When a person suddenly swings a fist, kicks and shouts in the middle of the night during sleep, or even falls out of bed or hurts the person beside them, the first reaction of many people is to assume it was just an unusually vivid nightmare. In some people, however, this night-time dream enactment is a prodromal sign of brain degeneration that medicine takes very seriously: REM sleep behaviour disorder (RBD). This page is an in-depth version of the overview of non-motor early signs of Parkinson's disease, and concentrates on RBD as an early warning. It covers how RBD differs from ordinary dreaming and sleepwalking, why it has become a warning that appears 10 to 20 years early for Parkinson's disease or dementia with Lewy bodies, the real statistics on conversion risk, when to see a doctor for a sleep study, and the most practical part, which is how to set up a safe sleeping environment.
First, clarifying roles: The diagnosis and treatment of RBD belong to neurologists or sleep specialists, and cannot be decided by self-testing or reading information online. Nova Health is a home rehabilitation and nursing team. Our work is to help improve the safety of the bedroom environment (preventing falls out of bed or injury to the bed partner) and to help patients keep up their physical function once Parkinson's disease has been diagnosed. We do not make medical diagnoses. The content of this page is meant to help readers understand when to see a doctor, and cannot replace a doctor's professional advice.
What does punching and kicking in sleep mean? Understanding RBD
When a normal person enters REM (rapid eye movement) sleep, the stage when dreaming is most frequent, the body automatically switches on a muscle relaxation (atonia) mechanism, as if the limbs were temporarily locked, so that even if the dream is intense, the body does not really move. The core problem in RBD is that this relaxation mechanism fails. Because the muscles are not locked, the patient acts out the content of the dream in person: swinging fists when dreaming of a fight and kicking out when dreaming of running away, often with shouting or sleep talking, and with movements violent enough to throw the person out of bed or hurt the bed partner by mistake.
RBD is not a rare disease, but it is not a common phenomenon either. The estimated prevalence in the general population is about 0.5%. It usually begins between the ages of 60 and 70, and is more common in older men (StatPearls 2024). What medicine pays attention to is not how alarming the punching and kicking looks, but that this kind of dream enactment often reflects a particular process of neurodegeneration in the brain.
How RBD differs from ordinary dreaming and sleepwalking
Restless sleep or twitching of the hands and feet in the night is not the same as having RBD. To tell them apart accurately, look at three things: whether the body is supposed to be able to move, what time of night it happens, and whether the person remembers anything on waking:
- Happens in REM sleep. The muscles should be relaxed but are not, so the dream is acted out
- Mostly in the second half of the night (when REM is more frequent)
- Movements match the dream: swinging fists, kicking and shouting, and the person may fall out of bed or hurt the bed partner
- The person can be woken, and can usually describe the dream on waking
- Normal dreaming: the muscles are relaxed as if locked, and however intense the dream, the arms and legs do not really move
- Sleepwalking is mostly in deep (non-REM) sleep in the first half of the night
- In sleepwalking the person can get up and walk, but the movements are more mechanical and do not necessarily match a dream
- A sleepwalker cannot be woken, and usually remembers nothing on waking
Occasional nightmares, sleep talking or twitching of the legs during sleep are in the great majority of cases unrelated to RBD, and there is no need to worry too much. What really calls for medical follow-up is dream enactment that is persistent, repeated, involves violent movements, and has already injured the person or the bed partner. The final diagnosis must be decided by a doctor (with a sleep study if needed), and a diagnosis should not be made from an article alone.
The link between RBD and Parkinson's disease and dementia with Lewy bodies
Parkinson's disease, dementia with Lewy bodies (DLB) and multiple system atrophy (MSA) all belong to the group of neurodegenerative diseases called alpha-synucleinopathies (synucleinopathy), and in all of them the pathology involves the build-up of an abnormal protein called alpha-synuclein inside nerve cells. The brainstem nuclei that control muscle relaxation in REM sleep are often among the first areas affected in the whole process of degeneration. In other words, when the mechanism that locks the muscles fails and dream enactment appears, it may reflect that degeneration has quietly started in the brainstem. The substantia nigra, which controls motor function, often does not become badly damaged until many years later, and only then do the typical symptoms of tremor, slowness and stiffness appear.
By the time the hand begins to tremble, degeneration in the brain has already gone a fair way. RBD is one of the most specific and most noteworthy clues from this period before the tremor appears.
