Rapid eye movement (REM) behavior disorder, also known as dream-enacting behavior, is a rare sleep disorder, or parasomnia, which involves acting out vivid, bad dreams during REM sleep by making verbal sounds along with often violent limb movements. REM behavior disorder can be associated with other neurological conditions, such as Lewy body dementia, Parkinson’s disease, or multiple system atrophy, and can occur with other sleep disorders, such as sleep apnea, periodic limb movement disorder, and narcolepsy, and usually occurs in men over the age of 50. REM behavior disorder may worsen over time. REM behavior disorder may also be related to other conditions, such as sleep deprivation, certain medications, alcohol withdrawal, brainstem tumors, and stroke.