Adult humans spend about 1/3 of their lives sleeping. Sleep is that physiological change in the state of consciousness that involves adopting a resting posture, ceasing to react consciously to environmental stimuli or motor activity. It is a fully reversible state that serves the purpose of regeneration and rest.
Table of contents:
- Sleep - why is it so important?
- Sleep disorders - classification
- Sleep disorders - diagnosis
- Sleep disorders - types
Sleep - why is it so important?
During sleep, the secretion of growth hormone, or the number of cell divisions, increases. It is also the time for the consolidation of memory traces. And although the length and structure of sleep changes with age, it is not possible to do without it completely.
There are even studies indicating that too little or too much sleep per day is a risk factor for cancer, strokes and heart attacks.
All of this makes sleep disorders a significant clinical problem, causes great concern for sufferers, can cause significant economic losses (absenteeism from work, reduced efficiency, increased accidents), and provokes the creation of Sleep Medicine Centres, which are besieged by patients.
Sleep disorders - classification
Sleep disorders are also included in disease classifications. According to the ICD-10 classification in force in Poland, they are found in two chapters. Organic sleep disorders are coded in the chapter on diseases of the nervous system under the number G47.
Non-organic sleep disorders fall under the mental disorders section as F51. According to modern knowledge, this separation of the two does not seem justified.
The DS-IV TR classification of mental illnesses in America distinguishes primary and secondary sleep disorders:
- Secondary disorders may result from another primary condition (psychiatric or somatic illness), or be caused by the effects of previously ingested substances (stimulants, drugs).
- Among primary sleep disorders, a distinction is made between dyssomnias and parasomnias. In dyssomnias, the disturbance concerns the sleep itself, there is either too little sleep as in insomnias, too much, or there is excessive daytime sleepiness as in hypersomnias, or the abnormalities concern the circadian rhythm. In parasomnias, sleep is not disturbed, but there are abnormal events during sleep. Examples include somnambulism or night terrors. By definition, in parasomnias, the duration and quality of sleep remain unchanged, but anxiety and emotional tension occurring secondary to abnormal night-time events can also negatively affect the quality of sleep itself and lead to difficulty falling asleep.
Sleep disorders - classification, diagnosis, types, photo: shutterstock
The first international classification of sleep disorders was established as early as 1979, which can be linked to the beginnings of sleep medicine. However, the most detailed classification of sleep disorders was developed by the American Academy of Sleep Medicine. This is the International Classification of Sleep Disorders ICSD-2, published in 2005. It is also mentioned in ICD-10 in the section on non-organic sleep disorders.
While ICD-10 lists a few basic sleep disorders, in ICSD-2 we already find several hundred disease entities grouped into eight main categories. This classification distinguishes between:
- insomnia,
- sleep-related breathing disorders,
- hypersomnias,
- circadian rhythm disturbances,
- parasomnias,
- sleep-related movement disorders,
- other sleep disorders,
- sleep disorders affecting children.
Sleep disorders - diagnosis
Insomnia is diagnosed on the basis of symptoms subjectively assessed by the patient. There is no standard for a specific number of hours of nocturnal sleep below which the disorder is diagnosed. Typical patient complaints are that sleep is too short or not restful. Difficulties may involve any of the sleep phases and manifest themselves in difficulty falling asleep, maintaining sleep continuity (waking up during the night) or waking prematurely in the morning.
Sleep disorders - types
The most common sleep-related breathing dis orders are primary snoring and obstructive sleep apnoea syndrome. The latter disorder affects up to a few per cent of men and women and involves episodes of breath-holding lasting a minimum of 10 seconds with a subsequent drop in blood saturation and awakening. Patients usually do not remember these awakenings during the night, but the quality of their sleep deteriorates significantly.
Hypersomnia refers to excessive sleepiness. It can be related to physiological causes, medications taken or simply sleep deprivation. A particular sleep disorder in which excessive sleepiness occurs is narcolepsy, i.e. uncontrolled daytime sleep attacks. They are characterised by a sudden loss of muscle tone (cataplexy).
Sleep-wake rhythm disorders are most commonly delayed sleep phase syndrome and accelerated sleep phase syndrome. The former involves a delay in the time of going to bed compared to what is the social norm. This ailment particularly often affects young people, before the age of 30. In accelerated sleep phase syndrome, the preferred time to go to bed often starts before 9pm, leading people to wake up earlier, feel sleepy and have the urge to start activities at a time when most of society is asleep. This is a condition that most commonly affects people over 60. Circadian rhythm disorders often lead to complaints of excessive sleepiness or insomnia. No standard treatment has been established for disorders in this group.
Parasomnias are characterised by abnormal events during the transition from wakefulness to sleep or changes in sleep phases during sleep. Dozens of disorders in this category have been described. Among them, somnambulism, otherwise known as sleepwalking or sleepwalking, is the most common reason for seeking medical help, as well as night terrors; night terrors manifested by waking up from deep sleep with screaming; and REM sleep behaviour disorders, which occur due to an abnormality involving the maintenance of muscle tone during the REM phase by which dream content is enacted. With the exception of the last of these disorders, these parasomnias are typical of childhood.
On the other hand, the most common sleep-related movement disorder is restless legs syndrome, manifested by discomfort that forces one to move the legs. This disorder intensifies at night and occurs mainly in middle-aged people.