For the purpose of this article, when we discuss diseases of sleep, we are not talking about sleeping disorders like narcolepsy or insomnia. Instead, we are talking about diseases that are caused by or a result of some factor or characteristic relating to sleep.
It has long been known that problems related to sleep play a significant role in a large number of disorders. Many medical problems such as asthma attacks and strokes, occur more often throughout the night and into the early morning. It is thought that this may be related to some of the facets of sleep including things like hormone and heart rate changes.
In studies, we have seen how the different stages of sleep - non REM and REM sleep - can affect epilepsy patients. It seems that deep sleep might actually promote the spread of seizures while being deprived of sleep can trigger seizures in people with certain types of epilepsy. Sleep deprivation has also been known to be connected to heart disease. In addition, studies have also shown that sleep deprivation has been connected to certain mental illnesses such as bipolar disorder and psychosis. A 2007 study using MRI technology, performed at the Harvard Medical School, showed that when lacking sleep, the brain has difficulty dealing with emotional events - oftentimes being unable to put them into the right frame of reference. This results in a person's inability to react properly to the event, being unable to create a suitable response.
If you've ever had the flu before, you're aware that these types of infectious diseases make us feel tired. Cytokines, the chemicals produced by our immune system to fight off these infections, are very strong sleep-inducers. This feeling of sleepiness is thought to happen because the body is using sleep to conserve energy and recharge itself. And this is done in preparation for your immune system's attack on the infectious invaders.
Sleeping problems seem to be a byproduct of almost every mental disorder - including people with schizophrenia and depression. For people suffering from depression, they often find themselves waking up in the middle of the night, unable to find their way back to sleep. Ironically, sleep deprivation is sometimes used as an effective way to combat depression in certain cases while in others, sleep deprivation can be the cause of their depression. And in extreme cases of sleep deprivation, people have been known to experience hallucinations and states of paranoia. In people suffering from manic depression, sleep deprivation has been known to be the catalyst, triggering hyperactivity and agitation (manias).
Problems associated with sleep can be associated with a multitude of infections, diseases and disorders. Patients with neurodegenerative disorders such as Alzheimer's and Parkinson's have been known to experience severe sleeping problems. Other disorders where the inability to get or stay asleep becomes a problem are in cases of stroke and cancer patients and for people who experience some type of head injury or trauma. The problems these people experience while trying to sleep are thought to be caused by the neurotransmitters that control sleep or from the drugs they're prescribed. What's worse is that patients who experience sleeping problems due to their condition usually experience frustration, depression or bouts of confusion as well as an increase in pain levels. This in turn leads them to increase their dosages of pain medication, thereby making it more difficult to get quality sleep.
There are two types of 'sleep diseases' that are less common around the world and get their names from the effects of the disease rather than being caused by anything related to sleep.
One is commonly called Sleeping Sickness which is prevalent in some regions of sub-Saharan Africa. Also called Human African trypanosomiasis, Congo trypanosomiasis or African lethargy, this disease is so named because of the extreme fatigue people feel after they contract the disease. Sleeping sickness is transmitted by the tsetse fly and people bitten and infected by the fly will experience symptoms including fatigue, bouts of insomnia, periods of mania, reduced co-ordination and increased confusion. The disease is fatal without treatment as the progression of mental deterioration will eventually lead to a coma and then death.
The other sleep disease carries the nickname Sleepy Sickness but is also sometimes called (and confused with) Sleeping Sickness. The proper name being Encephalitis Lethargica, an epidemic spread around the world between 1915 and 1926 without another epidemic since being reported. The cause of sleepy sickness is not known for certain but the symptoms are severe and include sore throat, double vision, high fever, slow mental and physical response, headaches , lethargy and catatonia. And in more acute cases, a coma-like state called akinetic mutism. Fortunately, very few cases of sleepy sickness have since been reported.
Sleepy sickness has also been the subject of several books, T.V shows and movies including the 1990 movie Awakenings, starring Robin Williams and Robert de Niro.