A little-known and poorly understood sleep disorder that occurs during the rapid eye movement, or REM, phase has gained attention for its role in foreshadowing neurodegenerative brain diseases such as Parkinson’s disease and Lewy body dementia. . The disorder, known as REM sleep behavior disorder, or RBD in the medical field, affects around 1% of the general population worldwide and around 2% of adults over the age of 65.
The Conversation spoke with Anelyssa D’Abreu, a neurologist specializing in geriatric neurology, to explain what researchers know about the disease’s links to dementia.
1. What is REM sleep behavior disorder?
Every night you go through four to five cycles of sleep. Each cycle, lasting about 90 to 110 minutes, has four stages. This fourth stage is REM sleep.
REM sleep represents only 20 to 25% of total sleep, but its proportion increases throughout the night. During REM sleep, your brain rhythms are similar to when you are awake, your muscles lose tone, so you are unable to move, and your eyes, when closed, move rapidly. This stage is often accompanied by muscle twitching and fluctuations in your breathing rate and blood pressure.
But someone with REM sleep behavior disorder will achieve their dreams. For reasons poorly understood, the dream content is usually violent – patients report being chased or fighting back, and while sleeping they scream, moan, scream, kick, punch, and thrash about.
Injuries often result from these incidents; patients may fall out of bed or accidentally injure a partner. About 60% of patients and 20% of bed partners of people with this disorder experience an injury while they sleep.
Appropriate tests, including a sleep study, are needed to determine if a patient has REM sleep behavior disorder, as opposed to another disorder, such as obstructive sleep apnea. This is a disorder in which breathing is interrupted during sleep.
REM sleep behavior disorder can occur at any age, but symptoms usually begin in people in their 40s and 50s. For those under 40, antidepressants are the most common cause of REM sleep behavior disorder; in these younger patients it affects biological males and females about equally, but after age 50 it is more common in biological males.
2. What causes REM sleep behavior disorder?
The mechanism of the disease is not well understood. In some cases of REM sleep behavior disorder, a clear cause cannot be identified. In other cases, the disorder may be caused by something specific, such as obstructive sleep apnea, narcolepsy, psychiatric disorders, use of antidepressants, autoimmune disorders, and brain damage, which are areas of damaged brain tissue.
In both situations, REM sleep behavior disorder may be associated with synucleinopathies, a group of neurodegenerative disorders in which aggregates of the protein α-synuclein accumulate in brain cells. The most common of these neurodegenerative diseases is Parkinson’s disease. Others are Lewy body dementia, multiple system atrophy, and pure autonomic failure. REM sleep behavior disorder can precede these illnesses or occur at any time during the disease process.
3. What are the links between sleep disorders and dementia?
REM sleep behavior disorder may be the first symptom of Parkinson’s disease or dementia with Lewy bodies. It is observed in 25% to 58% of patients diagnosed with Parkinson’s disease, 70% to 80% of patients with dementia with Lewy bodies and 90% to 100% of those with multiple system atrophy.
In a long-term study of 1,280 patients with REM sleep behavior disorder who did not have parkinsonism – an umbrella term that refers to brain conditions, including Parkinson’s disease, that cause slowed movements , stiffness and tremors – or dementia, the researchers followed the participants to find out how many would develop these disorders. After 12 years, 73.5% of people with REM sleep behavior disorder had developed a related neurodegenerative disorder.
Some of the factors that independently increased the risk of developing a neurodegenerative disorder were the presence of irregular motor symptoms, abnormal dopamine levels, loss of sense of smell, cognitive impairment, abnormal color vision, erectile dysfunction, constipation and advanced age.
REM sleep behavior disorder can also be seen in other neurodegenerative disorders such as Alzheimer’s disease and Huntington’s disease, but at much lower rates. The association is also less strong than that observed in synucleinopathies.
4. Does early diagnosis help?
For most neurodegenerative disorders, there is a phase that can last for decades during which brain changes occur, but the patient remains asymptomatic or develops symptoms without the full expression of the disease. RBD, in this scenario, is an early sign of these disorders. This provides an opportunity to study disease progression in the brain and develop therapies that could either slow this process down or prevent it from occurring.
Currently, there are no approved treatments to prevent the onset of these neurodegenerative diseases in people with REM sleep behavior disorder. However, there are medications such as melatonin and clonazepam that can improve symptoms. We also recommend measures to avoid injury, such as removing breakable objects from the room, protecting windows and padding floors.
Patients who are affected by REM sleep behavior disorder may choose to participate in research. Proper treatment of the disease can help prevent injury and improve quality of life.