What Is Sleep Rhythmic Movement Disorder?

If you’ve ever peeked in on your baby in their crib and spotted them rocking back and forth, you might have felt—rightfully—concerned. Or maybe your bed partner has been periodically rolling their head from side to side at night, and you’re wondering, What’s up with that?

The good news is, these movements aren’t a sign that something is wrong, and in children, they’re a normal part of development. They also have a name: sleep rhythmic movement disorder (RMD).

Still, if your child is hurting themselves with their movements, or your bed partner has been threatening to kick you into the guest room because apparently you swing your head violently and keep them awake, it might be a good idea to talk with a healthcare provider. 

Ahead, we dive into everything you need to know about RMD, including the signs, who can have it, and how to keep you or your child safe while sleeping.

What is sleep rhythmic movement disorder (RMD)?

RMD involves repetitive, rhythmic movements of the large muscles of the body. While it most commonly happens right as you fall asleep, or during light sleep, RMD can happen in all sleep stages, including rapid eye movement (REM) sleep—the stage of sleep where dreaming occurs. This means RMD can really happen at any point while sleeping.

The movements from RMD look different from other forms of movement like tremors, seizures, or jerking. RMD movements themselves aren’t always a problem, unless they cause injury or interfere with getting good sleep. 

Common types of rhythmic movements

The rhythmic movements of RMD show up mainly in your head, neck, and trunk. These movements can look like ^[1]:

• Body rocking: Rocking the whole body back and forth
• Body rolling: Rolling the entire body from side to side
• Head banging: Repeatedly knocking the head on a pillow, wall, crib slats, or mattress 
• Head rolling: Rolling your head repeatedly from side to side

Head-rolling is the most common symptom of RMD, and some people will do more than one type of movement. Some children also might make rhythmic noises like humming.

RMD in infants and children vs. adults

RMD happens mostly in infants and children. Research shows that about two in every three 9-month-olds have RMD. At 18 months, only about one in three children shows these rhythmic movements around sleep. By age 5, those numbers drop to less than one in 10. 

In older children, teens, and adults, RMD is much rarer. So much that there have been no studies done on how common RMD is in adults. While healthcare providers don’t tend to treat RMD in children, adults might require an evaluation since the condition can occur with other health conditions.

What causes RMD?

Researchers aren’t sure of the exact cause of RMD. In infants and toddlers, these repetitive movements may act as a self-soothing behavior that helps children settle to sleep. Babies often rock or shake their heads while falling asleep or while sleeping. This is normal behavior and shows up around the same time they’re learning new skills like sitting, crawling, or standing.

Interestingly, almost 60 years before researchers recognized RMD as a sleep condition, it was portrayed in the Disney film Snow White and the Seven Dwarfs. One of the dwarfs, Dopey, lies down to sleep and has rhythmic movements of his head as well as soft vocalizations. When he’s touched, Dopey opens his eyes. The movements stop, and he sighs and goes back to sleep.

When RMD continues past early childhood, it’s sometimes seen alongside other conditions such as autism, Down syndrome, and attention-deficit/hyperactivity disorder (ADHD). People who have RMD can also have other sleep disorders, including insomnia, restless legs syndrome, sleep apnea, and night terrors.

RMD may be genetic because the disorder has appeared in families. Studies have found the condition in twins and triplets, but more research is needed to understand the genetic link.

How is RMD diagnosed?

In many children, RMD can be diagnosed based on a detailed description from the parents. It’s helpful to bring in a home video of the movements.

But just because your child might have rhythmic movements, it doesn’t necessarily mean they will be diagnosed with RMD. According to the International Classification of Sleep Disorders (third edition), you need to meet the following criteria to receive an RMD diagnosis:

• Repetitive, rhythmic movements in the large muscles
• Movements mainly happen during sleep times
• Movements interfere with sleep quality or cause injury
• Movements can’t be explained by another health condition such as a seizure disorder

When RMD affects adults, healthcare providers might order an overnight sleep study, known as a polysomnography, combined with video monitoring. This is to help detect an accompanying sleep disorder such as obstructive sleep apnea (OSA) or periodic limb movement disorder (PLMD). 

