Narcolepsy
Narcolepsy is a neurological disorder that causes daytime tiredness and abnormal sleep patterns.
What is narcolepsy?
Narcolepsy affects people of all ages and seems to be a problem in five in every 10,000 people. It is quite difficult to diagnose and can cause some unusual problems in daily life.
How does normal sleep contrast with narcoleptic sleep?
|
Normal sleep |
Narcoleptic sleep |
|---|---|
| Most people sleep for around seven or eight hours each night | If you have narcolepsy, you usually only have broken sleep, and timing it is difficult. |
| It takes about 10 minutes to fall asleep. | People with narcolepsy typically take less than 5 minutes to fall asleep. |
| Each normal night-time sleep episode is cyclic, with each cycle lasting 90–100 minutes. REM sleep does not start straight away. | People with narcolepsy enter REM sleep immediately after they fall asleep. |
| Each cycle comprises 2 main stages: non-rapid eye movement (NREM) sleep and REM sleep. REM sleep occurs at the end of each cycle and lasts only a few minutes. Dreams occur but they are usually forgotten. Some can involve sleepwalking. | REM sleep is associated with dreaming and with relaxed muscle tone and ‘paralysis’. This is a defence against self-injury. If you ‘ran away’ during a nightmare, for instance, you might trip over furniture or fall down the stairs. |
Each cycle comprises two main stages: non-rapid eye movement (NREM) sleep and REM sleep. REM sleep occurs at the end of each cycle and lasts only a few minutes.
Dreams occur but they are usually forgotten. Some can involve sleepwalking. REM sleep is associated with dreaming and with relaxed muscle tone and ‘paralysis’.
This is a defence against self-injury. If you ‘ran away’ during a nightmare, for instance, you might trip over furniture or fall down the stairs.
What are the symptoms of narcolepsy?
The types of symptoms and how severe they are vary from person to person but most people with narcolepsy experience:
Excessive daytime sleepiness (EDS)
Brief episodes of daytime tiredness, followed by falling asleep. Each sleep episode typically lasts a few minutes or less. Some people with narcolepsy fall asleep without warning, literally falling to the floor unconscious. All people with narcolepsy have excessive daytime sleepiness at some point.
Cataplexy
Loss of muscular control while remaining conscious. This can affect the entire body, causing someone to fall over but not become unconscious, or only some parts. Cataplexy can be triggered by emotional events.
These may be ‘positive’, such as laughing a lot, or ‘negative’, such as stress. About 70% of people with narcolepsy have cataplexy.
Sleep paralysis
Being completely unable to move just after waking up. Sleep paralysis is often very distressing as the person affected may believe the paralysis is permanent.
Automatism
Continuing a routine activity, such as tidying a room, during an episode of daytime sleepiness. The person performing the activity is unaware of doing so, and the activity is usually done very badly.
This can be distressing – the person may ‘come to’ only to find that objects have moved ‘for no reason’, for example. Automatism may affect as many as 40% of people with narcolepsy.
Hallucinations
These are usually visual and can be vivid and frightening. The hallucinations may be hypnogogic or hypnopompic. The term hypnogogic describes a ‘dream-like’ state that can happen just before falling asleep; the term hypnopompic is a similar feeling that occurs just before waking.
These symptoms often affect people with narcolepsy in combination with disrupted night-time sleeping. Most people are troubled by waking up frequently during the night and symptoms often get worse in middle age, only improving some years later.
What causes narcolepsy?
Research has suggested that people with narcolepsy have lower than normal levels of neuropeptide hormones called hypocretins in the brain.
This is particularly the case when the narcolepsy is associated with cataplexy. Although narcolepsy is not primarily a genetic disorder, genetic factors obviously do play a role.
If a member of your family has narcolepsy, your risk of developing the disorder increases by about 10%.
It is also possible to develop narcolepsy if your brain is damaged. This can happen because of brain injury, tumours, drug abuse or infectious diseases.
Other chronic poor health caused by a bad diet, stress, poor sleeping habits, and hormonal changes can also be a factor.
Narcolepsy may also develop because of severe neurological disorders, such as Parkinson’s disease.
How is narcolepsy diagnosed?
Diagnosis is difficult. People with mild narcolepsy may never know they have it while severe cases are easily confused with other conditions such as epilepsy or sleep apnoea.
If you suspect you have narcolepsy, you should see your GP, who can arrange some tests that can lead to a formal diagnosis.
Two types of test are used – each involves monitoring brain activity, breathing rate, and heart activity.
Polysomnogram
This overnight test detects abnormal sleep activity. It allows narcolepsy to be differentiated from other conditions.
Multiple sleep latency test
This day test measures the time taken to fall asleep when catnapping and detects REM sleep and how quickly this occurs.