What is REM sleep behaviour disorder, and how is REM a risk factor for Parkinson’s disease?

REM sleep ( rapid eye movements ) is one of the phases of human sleep characterised by loss of body muscle tone and the presence of rapid eye movements (REM). Intermittent persistence of muscle tone during REM sleep is the basis of REM Sleep Behavior Disorder (SRSD). In the periods in which muscle tone (REM sleep without atonia), the subject can express the movement perceived in the dream scenes.

“SRCT is clinically characterised by the presence of abnormal violent dreams and complex, vigorous, problematic or violent behaviour”. This disorder usually concludes, frequently, with the result of injuries.

It is usually more common in men over 50, although it can also affect women.


In almost all women and about 50 per cent of men, the disorder has an origin related to the onset of a neurological disorder, usually a degenerative disease, such as those with Parkinson’s symptoms.

“SRCT may precede the onset of the neurological disease by more than ten years and may also be another manifestation of the motor dyscontrol associated with narcolepsy”.


The main clinical manifestation is the presence of violent dreams in which the patient feels threatened or attacked by people or animals.

During these dreams, the individual can visualise himself defending himself and attacking his aggressors. In those moments, he can also display behaviour, normally brief, complex and vigorous, which causes injuries to both the patient and the bed partner.

Abnormal behaviour includes yelling, name-calling, kicking, and indiscriminate hitting with arms and legs. Upon awakening, there is a rapid return to full wakefulness, and the patient may report a vivid dream with violent content consistent with the behaviour developed.


As the head of the Quirónsalud Madrid University Hospital Sleep Unit points out, there is no known way to identify the disorder’s future development or prevent its appearance.


Although this disorder is usually chronic, there are acute forms, frequently caused by medication (generally antidepressants) or alcohol deprivation and certain sedative drugs.

The acute form is usually short-lived.


The sleep behaviour disorder diagnosis in the REM phase is based on the patient’s report and witnesses.

Based on these testimonies, the specialist can request that a polysomnogram (sleep study) be performed to confirm the diagnosis. This test usually shows that, during REM sleep, muscle tone allows the execution of motor acts (in REM sleep, it is normal for muscle tone to be abolished except in the diaphragm and eye muscles).


This disorder does not have a definitive cure, but some drugs improve patients’ sleep by eliminating these behavioural changes and normalising dreams.

“Clonazepam is the treatment of choice. Doses between 0.5 and 2 mg, administered at bedtime, effectively control abnormal daydreaming and violent behaviour. Other less effective treatments include carbamazepine and melatonin.

The control and progression of the disease are linked to the patient’s lifestyle. For this reason, affected people maintain regular sleep-wake cycles, do not drink alcohol and inform the specialist of any medication, particularly antidepressants, previously prescribed.

Once treatment with clonazepam has been administered, absolute control of symptoms should be expected. However, since this disorder has no cure, the symptoms will reappear if the patient stops treatment.

In cases where this pathology is linked to a degenerative disease of the nervous system, it will continue its progressive course regardless of treatment with clonazepam. However, the degenerative disease requires specific treatment.

When to go to the specialist

Suppose the patient notices that he has dreams with violent content that lead to furniture damage or injury to himself or third parties. In that case, he should go to an expert who will help him confirm the disease and prescribe the appropriate treatment to reduce the intensity of the symptoms.

In addition, if the family notices that during sleep, they emit screams, insults or threatening or coarse phrases and behave aggressively, they must talk to the patient to go to the doctor.

REM is a risk factor for Parkinson’s disease.

The research, coordinated by the neurology consultant of the Multidisciplinary Sleep Unit of the Clinical Hospital of Barcelona Álex Iranzo, has been financed with a grant from the Health Research Fund (FIS). These patients are characterised by being over 50 years old, and because, being in the REM phase, instead of dreaming and being paralysed -as usual-, they have nightmares and scream, cry, laugh, punch the air, hit their partner or fall out of bed, among other actions.

“It may seem comical or curious or related to age, but, in reality, it is the warning sign that, later, when following these patients, they develop Parkinson’s disease and dementia -not Alzheimer’s- of Lewy bodies”, the researcher reiterated.

The percentage of patients with Alzheimer’s in 2010 increased from 45 to 70 per cent, so it was proposed to determine which, utilising a marker, would develop the disease and do so early. As these diseases are characterised by the loss of dopamine in the substantia nigra, Iranzo’s team focused on performing tests such as brain SPECT of the dopamine transporter.

“The usual symptoms of Parkinson’s disease are tremor, rigidity, slowness of movement (bradykinesia) and altered posture, and they appear when 70 per cent of the cells in the substantia nigra are dead. In the second study we did, we found that half of the patients with REM sleep behaviour disorder and no clinical evidence of Parkinson’s showed abnormal brain SPECT of the dopamine transporter, with some deficiency of this substance, and, after three years of follow-up, these patients developed Parkinson’s disease”.

In this way, the REM sleep disorder identifies the preclinical form of Parkinson’s disease, so, for Iranzo, “the ideal would be to give them a neuroprotective drug that, unfortunately, does not yet exist – to prevent them from developing the disease.

The results of this work, carried out on 20 patients with idiopathic REM sleep behaviour disorder, have shown that the amount of dopamine decreases by 20 per cent in three years without having yet developed Parkinson’s disease.

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Tobias Steindl