Research data on iRBD converting to Parkinson's disease or dementia
RBD for which no other obvious cause can be found is called idiopathic / isolated RBD (iRBD) in medicine. Several large prospective studies in recent years have confirmed its conversion risk again and again. The data consistently show that the proportion who convert is high, but they also show that the process takes a long time and differs from person to person.
How should readers interpret these figures? First, the longer the person has had the condition, the higher the proportion who convert, which means RBD is not a one-off risk but a state that needs long-term follow-up and monitoring. Second, an individual's risk is influenced by several factors. Another multicentre study (Postuma 2015) confirmed that older age, a family history of Alzheimer's disease, mild motor signs (such as a stooped posture or slight tremor) or autonomic dysfunction are all predictors of conversion. Third, and most important, the figures above are only group statistics and in no way mean that every case will eventually develop the disease, and the studies also include people who were followed for many years without converting.
A common myth: does poor sleep mean Parkinson's disease?
Absolutely not. The points below must be made clear, so that readers do not come away with needless anxiety:
- Occasional nightmares, sleep talking, twitching of the legs or a poor night's sleep are in the great majority of cases unrelated to RBD and Parkinson's disease, and there is no need to panic.
- The "high conversion proportion" mentioned in the research literature refers to patients whose iRBD has been confirmed by a sleep study. Without a confirmed diagnosis from testing, a person should not assume they have iRBD and apply these risk figures just because they move in their sleep.
- Acting out dreams during sleep can also be caused by sleep apnoea, by other treatments the person is receiving, or by other causes. These may not be degenerative RBD and need to be told apart by a doctor.
- Only dream enactment that is persistent, repeated, violent, or has already injured the person or the bed partner needs assessment by a doctor. Not everyone who sleeps badly has a problem.
Medical controversy and uncertainty: Even when iRBD has been diagnosed, medicine currently has no proven method of stopping or reversingits later development into other degenerative diseases, and related research is still going on. The point of the diagnosis is therefore to know that regular monitoring is needed and that sleep safety measures should be put in place early, and not to change the course of the disease at once. Regarding RBD as certain to lead to Parkinson's disease, or ignoring it completely, is not in line with the facts.
Local research in Hong Kong: family genetic risk and public awareness
This medical topic has weighty local research behind it in Hong Kong. In 2019, the Faculty of Medicine of The Chinese University of Hong Kong (the research team of 榮潤國, 莫仲棠, 林少萍 and 張繼輝) published the world's first family study of RBD in Annals of Neurology. It found that first-degree relatives of RBD patients had a risk of Parkinson's disease and neurodegenerative disease 3 to 6 times higher than that of ordinary families. The team also noted that about 90% of RBD patients develop Parkinson's disease or other signs of neurodegeneration after 5 to 15 years, and that following early signs such as constipation could allow intervention about 20 years earlier. (Note: this passage quotes the 2019 press release of the CUHK Faculty of Medicine, and the original study was published in Annals of Neurology.)
Public awareness of the signs is clearly lacking as well. A survey carried out in 2023 by the School of Nursing of The University of Hong Kong showed that nearly 70% of Hong Kong people overlook the four non-motor early signs of Parkinson's disease (punching and kicking while dreaming, constipation, depression and loss of the sense of smell), and only about 17%know that dream enactment is linked to Parkinson's disease. Local media have also estimated that there are more than 12,000 people with Parkinson's disease in Hong Kong, and that about 1 in 30 older adults over 70 has the disease. This gap, in which almost everyone has seen the early signs but few know what they mean, is exactly the one this page hopes to fill. The purpose of learning about RBD is not to cause panic, but to let families know when to act.
When to see a doctor and have a sleep study
A single occasional nightmare is of course no reason for urgent consultation. If the following occur, however, serious consideration should be given to being referred through a family doctor to a neurologist or sleep specialist for a detailed assessment:
- The person often swings fists, kicks or shouts during sleep, and these movements match the content of the dream at the time.
- The person has fallen out of bed, hurt themselves, or hit the bed partner because of violent movements during sleep.
- The bed partner sees the person acting out dreams during sleep, and the person usually also remembers clearly on waking what was dreamt.
