An Innsbruck research team has developed a diagnostic tool using artificial intelligence (AI) to detect and manage isolated REM sleep behavior disorder (iRBD), which can be a harbinger of Parkinson’s and other diseases of the nervous system. 

The study is published in the European Journal of Neurology

Kicking, screaming, lashing out—the sleep disorders can turn the night into a nightmare. These nocturnal outbursts are usually caused by iRBD. Birgit Högl, MD, a neurologist and head of the Sleep Disorders Unit at the Medical University of Innsbruck, estimates that one in 100 people has iRBD, which affects men and women equally and is more frequently diagnosed in older people. 

That being said, exact numbers are hard to come by as those with the condition are often not aware, and patients who present with the corresponding symptoms usually need to wait for a long time to be examined.

People who have the sleep disorder are not themselves while they are asleep or dreaming. “For instance, they will be aggressive or dangerous. Anyone sharing their bed may end up with a busted lip or a black eye. And they are also prone to hurting themselves, for instance when they fall out of bed,” says Högl in a release.

In collaboration with Heinrich Garn and Bernhard Kohn of the Austrian Institute of Technology, Högl and her team equipped a high-tech camera with artificial intelligence capabilities to detect iRBD-specific movements. 

“The method has turned out to be so exact that it is fit for use in the hospital,” says Matteo Cesari, MSc, PhD, a bioengineer and the lead author of a current study that is part of the project, in a release. 

The Austrian Science Fund financed the project, which has by now turned into an EU project in which researchers are further developing the technology to make it suitable for mass screenings. iRBD presents a risk not only to the people affected and those sleeping close to them, but it is also the most sensitive and specific marker for dying nerve cells. To slow down this neurodegenerative process, it is key to diagnose it as early as possible.

Muscle Paralysis During REM Sleep

A sleep disorder is easy to detect when the person concerned has trouble sleeping. For disorders such as iRBD, a diagnosis is much more difficult to come by. If a person has iRBD, their muscles are not paralyzed during the REM stage the way they are in healthy people. 

“The legs and arms of iRBD patients tend to twitch rapidly. They also move in a way that looks like they are acting out their dreams lying down,” Högl says in the release.

The sleep expert thinks that it is due to social reasons that iRBD is more often diagnosed in men. While many women are single and sleep alone at later stages of their life, older men share their bed more often, so that the disorder is more easily found. In general, however, it often goes undetected. 

“Some people don’t even know that it is not normal to actually carry out all the movements you are dreaming about in your sleep,” Högl says in the release. 

iRBD as a Sure Sign of Neurodegeneration

A person older than 50 who suddenly starts to move or behave strangely (with or without dreams) during their sleep is advised to consult a sleep lab. Physicians can prescribe medication that can ease the symptoms of iRBD, but the disorder is a clear indication of the loss of nerve cells and is thus often associated with other diseases. 

“Ninety percent of all patients with iRBD develop a neurodegenerative disease such as Parkinson’s, Lewy body dementia, or multiple system atrophy.”

Birgit Högl, MD, neurologist and head of the Sleep Disorders Unit at the Medical University of Innsbruck

“Ninety percent of all patients with iRBD develop a neurodegenerative disease such as Parkinson’s, Lewy body dementia, or multiple system atrophy,” Högl says in the release. Often, this happens over the course of several years.

This is why iRBD patients are an ideal target group for newly developed drugs that can help slow down the degenerative process. At the moment, a lot of research is carried out in this field. If it’s known a patient has the disorder, many of their nerve cells have already died. “An iRBD diagnosis can give us a 10-year head start. But the sleep lab is currently the needle’s ear,” Högl says in the release.  

Long Wait Times to be Diagnosed

For the moment, sleep disorders can only be reliably diagnosed in sleep labs. Data from polysomnography are collected and manually assigned to the various sleep stages. As this requires a lot of staff and time, patients have to wait for a year or longer to get an appointment in a sleep lab in Austria. 

Högl’s research group has addressed this shortcoming by creating an automated solution for diagnosing iRBD. Their goal was to come up with a tool that could also be used to screen healthy people in order to detect the risk of developing a neurodegenerative disease early on.

“The time-of-flight camera we use for our method is also used as a Kinect sensor in the Xbox console,” Cesari says in the release. The 3D camera emits infrared radiation, which is reflected by the sleeping person’s body. By measuring the reflected signals, the distance between the camera and the person can be calculated. “We take 30 pictures a second and get the distance for every pixel. If the distance changes, we know that the person has moved in their sleep,” he adds.

Predictions With an Accuracy Rate of 87%

To analyze the camera data, the researchers developed an AI-based solution to minimize manual steps as far as possible. In their study, Cesari and his colleagues presented the newest version of the system, which merges analysis data of several body parts using a machine learning mechanism. 

“We collate the movements of the person’s legs, torso, hands, and head during REM sleep. Superimposing the data onto each other this way gets us the best results,” Cesari says in the release. The system’s detection rate for iRBD patients is 87%, which is close to the more resource-intensive, multi-factor examination in the sleep lab. 

As a next step, the system will be fine-tuned with the help of an EU-wide cooperation.

Team from Innsbruck Coordinates EU Project

To diagnose iRBD, the system needs to identify the movement data from the REM stage. For now, this step still requires additional measurements. “We are currently working on turning it into a stand-alone method. To this end, we are coordinating a study with 300 test subjects,” Cesari says in the release. 

Sleep labs from Germany, Italy, Spain, and France will participate. The team is also trying to downscale the hardware from currently 2 kilograms to 13 grams to turn it into a mobile device.

The team’s vision is to develop what they describe as “an automated sleep lab fit for home use,” which could be used for comprehensive screenings across the population. “A person developing iRBD requires a solid diagnosis, consultation, and check-ups,” Högl says in the release. “They should understand their condition and know that it is possible to delay the progress of a neurodegenerative disease.”

Photo caption: To replace the personnel- and time-intensive examinations in the sleep laboratory, a team from Innsbruck developed an AI-based approach that detects REM sleep behavior disorders. 

Photo credit: Medical University of Innsbruck.