The concept of sleep is hard to wrap your head around at the best of times, let alone when you start to explore all the weird and terrifying things that can happen to us during the night.

REM sleep behaviour disorder is a prime example. This form of parasomnia – a catch-all term for the unusual behaviours that people experience prior to falling asleep, during sleep and as they wake up – may be rare, but the disruption it can cause makes it stand out.

In the simplest terms, it causes people to act out their dreams; the reasons and the risk factors that can lead to it, however, are a lot more complicated.  

As you might expect from the name, REM sleep behaviour disorder is a condition that occurs during the rapid eye movement stage of sleep. You might already know that this is the stage of sleep associated with dreaming – a time during which we typically lose muscle control.

This phenomenon is known as atonia. “Atonia is something that usually happens when you enter REM sleep,” Theresa Schnorbach, Emma’s sleep expert, explains. “This helps to protect you from injury by placing your body in a sort of paralysis to stop you from acting out your dreams.”

In people with REM sleep behaviour disorder, this paralysis doesn’t occur, leading them to physically act out and respond to their dreams. It’s distinct from other sleep conditions such as sleepwalking, sleep-related epilepsy or sleep terrors, but can look similar due to the movement that occurs. 

Because REM sleep behaviour disorder occurs in the absence of atonia, it leads the person affected to move and act out in response to their dreams, both physically and vocally.

“REM sleep behaviour disorder is often characterised by movement of the limbs and violent activity (such as punching or kicking) as well as vocal sounds (such as shouting or talking),” Schnorbach explains. “Episodes typically occur around 90 minutes after sleep as this is when the body tends to enter into the REM sleep stage.” 

If you’ve never heard of REM sleep behaviour disorder before, that’s because it’s relatively rare. The condition affects around 1% of the population; men over the age of 60 are at the highest risk, but there are other risk factors associated with the condition too.

These include neurological disorders including cerebral vascular disease, brain tumours and dementia, as well as the sleep disorder narcolepsy. Withdrawal from substances including alcohol and hypnotics, has also been known to induce the disorder, as have certain medications – including some antidepressants.

SSRIs, in particular, have been linked to an increased risk of REM sleep behaviour disorder due to the possible link the condition has to the serotonergic system – the system which manages serotonin in the body.

However, it’s important to remember that the risk of developing REM sleep behaviour disorder is still small while on these medications, and more research is needed to find out how big a link the two share.  

There are several different ways to deal with REM sleep behaviour disorder, many of which are aimed at minimising the risk of harm both to the sufferer and their partner where applicable.

Physically, that might mean clearing sharp and breakable objects from the area around the bed, as well as identifying and eliminating triggers such as drugs and alcohol.

In some cases, Schnorbach adds, medication can be used to manage the condition; melatonin in particular has been found to help, but only when prescribed in the correct dosage by a sleep doctor.

If you’re concerned that you or a loved one may be dealing with REM sleep behaviour disorder, you should seek the advice of a doctor or sleep expert before introducing any interventions. 

Images: Getty