REM sleep behaviour disorder is characterized by the occurrence of motor behaviours during REM sleep, in contrast to sleepwalking, which occurs earlier, during the slow-wave sleep phase.
Usually, the body is unable to move during REM sleep. A person with this disorder does not experience this muscle atony and may exhibit behaviours, often violent, that usually reflect what they are dreaming about. They may start talking, shouting, gesticulating and even kicking. When they are awakened they may remember, for example, that they were trying to save someone in danger.
REM sleep behaviour disorder can be due to the use of antidepressants, alcohol withdrawal or sedative medications. It can also be associated with neurodegenerative illnesses such as Parkinson’s disease, or have no specific cause. Affecting around 0.5% of the population, it most often appears after the age of 50, especially in men (87% of cases).