How Do Sleep Disorders Affect Neurodegenerative Diseases?

Neurodegenerative diseases include a series of ailments in which the neurons of the central nervous system stop working or progressively die. This is the reason why the different neurological signs and symptoms appear.

These types of diseases tend to get worse over time, in addition to having no cure. They can be genetic or caused by a tumor or stroke. In addition, they have a higher incidence in people who ingest large amounts of alcohol or are exposed to certain viruses or toxins.

Sleep disorders can also play a role in neurodegenerative diseases. A study by researchers at the University of Toronto, Canada, reported that REM sleep disorders could be an early warning sign of neurological disease. Let’s go deeper.

How do we dream?

Since the 1960s, scientists have claimed that dreams occur during REM  and that the brain stem is a key region in controlling dreams. This is located at the base of the brain and communicates with the hypothalamus to make the transition from vigilance to sleep and vice versa.

Thus, a chain reaction is initiated by SubC glutamatergic neurons (which regulate the passage from REM to non-REM sleep), which take their name from the area of ​​the brain in which they are found: the nucleus subcoeruleus or SubC. This reaction ultimately produces the release of the neurotransmitter GABA, which, in turn, reduces the level of arousal in the hypothalamus and brain stem.

This neurotransmitter is produced by GABAergic neurons, in charge of controlling the moment of appearance of REM sleep, its effects and, particularly, the muscular paralysis that occurs during deep sleep.

When these cells are activated, they cause a rapid transition to REM sleep. The brainstem sends signals to relax the muscles and not move the limbs.

With this in mind, the researchers set out to thoroughly examine REM sleep disorders, notably cataplexy, narcolepsy, and REM sleep behavior disorder.

REM sleep disorder

People with REM sleep disorder move their limbs or even get up and perform a waking activity while dreaming. In fact, some also talk or yell.

Thus, this disorder is considered a pathology when it endangers the person who sleeps or those around him. Sometimes, the negative consequences of the problem (such as self-harm or damage to the partner during sleep) alert to the diagnosis.

The good news is that REM sleep disorder can usually be treated successfully.

The phases of sleep

What we call “sleep” involves transitions between three different states : wakefulness, REM sleep, and N-REM sleep. There are a variety of characteristics that define each state, but to understand REM sleep behavior disorder it is important to know what happens during it.

During this state, the electrical activity of the brain resembles the electrical activity observed during wakefulness. Although neurons in the brain during REM sleep work in much the same way as they do during wakefulness, REM sleep is nevertheless characterized by temporary muscle paralysis.

In some sleep disorders, such as narcolepsy, parasomnias, or REM sleep behavior disorder, the distinctions between these different states are blurred. The neurological “barriers” that separate these states from each other are believed not to function properly, although the cause of these phenomena is not yet fully understood.

Therefore, most people, even when they are having vivid dreams, are unable to move their body. However, people with REM sleep disorder lack this muscle paralysis, allowing them to enact dramatic or violent dreams during REM sleep.

REM sleep disorders and their relationship with neurodegenerative diseases

By examining the failures in brain circuits that cause these sleep disorders, the researchers made an interesting discovery: REM sleep disorders are linked to several neurodegenerative diseases that tend to occur in old age.

The researchers explain that these findings suggest that neurodegenerative processes initially affect the circuits that control REM sleep and, specifically, SubC neurons.

In addition, they observed that more than 80% of people who suffer from REM sleep disorders eventually develop synucleinopathies, such as Parkinson’s disease and Lewy body dementia.

This research proposes that sleep disorders may be an early warning sign of neurodegenerative diseases  that could appear about 15 years later.

Notably, both Parkinson’s disease and Lewy body dementia are characterized by an intraneuronal accumulation of a protein called alpha-synuclein. That is why the researchers hope that the study of this protein will pave the way for neuroprotective therapies that would prevent the development of neurodegenerative diseases.

In this sense, the researchers argue that, as seen in people prone to cancer, the diagnosis of REM disorders can provide access to preventive actions for the maintenance of neuronal health, long before they develop more serious neurological conditions .