When Dreams Move: understanding REM sleep behaviour disorder in Parkinson's

Introduction

Parkinson's disease does not only affect movement — it can also disturb sleep, and poor sleep can take a toll on both thinking and daily function. That is why recognizing and treating sleep problems matters so much.

Some of the most common sleep disorders in Parkinson's include insomnia, REM sleep behaviour disorder (RBD), excessive daytime sleepiness, sleep apnea, and restless leg syndrome. Knowing exactly which one is present is the first step toward the right treatment and a better quality of life.

One of these disorders shows up in a striking way: a person may move, talk, shout, or even act out a dream — sometimes falling out of bed or getting hurt. These episodes can be a sign of REM sleep behaviour disorder, or RBD.

RBD is common in people with Parkinson's, and it can even appear during the prodromal phase — the early stage before movement symptoms begin. It becomes more frequent the longer a person has lived with the disease, and some studies report it in up to 70% of Parkinson's patients(Sixel-Döring et al., 2023). Remarkably, RBD can also show up years before any movement symptoms ever appear.

In this blog, we will cover what RBD is, what happens in the brain, how it is diagnosed, the available treatments, and simple steps to make nights safer.

What happens during healthy REM sleep

REM (rapid eye movement) sleep is the stage of sleep in which most dreaming occurs.

During healthy REM sleep, a small group of neurons deep in the brainstem — in a region called the subcoeruleus, or sublaterodorsal nucleus (SLD) — sends out a signal that switches off the body's muscles. It does this by activating specialized "inhibitory" neurons in the lower brainstem (the ventromedial medulla) that release two chemical messengers, GABA and glycine. These quiet the motor neurons in the spinal cord that would otherwise move our arms and legs. The result is a natural "pause button" that scientists call muscle atonia: the body stays still and relaxed. At the same time, the mind is busy dreaming(Stefani et al., 2025).

What goes wrong in RBD — and why

In REM sleep behaviour disorder (RBD), this pause button does not work. The brain still produces vivid dreams, but the muscles remain active during REM sleep — a phenomenon sleep specialists call REM sleep without atonia (RSWA)(Stefani et al., 2025). Because the muscles are not switched off, the person physically acts out their dreams: kicking, punching, grabbing, or yelling. Animal and human studies confirm the link, showing that damage to these inhibitory brainstem circuits produces RSWA and dream-enactment (Valencia Garcia et al., 2018).

How to recognize itThere are signs to look for

RBD can look different from one night to the next(Jones & McCarter, 2024). Common signs include:

• Talking, shouting, or laughing while asleep
• Moving, kicking, punching, or grabbing during sleep
• Acting out dreams, often vivid or action-filled ones
• Falling out of bed, or unexplained bruises and cuts in the morning

Often, it is the bed partner who notices first because the person sleeping does not remember the episode. That is why a partner's description can be so helpful at a doctor's visit.

How RBD is diagnosed

Doctors usually start with a few simple questions about your sleep — sometimes a single screening question, sometimes a short checklist. A partner's account is especially valuable here, since the person who slept may not recall the episodes.

To confirm the diagnosis, a doctor may recommend a sleep study called polysomnography. This is an overnight test, usually done in a sleep lab, that records brain activity, muscle movement, breathing, and heart rate while you sleep. It is the most reliable way to tell RBD apart from other sleep conditions. Knowing what is really happening helps your care team recommend the right next steps(Cesari et al., 2025).

Treatment: what can be done about it?

Here is the reassuring part: there is no cure for RBD yet, but it can be managed well, and there are practical things that help. The main goal is to prevent injuries during sleep. In fact, when symptoms are mild and are not causing harm, some people and their doctors decide that no medicine is needed at all. Your doctor will guide you on what is right for you, but most plans start with making the bedroom safer(Roguski et al., 2020).

Good sleep habits — a regular bedtime and a calm, healthy routine — are also encouraged as part of any plan.

When medicines are considered

If safety changes are not enough, your doctor may add a medicine. The two most common options are melatonin, which tends to cause fewer side effects, and clonazepam, a long-used medicine that calms the overactive brain signals behind RBD. Both can reduce how often dreams are acted out. Every situation is different, so which medicine (if any) is chosen is always decided together with your care team(Roguski et al., 2020).