The rare condition narcolepsy causes persistent tiredness, ‘sleep attacks’ during the day, and in some cases, muscle weaknesses that can cause a person to collapse involuntarily.
Narcolepsy is a chronic neurological condition characterised by recurring periods of excessive sleepiness or lapses into sleep or napping within the same day (American Psychiatric Association 2013). It may also cause cataplexy (sudden involuntary muscle weakness or paralysis) (Brain Foundation n.d.).
Episodes of cataplexy may occur frequently and at any time, often triggered by strong emotions such as fear, anger, excitement or surprise. Attacks may happen during inappropriate moments including eating, talking or driving (Brain Foundation n.d.).
Narcolepsy is rare and estimated to affect about 1 in every 2,000 people, with onset generally during adolescence or early adulthood (though it can develop at any age). Symptoms may develop over a number of years (Sleep Health Foundation 2011).
How Does Narcolepsy Work?
A normal night of sleep will consist of several sleep cycles, each involving one period of NREM (non-rapid eye movement) sleep, then one period of REM (rapid eye movement) sleep. REM sleep generally begins after the first 60 to 90 minutes of sleep and is the window where dreaming will occur. During REM sleep, the muscles go limp so that the individual does not act out their dreams (NINDS 2019).
A person with narcolepsy, however, will enter REM sleep much earlier than the average person (sometimes within 15 minutes of falling asleep) and may suddenly enter into REM sleep or experience the associated muscle weakness during the day, or while still awake (NINDS 2019; Brain Foundation n.d.).
What Causes Narcolepsy?
Narcolepsy is caused by dysfunction of the sleep-wake regulators in the brain, though the reason why they function incorrectly in some people is not completely understood. It is thought that a very low level of the chemical ‘hypocretin’ (which regulates wakefulness) is the cause, as almost all people with narcolepsy who experience cataplexy lack normal levels of hypocretin (NINDS 2019).
However, those with narcolepsy who do not experience cataplexy usually have normal levels of hypocretin (NDIS 2019).
Risk Factors for Narcolepsy
Narcolepsy may be linked to:
Autoimmune disorders. Lack of hypocretin is thought to be linked to abnormalities in the immune system, wherein hypocretin-producing brain cells are wrongly attacked.
Genetics. Up to ten per cent of individuals with narcolepsy have a close relative with similar symptoms, but most cases have no known link to family history.
Brain injuries, tumours or diseases may interfere with the parts of the brain that regulate wakefulness.
Age. Narcolepsy can affect anyone but usually begins between the ages of 10 and 30.
(NDIS 2019; Mayo Clinic 2019)
Symptoms of Narcolepsy
All people with narcolepsy experience excessive sleepiness, but will not necessarily have other symptoms (Sleep Health Foundation 2011). These symptoms may include:
Excessive day sleepiness. This is the most common and obvious symptom. Even if the individual is well-rested, they will experience persistent sleepiness and ‘sleep attacks’ when they are otherwise alert.
Cataplexy. Sudden muscle weakness, thought to be linked to the limpness that occurs during REM sleep. It may range from weakness in only some muscles to complete collapse. Some people experience frequent episodes, while others only experience one or two in a lifetime. Not everyone who has narcolepsy experiences cataplexy. As cataplexy occurs in very few diseases, it can be a good indicator of narcolepsy.
Sleep paralysis, which is a temporary inability to move or speak during sleep or while waking up. Sleep paralysis usually only lasts for a brief period of time but can be distressing. People without narcolepsy can also experience sleep paralysis.
Altered REM sleep. People with narcolepsy may enter REM sleep more quickly than usual and during the day.
Hallucinations, which can be distressing.
Fragmented or disrupted sleep.
Automatic behaviour, wherein the individual falls asleep but continues the task they were in the middle of.
Other sleep disorders such as sleep apnea and insomnia.
(NINDS 2019; Mayo Clinic 2019; Sleep Health Foundation 2011)
According to the DSM-5, the following criteria should be met in order to diagnose narcolepsy:
Recurring periods within one day consisting of uncontrollable tiredness, lapses into sleep or napping. These should have occurred at least three times per week for the past three months; and
Evidence of at least one of the following:
Episodes of cataplexy at least a few times per month; or
Proven hypocretin deficiency as measured by cerebrospinal fluid; or
Nocturnal sleep polysomnography test demonstrating the onset of REM sleep in 15 minutes or less, or a multiple sleep latency test demonstrating an average sleep latency of 8 minutes or less and more than two sleep onset REM periods.
Narcolepsy is usually diagnosed through a combination of methods, including a laboratory test. Because symptoms can vary between people, and most of them (excluding cataplexy) could be falsely attributed to other conditions such as epilepsy, depression or chronic fatigue syndrome, laboratory tests can help rule out these other conditions (Better Health Channel 2014; SNORE Australia 2020).
Some diagnostic methods include:
Examination of sleep history, which can involve filling out the Epworth Sleepiness Scale test.
Keeping a sleep diary for a certain period of time.
Polysomnography. This is a test requiring an overnight stay at a medical facility. It involves measuring the electrical activity of the brain and heart, movement of the muscles and eyes, and breathing.
Multiple sleep latency test. This involves taking four to five naps every two hours during the day, with a specialist monitoring how long it takes to fall asleep.
(Mayo Clinic 2019)
Treating narcolepsy involves controlling the symptoms, as there is no cure for the condition. This may involve medication to help with sleepiness and cataplexy (Sleep Health Foundation 2011). Other strategies that may be helpful in managing symptoms include:
Scheduling short naps throughout the day;
Keeping a regular sleep schedule;
Avoiding caffeine or alcohol before bed;
Refraining from smoking;
Avoiding heavy meals before bed; and
Relaxing before bed and ensuring sleep space is comfortable.
It is extremely important to ensure symptoms are adequately controlled before undertaking activities where sleepiness could be dangerous (e.g. driving). Never drive if you are feeling sleepy (Sleep Health Foundation 2011; SNORE Australia 2020)