’s not advisable to do this forcefully as this could lead to disorientation or even a violent response from the sufferer. However, in certain circumstances, it may be appropriate to gently wake someone who has completed a sleepwalking episode and let them fall back to sleep again in order to prevent them from moving straight back into another sleepwalking episode.
If you discover a sleepwalker, rather than waking them, you might want to calmly lead them back to their bed in order to help ensure their safety.