What is REM Sleep Behavior Disorder?
REM Sleep Behavior Disorder (RBD) is a parasomnia characterized by the loss of normal muscle paralysis during REM sleep, causing patients to physically act out their dreams with potentially violent and injurious movements. 1
Core Pathophysiology
During normal REM sleep, the body experiences complete skeletal muscle paralysis (atonia) while the brain is actively dreaming, but in RBD this protective mechanism fails. 1
The loss of REM atonia results from dysfunction in brainstem structures (pontine tegmentum and medulla) that normally suppress muscle activity and locomotor generators during REM sleep. 2, 3
Polysomnography demonstrates either sustained muscle activity (tonic activity) present in >50% of REM epochs with elevated chin EMG, or excessive transient muscle bursts (phasic activity) during REM sleep. 4, 1
Clinical Manifestations
Contrary to classic descriptions, most movements in RBD are actually discrete and seemingly benign—small twitches and brief jerks primarily affecting the extremities that occur every few seconds to minutes. 4
Complex and potentially dangerous dream enactment behaviors (punching, kicking, leaping from bed) can occur at any point during the night or disease course. 4
Vocalizations are common, including talking, laughing, shouting, or screaming during sleep episodes. 4
Patients often experience distress upon awakening after an episode, questioning whether they have a psychological condition. 4
The behaviors are typically violent and associated with violent dream content, posing serious injury risk to both the patient and bed partner. 2
Epidemiology and Risk Factors
RBD affects approximately 80 million patients worldwide, making it a common condition. 4, 5
Age is the single greatest risk factor—approximately 1 in 20 older adults may have RBD, with typical onset in the sixth or seventh decade of life. 4
The disorder predominantly affects older adults, with an estimated prevalence of 0.4-0.5% in the general adult population. 2
Types of RBD
Isolated (Idiopathic) RBD
Occurs without a clear underlying neurological disorder or inciting medication/substance. 1, 5
Patients with idiopathic RBD have a 70% risk of developing a neurodegenerative α-synucleinopathy (Parkinson's disease, dementia with Lewy bodies, or multiple system atrophy) within 12 years of diagnosis. 4, 6
These patients tend to be younger than those with secondary RBD due to neurodegenerative disease, but older than those with drug-induced RBD. 4
Secondary RBD
Associated with neurodegenerative diseases, especially α-synucleinopathies including Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. 1, 3
Also occurs with narcolepsy type 1. 3
Frequency is much higher in certain neurodegenerative diseases compared to the general population. 2
Drug-Induced/Exacerbated RBD
Most commonly caused by serotonergic antidepressants, particularly selective serotonin reuptake inhibitors (SSRIs). 4, 5
Also associated with tricyclic antidepressants and monoamine oxidase inhibitors (MAOIs). 4
Diagnostic Requirements
Definitive diagnosis requires both clinical history of dream enactment behaviors AND polysomnography with video-audio recording demonstrating loss of normal REM atonia. 4, 3
Time-synchronized video showing actual behaviors corresponding to EMG abnormalities is necessary for diagnostic confirmation. 4
Movements involving distal muscles of hands and face are particularly characteristic of RBD. 4
Clinical Significance and Prognosis
RBD serves as one of the best biomarkers available to predict α-synucleinopathies, with most patients converting to overt neurodegenerative disease approximately 10 years after diagnosis. 6, 7