Muscle Paralysis During Rem Sleep: What You Need To Know

During REM sleep, the body experiences temporary paralysis of most muscles, excluding those that help with breathing, digestion, and some eye movements. This paralysis, known as atonia, is caused by two powerful brain chemical systems that work together to paralyze skeletal muscles. The neurotransmitters gamma-aminobutyric acid (GABA) and glycine cause REM sleep paralysis by switching off the specialized cells in the brain that allow muscles to be active. This prevents injury and allows us to dream quietly and safely throughout the night.

What is REM sleep?

Sleep is generally divided into two stages: REM (rapid eye movement) and NREM (non-rapid eye movement). NREM is further divided into three parts: starting to fall asleep, light sleep, and deep sleep. During deep sleep, your breathing slows down, your blood pressure drops, and your energy is renewed.

During a typical night, your sleep alternates through cycles of REM and NREM sleep about every 90 minutes. The REM stage accounts for approximately 25% of sleep time, while the NREM stage takes up the other 75%. If you get the recommended seven to nine hours of sleep each night, you might move through five to six full sleep cycles.

During the REM stage of sleep, your eyes move rapidly, darting back and forth under your closed eyelids. It is during this state that most of your vivid dreaming takes place. At the same time, your muscles become temporarily paralysed, so you don't act out your dreams. This is called REM sleep muscle paralysis or muscle atonia and is considered a normal function of REM sleep. Dreaming occurs during REM sleep because there is more brain activity than during the NREM stage, and it is considered a more wakeful state, as your heart rate and blood pressure increase to levels close to what you experience when you are awake.

REM sleep is important because it stimulates the areas of your brain that help with learning and memory. During this stage, your brain repairs itself and processes emotional experiences. It also transfers short-term memories into long-term memories. Lack of REM sleep can cause trouble coping with emotions, trouble concentrating, a weakened immune system, and grogginess in the morning.

To increase your REM sleep, you need to get more sleep overall. You can improve your sleep by creating a relaxing bedtime routine, setting a sleep schedule and sticking to it, avoiding nicotine and caffeine, and exercising and spending time outside every day.

What is sleep paralysis?

Sleep paralysis is a temporary condition in which a person is unable to move any part of their body right before falling asleep or upon waking up. It occurs when the body is stuck between sleep phases, typically during the rapid eye movement (REM) sleep stage. During sleep, the brain sends signals to relax the muscles in the arms and legs, resulting in muscle atonia, which helps maintain stillness during REM sleep. However, in sleep paralysis, the person remains conscious and aware of their surroundings, creating a frightening experience.

Episodes of sleep paralysis can last from a few seconds to a couple of minutes, and they can be quite distressing. During an episode, individuals may experience hallucinations, a sense of suffocation, or feelings of pressure on their chest. It is important to note that sleep paralysis is not typically dangerous, but it can cause emotional distress. Approximately 30% of people worldwide will experience at least one episode of sleep paralysis in their lifetime, and it can occur at any age.

Sleep paralysis is often associated with other sleep disorders, such as narcolepsy, cataplexy, and hypnagogic hallucinations. It can also be linked to certain conditions, including increased stress, excessive alcohol consumption, sleep deprivation, and mental health disorders such as anxiety, bipolar disorder, post-traumatic stress disorder (PTSD), or panic disorder. While there is no treatment to stop an episode once it starts, treatments are available to reduce the frequency of episodes. These treatments may include medications to prevent REM sleep or to address underlying mental health conditions or sleep disorders.

What is REM sleep behaviour disorder?

REM sleep behaviour disorder (RBD) is a parasomnia involving dream enactment behaviour associated with a loss of muscle atonia during REM sleep. During normal REM sleep, a person's muscles are relaxed, and they are unable to act out their dreams. However, in RBD, the individual maintains some muscle tone, allowing them to move and act out their dreams. These movements can range from minor twitches to very complex and violent behaviours that can cause injury to the individual or their bed partner.

RBD is often associated with antidepressant use and has a strong correlation with neurodegenerative diseases, particularly Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. It is more common in elderly individuals and males. Diagnosis of RBD requires confirmation through a sleep study, which helps to identify abnormal behaviours during REM sleep and rule out other sleep disorders.

The primary goal of RBD treatment is to reduce the risk of injury to the patient and their bed partner. This may involve changing sleep habits, such as lowering the bed or separating the sleeping partners. Pharmacological treatments, such as melatonin, clonazepam, or pramipexole, are also recommended to help reduce symptoms.

How does muscle paralysis occur during REM sleep?

During REM sleep, the body experiences temporary paralysis of most of its muscles, while the brain remains active and dreaming. This paralysis, also known as muscle atonia, is considered a normal function of REM sleep and is thought to prevent sleepers from acting out their dreams and causing potential injury to themselves or their bed partner.

During REM sleep, the brain sends signals that relax the muscles in the arms and legs, resulting in muscle atonia. This process is mediated by two powerful brain chemical systems, involving the neurotransmitters gamma-aminobutyric acid (GABA) and glycine. These neurotransmitters work together to "switch off" the specialised cells in the brain that allow muscles to be active, causing REM sleep paralysis.

In individuals with REM sleep behaviour disorder, this normal muscle paralysis does not occur, allowing them to physically act out their dreams. This can range from minor movements such as leg twitches to more complex and violent behaviours that can cause serious injury.

The exact cause of REM sleep paralysis is not yet fully understood, but it is believed to be related to the interaction of various neurotransmitter systems in the brainstem, forebrain, and hypothalamus.

How is REM sleep linked to other disorders?

During REM sleep, the body experiences muscle atonia, or temporary paralysis, which is considered a normal function of REM sleep. However, in REM sleep behaviour disorder (RBD), the body does not enter this state of paralysis, allowing sleepers to act out their dreams, which can result in injury to themselves or their bed partners. RBD is a parasomnia, or sleep disorder, that disrupts sleep and can be caused by antidepressants, as well as being linked to other neurological disorders.

RBD is characterised by abnormal vocalisations, abnormal motor behaviour, and altered dream mentation. The movements involved in RBD can be violent and cause accidental injury, so it is important to seek treatment. Treatment focuses on creating a safe sleeping environment and may involve medications such as melatonin, clonazepam, and pramipexole.

RBD is associated with neurodegenerative disorders, particularly Parkinson's disease, Lewy body dementia, and multiple system atrophy (MSA). These conditions are called alpha-synucleinopathies and are linked to lesions in the pons region of the brainstem. About 97% of people with isolated RBD will develop one of these conditions within 14 years of their RBD diagnosis.

In addition to its links with neurodegenerative disorders, RBD can also be caused by certain medications, such as antidepressants, and other sleep disorders like narcolepsy. Obstructive sleep apnea (OSA) can mimic RBD and is referred to as "pseudo RBD."

Sleep paralysis, another sleep disorder, is also linked to REM sleep. It occurs when the body is stuck between sleep phases, unable to move temporarily before falling asleep or upon waking up. Sleep paralysis can be caused by sleep deprivation, irregular sleep schedules, obstructive sleep apnea, and mental health conditions. While not dangerous, it can cause emotional distress.

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