Occasionally we come across people who complain of feeling sleepy throughout the day and who fall asleep very easily during the day as if they have never had enough sleep. This is called excessive daytime sleepiness or EDS. EDS sufferers do not normally include people who have insomnia and feel sleepy. The chief complaint of people who have insomnia is their inability to sleep and the distress of lying awake at night, whereas people with EDS appear to have a compulsion to sleep even if they have been sleeping at night. There are two main causes of EDS: narcolepsy and sleep apnoea.
Narcolepsy. This is the most interesting cause of EDS. People suffering from narcolepsy have sleep attacks and are chronically sleepy. They cannot resist sleep and sleep comes abruptly, sometimes in the most embarrassing or hazardous circumstances. They can fall asleep while driving for short distances or even when they are operating dangerous machines. It has been reported that they can even fall asleep whilst having sex, when the body should be pumping hard with adrenaline. This condition results from a developmental defect in the brain, present at birth, and is most prominent at around 20 years of age.
It is not infectious. Narcolepsy is sometimes associated with other phenomena, namely cataplexy, hypnogogic hallucination, and sleep paralysis:
* Cataplexy is a sudden paralysis of some part of the body. This can be brought on by the sudden expression of emotions, such as laughter, excitement, anger, or extreme pleasure. This is the reason why a person suffering from narcolepsy can become paralysed with sleep when he is about to climax during sex.
*In hypnogogic hallucination, a person sees things before he is fully awake from sleep. The word hypnogogic comes from ‘Hypnos’ the name of the Greek god of sleep. It is a mixed feeling of dreaming and being awake at the same time. It can be an experience of seeing things that do not exist, but the person is convinced that he is awake.
*Sleep paralysis is much more common. Most of us experience it occasionally. For instance, you are still in bed, you think you are awake, and you can see the room you are in. You may be able to move your eyes, but the body is completely paralysed and immobile. Usually when this happens you are in a transitional state between dreaming and reality; that is, you are in the process of waking up from a dream. The experience can be frightening.
As we have already learnt, when we are in REM sleep our body is completely paralysed, as if there is a jamming mechanism that prevents our limbs from moving. When we are sleeping it does not worry us, because we are not aware of the paralysis. However, when we are semi-awake and aware of the inability to move our limbs, we are gripped by a terrible feeling of imminent catastrophe and panic follows. One patient told me about her husband who had frequent sleep paralysis. He made so much noise in his throat during an attack that she knew he was in trouble. But once she touched him he would wake up and immediately feel incredible relief. The husband told me that during an attack he always thought he was going to die, as he could not move at all. He believed a ghost was sitting on top of him, immobilizing him.
Cataplexy, hypnogogic hallucination, and sleep paralysis are all a disorder in REM sleep, namely that REM sleep occurs too quickly and too often. Sleep comes easily and quickly, and REM sleep may occur within ten minutes of falling asleep. During REM sleep the mind is actively dreaming, but the muscle tone of the body is flaccid. Cataplexy and sleep paralysis both result from this loss of muscle tone, whereas hypnogogic hallucination is associated with the actual experience of dreaming during REM sleep.
People who suffer from narcolepsy should never drive long distances or engage in hazardous work. Accidents are common among the narcoleptics, and they find it difficult to hold onto a
steady job as their bosses generally dismiss them for sleeping on the job. When a narcoleptic patient is tested in the sleep laboratory, an excess of REM sleep is recorded, especially immediately after falling asleep. Medical treatment with a stimulant called amphetamine, which has to be taken regularly, can be successful.