Narcolepsy is a neurological sleep disorder that affects approximately 1 in every 2,000 people. Narcolepsy is characterized by disturbances in sleep cycles and rapid eye movement (REM) sleep. Hallmark sleep-related symptoms of narcolepsy include:
All of these symptoms make life with narcolepsy difficult. This article discusses disturbances associated with sleep-wake cycles and REM sleep patterns that contribute to these symptoms.
Evidence shows that nerve cells responsive to the hormone hypocretin (also known as orexin) in an area of the brain called the hypothalamus act as the switch between states of sleep and wakefulness.
In people with narcolepsy, this switch doesn’t appear to work well. This is because hypocretin is dysregulated in people with narcolepsy. The degree of hypocretin depletion often depends on the type of narcolepsy that a person has. People with type 1 narcolepsy (also known as narcolepsy with cataplexy) tend to have less hypocretin. Type 1 narcolepsy is associated with more severe symptoms than type 2.
In a sleep study conducted in people with narcolepsy, those who had low hypocretin levels had more transitions between sleep and wakefulness as well as to and from REM sleep. People with narcolepsy type 1 also had more sleep-wake transitions compared to those with narcolepsy type 2. Research has also shown that people with narcolepsy type 1 have more transitional periods between wakefulness and REM sleep and between wakefulness and non-REM sleep. Sleep studies and polysomnographic recordings suggest that the number of sleep cycles a person experiences in a given night might also be a useful diagnostic tool for type 1 narcolepsy.
In another study, people with narcolepsy type 2 also had more sleep state transitions compared to non-narcoleptic controls who experience normal sleep. This study also linked abnormal sleep cycle transitions in both types of narcolepsy to the HLA-DBQ1 gene, which has a known role in the development of narcolepsy.
Overall, these unstable distributions of sleep states and abrupt cycle transitions are hallmark features of narcolepsy. They’re also a major contributing factor in excessive daytime sleepiness. These disruptions in sleep architecture may also contribute to other negative symptoms associated with narcolepsy, such as depression.
REM sleep is the period of sleep in which dreaming happens. As mentioned above, people with narcolepsy transition in and out of REM sleep more often than those without narcolepsy. In fact, REM sleep behavior disorder has been thought of as an intrinsic component of narcolepsy. Although disruptions in REM sleep appear to be linked to hypocretin deficiency, they are not limited to type 1. People with a type 2 diagnosis also have disrupted REM sleep cycles.
Disruptions in transitions to and from REM sleep are related to why people with narcolepsy fall asleep suddenly and without warning. Typically, during these sudden bouts of sleep, individuals with narcolepsy fall directly into REM sleep, unlike healthy counterparts who first experience a cycle of non-REM sleep, including light sleep and deep sleep.
Sleep paralysis is also associated with REM sleep. Two unique features of REM sleep are that REM is when you typically do your dreaming. Also, your body is usually paralyzed during REM to stop you from acting out your dreams. This relationship explains why people with narcolepsy experience sleep paralysis immediately upon waking or right before falling asleep — their brains are still in REM sleep, so they can’t move. Further, falling in and out of REM sleep may be why people with narcolepsy experience hallucinations at times of waking or sleep onset. This is because their brains are actually in a dreaming state. In both cases (sleep paralysis and hallucinations), the individual is just either coming out of or entering an REM sleep episode.
Cataplexy can also be explained by the relationship between narcolepsy and REM sleep. During cataplexy, individuals experience muscle paralysis. As noted above, in REM sleep, the body is paralyzed so that you don’t act out what’s happening in your dreams. When this occurs when someone is awake, they have the sudden muscle weakness of cataplexy.
The multiple sleep latency test (MSLT) is one diagnostic tool that examines how readily people who potentially have narcolepsy fall in and out of REM sleep during the daytime. In order to diagnose narcolepsy on MSLT, REM sleep (which is usually not seen on brief naps) is experienced during the short nap tests.
Overall, understanding that these disruptions in sleep cycles and REM sleep are a normal component of narcolepsy can provide insight into the diagnosis of this disease, as well as helping individuals understand their disease and move forward.
MyNarcolepsyTeam is the social network for people with narcolepsy and their loved ones. On MyNarcolepsyTeam, members come together to ask questions, give advice, and share their stories with others who understand life with narcolepsy.
Are you living with narcolepsy? Share your experience in the comments below, or start a conversation by posting on MyNarcolepsyTeam.