Some health conditions can mimic some movements seen in RMD. This can include:

• Seizures: Some seizures that happen during sleep show brief movements, but during an electroencephalogram (EEG), there are no changes in brain waves with RMD.
• Restless legs syndrome (RLS): RLS causes an uncomfortable urge to move the legs,  and often happens in the evening while a person is awake. But people with RMD are often asleep or drowsy and don’t have a trigger that causes movements.
• Sleep tremors: Some sleep-related movements cause small, quick, involuntary tremors, while RMD movements are larger, slower, and involve the large muscle groups. 

Treating RMD

Most children and adults with RMD don’t need any treatment at all. Managing the condition revolves around keeping you or your child safe while sleeping.

Some safety adjustments you can make to your or your child’s sleeping space include:

• Padding bed rails
• Moving the mattress to the floor
• Moving the bed away from the wall
• Placing padding (such as pillows and blankets) on the floor
• Removing sharp headboard edges

Since RMD can occur with other sleep disorders such as obstructive sleep apnea (OSA) or periodic limb movement disorder (PLMD), treating those conditions, such as using a CPAP (continuous positive airway pressure) machine, can help decrease RMD symptoms.

For adults, healthcare providers might prescribe medications such as clonazepam, which can reduce symptoms like head banging to protect from injury.

FAQ

Is rhythmic movement during sleep normal in babies and toddlers?

Yes, rhythmic movements like head rolling and body rocking are common in infants, with research showing that more than half of 9-month-olds do them. Most children outgrow them, and the behavior is generally considered harmless.

When does sleep rhythmic movement disorder require medical evaluation?

See a healthcare provider if the movements cause injury, disrupt sleep, or cause you to be tired during the day. If these movements start in later childhood or adulthood, it’s also a good idea to be evaluated and to rule out other sleep conditions.

How is sleep rhythmic movement disorder different from seizures?

RMD movements are rhythmic and slower than the movements that happen with seizures. RMD tends to happen right before someone falls asleep, whereas abnormal electrical activity causes seizures in the brain.

References:

1. Lam, N., & Veeravigrom, M. (2023). Sleep-related rhythmic movement disorder in children: A mini-review. Frontiers in Neurology, 14, 1165130. https://doi.org/10.3389/fneur.2023.1165130. https://pmc.ncbi.nlm.nih.gov/articles/PMC10225739/
2. Michalek-Zrabkowska, M., Wieckiewicz, M., Wichniak, A., Jenca, A., Jr, Jencova, J., Frosztega, W., Wieczorek, T., Chojdak-Lukasiewicz, J., Sluzewska-Niedzwiedz, M., Wojakowska, A., Poreba, R., Mazur, G., & Martynowicz, H. (2024). Sleep-related rhythmic movement disorder in adults – A systematic review with a case report. Journal of sleep research, 33(1), e13985. https://doi.org/10.1111/jsr.13985. https://pubmed.ncbi.nlm.nih.gov/37414586/
3. Janković, S. M., Sokić, D. V., Vojvodić, N. M., Ristić, A. J., & Kostić, V. S. (2009). The first cinematic presentation of a possible rhythmic movement disorder in a Disney film precedes its scientific debut by 60 years. Movement Disorders, 24(1), 143-144. https://doi.org/10.1002/mds.22232. https://movementdisorders.onlinelibrary.wiley.com/doi/10.1002/mds.22232
4. Al Sa’idi, L., Gupta, A., & Shukla, G. (2024). Sleep Related Rhythmic Movement Disorder in older children and adults and their association with comorbid conditions – experience from two centres and literature review. Sleep Medicine, 113, 299-305. https://doi.org/10.1016/j.sleep.2023.11.037. https://www.sciencedirect.com/science/article/abs/pii/S138994572300463X
5. Manni, R., & Tartara, A. (1997). Clonazepam Treatment of Rhythmic Movement Disorders. Sleep, 20(9), 812. https://doi.org/10.1093/sleep/20.9.812. https://academic.oup.com/sleep/article-abstract/20/9/812/2731702