- Besides dream enactment, other early signs of Parkinson's disease occur at the same time, such as long-term constipation, reduced sense of smell, persistently low mood, slight hand tremor or slower movement.
- A family member has had Parkinson's disease or neurodegenerative disease, and the person also has the situations above.
Poor sleep quality is not always just ordinary insomnia. Violent movements during sleep need to be assessed by a doctor to find the cause, and should not be dealt with on your own. When seeking help, the person can first see a family doctor and explain the situation clearly, and the doctor can then refer the person to a neurologist or sleep specialist for follow-up.
How RBD is diagnosed: polysomnography (video-PSG)
The gold standard for diagnosing RBD is a polysomnography (video-PSG) study in a sleep laboratory, which records brain waves, eye movements and muscle tone at the same time, with video recording throughout. Under the diagnostic criteria of the International Classification of Sleep Disorders (ICSD-3), the key to the diagnosis is observing REM sleep without atonia (RWA), together with dream enactment, and ruling out other sleep disorders such as sleep apnoea that could explain the symptoms (StatPearls 2024).
- 1See the family doctorTell the doctor in detail how often movements occur at night, how severe they are, whether the person has ever been injured, and whether there are other early signs and a family history.
- 2Referral to neurology / sleep medicineA specialist carries out a clinical assessment and decides whether further tests are needed.
- 3Polysomnography (video-PSG)The person sleeps one night in the sleep laboratory, during which brain waves, eye movements and muscle tone are recorded together and the whole night is recorded on video. This can confirm whether the patient lacks normal muscle relaxation in REM sleep (RWA), and rule out other sleep problems.
- 4Long-term monitoring after diagnosisA neurologist follows up regularly and monitors for early signs of Parkinson's disease or dementia, and deals with symptoms and arranges rehabilitation training as needed.
In Hong Kong, the video-PSG study is carried out mainly in the sleep laboratories of public hospitals or in private sleep centres. Besides confirming whether it is RBD, the test can also rule out other sleep problems that can be treated. So even if the final result is not RBD, doing the test still serves a purpose.
How to set up a safe sleeping environment to prevent injury
Whatever the final diagnosis, making the sleeping environment safe is the most practical step and can be started at once. International guidelines (AASM 2023) also list maintaining a safe sleeping environment to prevent injury at night as a core focus in managing RBD. While waiting for a consultation, family members can first take the protective measures below:
| Remove dangerous objects | First put away sharp objects, hard objects and items that could injure someone from beside the bed. Cover the sharp corners of the bedside table with soft padding, and move furniture away so that it is not placed too close to the bed. |
| Cushion falls | Lay a soft mat or mattress on the floor beside the bed. A low bed can also be considered, or the mattress can be put straight on the floor, so that the impact is reduced if the person falls out of bed. |
| Protect the bed partner | If the movements are too violent or the person often hits the person beside them, the couple can consider sleeping apart for the time being, or put a pillow between them or add a bed rail at the side as a buffer. |
| Secure the exits | Lock the bedroom windows and doors before sleep, so that the patient does not accidentally move to a dangerous place during large movements in the night. |
It must be made clear: the measures above are only protective measures to prevent injury, and they cannot replace a doctor's diagnosis and treatment. The home visit team at Nova Health can help to assess the safety of the bedroom environment and give advice on modifications, but the diagnosis and treatment of the disease always remain the responsibility of the doctor.
Overview of the medical management of RBD
The key medical reality must be stated first: at present no method has been proved to stop or reverse the later development of RBD into Parkinson's disease. The treatment goal in medicine at present is mainly to control symptoms and reduce violent movements and the risk of injury at night, and not to change the course of the disease. In the clinical practice guideline published by the American Academy of Sleep Medicine in 2023 (Howell 2023), all the recommendations for adults with isolated RBD are of conditional grade, which means the strength of the existing evidence is limited and the doctor must weigh benefits and risks for each patient.
Put simply, there is as yet no standard treatment plan that suits everyone. The more practical approach at this stage is to leave medical issues to the doctor, make bedroom safety measures at home, and have a neurologist follow up regularly, so that any early signs of Parkinson's disease are dealt with as soon as they appear.
Support services provided by Nova Health
In the end, the diagnosis and treatment of RBD belong to the professional field of doctors. Nova Health provides home physiotherapy and nursing services, and what we can support alongside the medical diagnosis are the equally practical parts: