A little-understood sleep disorder affects millions of people and has a clear link to dementia – 4 questions answered

A little known and poorly understood sleep disorder that occurs during the rapid eye movement, or REM sleep phase, has attracted attention for its role in foreshadowing neurodegenerative brain diseases such as Parkinson’s disease and dementia with Lewy bodies. The disorder, known as REM sleep behavior disorder, or RBD in the medical field, affects about 1% of the general population worldwide and about 2% of adults over the age of 65.

The Conversation spoke with Anelyssa D’Abreu, a neurologist who specializes in geriatric neurology, to explain what researchers know about the link between the condition and dementia.

1. What is REM Sleep Behavior Disorder?

Every night you go through four to five sleep cycles. Each cycle, which lasts about 90 to 110 minutes, has four phases. The fourth stage is REM sleep.

REM sleep comprises 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’re awake, your muscles lose tone so you can’t move, and your eyes, while closed, move quickly. This phase is often accompanied by muscle twitching and fluctuations in your breathing rate and blood pressure.

But someone with REM sleep behavior disorder will make their dreams come true. For reasons that are poorly understood, the dream content is usually violent – ​​patients report being chased or defending themselves, and screaming, moaning, screaming, kicking, punching and thrashing around while asleep.

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 condition are injured during 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 condition where breathing is interrupted during sleep.

REM sleep behavior disorder can occur at any age, but symptoms usually begin in people between the ages of 40 and 50. For those under age 40, antidepressants are the most common cause of REM sleep behavior disorder; in these younger patients it affects approximately equal numbers of biological males and females, but after age 50 it is more common in biological males.

See a sleep specialist or neurologist if you suspect you have REM sleep behavior disorder.

2. What Causes REM Sleep Behavior Disorder?

The disease mechanism is not well understood. In some cases of REM sleep behavior disorder, no clear cause can be identified. In other cases, the disorder may be caused by something specific, such as obstructive sleep apnea, narcolepsy, psychiatric disorders, antidepressant use, autoimmune disorders, and brain lesions, 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 disorders is Parkinson’s disease. Others are dementia with Lewy bodies, multiple system atrophy and pure autonomic failure. REM sleep behavior disorder can precede these illnesses or occur at any point during the disease process.

People with REM sleep behavior disorder can harm themselves and their bed partners.

3. What are the links between the sleep disorder 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, in 70% to 80% of patients with Lewy body dementia, and in 90% to 100% of patients 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 disorders, including Parkinson’s disease, that cause slowed movements, stiffness and tremors — or dementia, researchers followed participants to discover how much these disorders would develop. After 12 years, 73.5% of those with REM sleep behavior disorder had developed a related neurodegenerative disorder.

Some of the factors that independently increased the risk of developing neurodegenerative disease included the presence of irregular motor symptoms, abnormal dopamine levels, loss of sense of smell, cognitive impairment, abnormal color vision, erectile dysfunction, constipation, and older age.

REM sleep behavior disorder can also be seen in other neurodegenerative disorders such as Alzheimer’s disease and Huntington’s disease, but to a much lower degree. The association is also not as strong as that observed in the synucleinopathies.

4. Does early diagnosis help?

For most neurodegenerative disorders, there is a phase that can last for decades in which brain changes occur, but the patient either remains asymptomatic or develops symptoms without full manifestation of the disease. RBD is an early sign of those conditions in that scenario. This offers the opportunity to study how the disease progresses in the brain and to develop therapies that can slow down or prevent this process.

At this time, there are no approved therapies 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 prevent injury, such as removing breakables from the room, protecting windows, and filling floors.

Patients suffering from REM sleep behavior disorder may choose to participate in research. Proper treatment of the disease can help prevent injury and improve quality of life.

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