Basics of RBD

What is RBD?

RBD, or REM Sleep Behavior Disorder, is a condition where the normal paralysis that occurs during REM sleep fails, allowing a person to "act out" their dreams.

REM Sleep is the stage of sleep where most vivid dreaming happens. Normally, the brain induces a state of paralysis to prevent movement during this stage. In RBD, the system responsible for this paralysis malfunctions, which means individuals can physically enact their dreams.

What are the causes of RBD?

The most common cause of RBD is a group of conditions called synucleinopathies.  These include Parkinson’s disease (PD), Dementia with Lewy bodies (DLB), and Multiple System Atrophy (MSA). In these conditions, certain areas of the brain, including those controlling REM sleep paralysis, undergo premature aging. RBD can often be an early sign of a developing synucleinopathy.

Other, less common causes of RBD include:

• Medications: Certain medications, particularly antidepressants, can trigger RBD. In these cases, symptoms may appear shortly after starting the medication. However, even when triggered by medications, underlying neurodegenerative diseases may still be present, because the medication may have unmasked a milder RBD that was already there.

• Other Neurodegenerative Conditions: RBD can develop in other aging-related conditions, though usually later in the disease course.

• Other Neurological Conditions: Less commonly, RBD can be caused other conditions, such as autoimmune diseases (where the immune system attacks the brain), narcolepsy (a general sleep-state disruption), or a focal lesion (stroke, etc.) that directly damages the REM paralysis center.

What are other causes of dream enactment?

Not all dream enactment is due to RBD. Other causes include:

• Non-REM Parasomnias: These include sleepwalking and sleep talking, which are common and occur outside of REM sleep. Non-REM parasomnias can be thought of a state of being half-asleep/half-awake.  During episodes, people may mumble, talk, get out of bed, and even perform very complex actions. Unlike RBD, non-REM parasomnias are generally not associated with synucleinopathies.

• Apnea: Sleep apnea is a condition where breathing stops intermittently during sleep. It is often most severe during REM sleep. Apnea episodes can lead to partial wakening, during which a person might appear to act out dreams. Apnea is very common, so having apnea does not rule out also having RBD.  

• Other Conditions: A variety of other conditions can occasionally mimic RBD, ranging from the very mild (for example, simple tossing and turning) to more severe conditions such as nocturnal seizures.

Therefore, proper testing is essential to confirm an RBD diagnosis.

What is the diagnosis of RBD?

The primary test for diagnosing RBD is a polysomnogram (PSG). This involves an overnight stay in a sleep lab. The test monitors sleep stages, breathing, heart rhythms, and brain activity. Muscle activity is also recorded to assess whether the system responsible for paralysis is functioning during REM sleep. If the system is no longer working, the diagnosis of RBD can be made.

Polysomnograms, particularly those measuring the REM atonia system, are complex and are best performed in specialized sleep labs with expertise in RBD. Research is ongoing to make this diagnosis simpler.

What is the treatment of dream enactment?

The main concern with RBD is the risk of injury, so treatment focuses on creating a safe sleep environment. Suggestions include:

• Protecting bed partners (even sleeping alone if necessary).

• Removing sharp or breakable objects from the bedside.

• Ensuring the bed is not too high and placing padding nearby in case of falls.

If safety is ensured and sleep quality is otherwise good, medication may not be needed. For more intense or disruptive movements, medications like clonazepam or melatonin are commonly used. Melatonin, a natural hormone that regulates sleep/wake cycles, may help reduce activity somewhat. It generally has few side effects, but its effectiveness is not fully clear. Clonazepam likely does reduce acting out of dreams, although it can be associated with daytime sleepiness and poor concentration. Other medications may be useful and can be discussed with a healthcare provider if needed.

What is RBD and Risk of Synucleinopathy?

Since synucleinopathies are the most common cause of RBD, many people with RBD are eventually diagnosed with one of these conditions. In worldwide studies which combined all people with polysomnogram-diagnosed RBD together, about 6-7% (or, about 1 in 15) ‘converted’ to Parkinson’s, DLB, or MSA each year.  

However, the time to progression varies, and can be quite long.  Other factors, like older age, a loss of the ability to smell, constipation, low blood pressure upon standing, motor slowing, and mild cognitive issues, can help predict the likelihood of progression. One of the primary goals of the NAPS study is to identify more reliable markers for predicting risk and monitoring progression.