A good sleep is essential for optimal health. A sleep disorder is a set of conditions that frequently disrupts a quality sleep.
Classification of sleep disorders
The most widely accepted classification system for sleep disorders is that of International Classification of sleep disorders (ICSD). The third edition of ICSD classifies sleep disorders into seven major categories:
- Sleep related breathing disorders
- Circadian rhythm sleep wake disorders
- Central disorders of hypersomnolence
- Sleep related movement disorders
- Other disorders of sleep
It is again further divided into many subtypes
There are three types of insomnia:
- Chronic insomnia disorder: a person should have symptoms for more than three times per week and that too for over a period of more than three months
- Short – term insomnia disorder: if symptoms are present less than three months. It usually develops because of a specific stressor.
- Other insomnia disorder
Parasomnia is a condition of undesirable behavior, emotions or experiences that occur during entry, arousal or during the sleep. Parasomnias are categorized into:
- Rapid eye movement related parasomnia (REM): include sleep paralysis and nightmare disorder. Diagnosis is based on the occurance of repeated episodes of such events.
- Non – rapid eye movement related parasomnia (NREM): are disorders of arousal including sleep walking, confusional arousals and sleep terrors.
- Other parasomnia: they have no relation with the sleep stage. They include parasomnia due to medication or substance or mental disorder, sleep enuresis, sleep related hallucinations and exploding head syndrome.
Sleep related breathing disorders
They are characterized by abnormal breathing during sleep. They are classified into:
- Obstructive sleep apnea disorders: it is chronic condition in which the patients are have a very poor neurocognitive performance due to repeated arousals over several months to years.
- Sleep related hypoventilation disorders: it occurs due to elevated PaCO2
- Central sleep apnea syndromes: are a group of disorders of decrease of airflow and ventilation during sleep. It is common in general population.
- Sleep related hypoxemia disorder: is characterized by a sustained drop in the arterial oxygen levels.
Circadian rhythm sleep – wake disorders
This is a chronic sleep disturbance that occurs either due to alteration of circadian rhythm or due to misalignment of persons sleep wake system. This is subdivided into:
- Jet lag disorder: also known as shift worker disorder.
- Delayed sleep wake phase disorder: characterized by a difficulty in falling asleep and is awaken late in the morning
- Advanced sleep wake phase disorder: the persons falls asleep too early and wake up early in the morning
- Irregular sleep wake rhythm disorder: it is characterized by an underdeveloped circadian rhythm
- Non – 24 hour sleep wake rhythm disorders: it is characterized by a fluctuating periods of excess sleep and insomnia
- Disorders of circadian rhythm due to neurologic or psychiatric conditions
Central disorders of hypersomnolence
These sleep disorders are those in which there is an excess day time sleepiness which occurs independent of any other sleep disorder. They include:
- Narcolepsy: it is a disorder of excessive sleepiness along with cataplexy or/and hypocretin – 1 deficiency.
- Idiopathic hypersomnia: has a mechanism that is not well understood. It is often associated with difficulty in waking up from day time naps or nocturnal sleep.
- Kleine – Levin syndrome
- Other hypersomnias
Sleep related movement disorders
They are often associated with simple, stereotypic movements that disturbs and spoil the sleep. They include:
- Restless legs syndrome: a strong urge to move the legs due to an uncomfortable sensation at rest.
- Periodic limb movement disorder: it is usually noted during polysomnography.
- Sleep related bruxism:
- Sleep related cramps
- Sleep related rhythmic movement disorder
- Propriospinal myoclonus at sleep onset
- Benign sleep myoclonus of infancy
- Due to a medical disorder
- Due to a substance or medication
Other sleep disorders
The disorders of this category overlaps with other disorders of sleep and the data is insufficient to establish a diagnosis. Sleep disturbance due to environmental disturbance is also categorized here.