Overview of common sleep disorders
Sleep disorders affect more than 10% of the population. Effective treatments are available for some, whereas the cause and cure for others remain unknown.
- Sleep apnea. This periodic interruption of breathing, characterized by loud, interrupted snoring, affects more than 5% of adult males and can shorten lifespan more than smoking a pack of cigarettes a day. You can listen to an example of sleep apnea.
Sleep apnea is caused by the excessive relaxation of airway muscles during sleep. It can be effectively treated by wearing a mask that pressurizes the airway, a procedure called CPAP, or continuous positive airway pressure. In mild cases, weight loss and preventing sufferers from sleeping on their backs can help.
- Insomnia. This is even more common than sleep apnea. Sleeping pills can be helpful for short-term insomnia, but may not produce a longerm improvement, and may even have significant adverse effects, including shortening lifespan, when used frequently. Insomnia is more common later in life. The cause of this increase is unclear.
- Restless legs, PLM. One syndrome that is known to produce a profound insomnia is “restless legs with periodic movements during sleep.” "Restless legs" refers to an urge to move the legs that increases during quiescence. Periodic movement during sleep, a frequent accompaniment of restless legs, is a regular twitching, usually occurring every 5-90 seconds, usually in the legs, during nonREM sleep and can also disturb sleep. Periodic movement during sleep is present in as much as 10% of the adult population. Iron deficiency is a correlate and dopaminergic drugs can be effective in reducing symptoms
- Parasomnias. Night terrors, in which children scream during the night, sleep walking and bedwetting are some of the most common and are generally outgrown with age. Parasomnias include bruxism, a grinding of the teeth that can be treated by wearing a dental device.
- REM sleep behavior disorder. This disorder is characterized by vigorous movements occurring during REM sleep as the dreamer acts out his or her dream. The patient and those sharing the bed can be injured. Effective drug treatments, often using the benzodiazepine clonazepam, are available. REM behavior disorder often leads to Parkinson's disease.
- Narcolepsy. This disorder is characterized by excessive daytime sleepiness and by sudden loss of muscle tone in waking called cataplexy. The cause of most human narcolepsy has been identified in our laboratory (See Neuron, Thannickal et al, 2000, home page) and in other laboratories, as a loss of a chemical called hypocretin (also called orexin). The release of this chemical by a group of brain cells in a region called the hypothalamus normally helps maintain muscle tone and extend the duration of waking periods through its excitation of monoaminergic neurons, neurons containing the neurotransmitter acetylcholine and of other neuronal types. Joshi John and Frank Wu in our group have conducted a successful first test of hypocretin administration as a treatment for canine narcolepsy. Sam Deadwyler's group, in collboration with us, found that hypocretin administration reversed sleepiness in monkeys. We are hopeful that this treatment will be useful for human narcolepsy. Recently we have found a major increase in the number of histamine neurons in human narcolepsy, but not in animal genetic models of this disease (see Annals of Neurology, John et al., 2013, home page).