Aetiology
Chronic insomnia disorder usually presents with perceived difficulties in initiating or maintaining sleep that require interventions by parents or other carers in order to overcome them.
These can include sleep-onset difficulties which typically develop when the child comes to associate falling asleep with a specific stimulus (such as being held, stroked, nursed, or sung to) from carers, and becomes unable to self-soothe to sleep.
Limit-setting behaviours typically involve a child testing the limits of what his/her parents consider acceptable behaviour. The child may stretch the boundaries set by parents in ways that subsequently become difficult for the parents to sustain and/or to roll back. A lack of consistency in parenting styles between the parents can send mixed messages to the child and create an unstructured sleep environment, resulting in the child not understanding what the limits are and disregarding them. The child typically utilises stalling and delaying tactics in trying to put off going to bed, such as asking for another kiss goodnight or another drink of water, or refuses to stay in bed and/or migrates to the parents' bed during the night.[5][9]
Delayed sleep-wake phase disorder (DSWPD) may be triggered in part by structural changes in the brain, known as synaptic pruning, which occur during adolescence. In general, adolescents tend to delay their sleep phase.[5] Without external cues to entrain their internal circadian body clock, adolescents tend to delay their sleep phase and adopt a circadian rhythm that is >24 hours.[41] DSWPD is often brought on by a combination of poor sleep hygiene and external pressures such as school work, bedroom distractions, use of electronic media, social engagements, and sports activity.[42] These all delay sleep onset. Insufficient sleep during the week is coupled with a tendency to sleep in late on weekends in order to catch up on lost sleep, which in turn delays the circadian phase. The syndrome may also stem from a heightened sensitivity to evening light exposure, and in some cases from genetic differences in clock genes.[43][44][5]
Obstructive sleep apnoea (OSA) occurs when the upper airways collapse during inspiration while the child is asleep, and is a multifactorial disease. Contributing factors include:[45][46][47][48][49][50][51][52][53][54][55]
Interplay of craniofacial dimensions: maxillary hypoplasia, retrognathia, micrognathia, and congenital syndromes associated with craniosynostosis all reduce the aperture of the upper airway and narrow its calibre
Enlarged soft tissue (primarily the adenoids and tonsils)
Macroglossia
Inflammation of soft tissue such as occurs with gastro-oesophageal reflux, allergic rhinitis, and exposure to irritants such as environmental tobacco smoke
Fat deposition in the neck as occurs in obesity
Low baseline muscle tone
Changes in muscle tone induced by alcohol and certain medications, as well as certain genetic disorders. For example, Down's syndrome is particularly associated with development of OSA.[22]
Pathophysiology
Inspiration is triggered by a signal from the respiratory centres in the brain stem to the muscles of respiration, resulting in air being sucked inwards through the upper and lower airways. During sleep, there is a reduction in muscle tone and the calibre of the upper airway diminishes. In obstructive sleep apnoea (OSA), this can cause a reduction in airflow, sometimes to the point where it ceases entirely. Depending upon the degree of flow limitation, its duration, and associated consequences, the events can be classified as primary snoring, respiratory effort-related arousal, hypopnoeas, or apnoeas.[56] Based upon the degree of obstruction present, a diagnosis can be made of primary snoring; upper airway resistance syndrome; chronic obstructive hypoventilation; and mild, moderate, or severe OSA.
Classification
The international classification of sleep disorders (3rd edition) (ICSD-3-TR)[5]
This is the principal classification manual of sleep disorders, published by the American Academy of Sleep Medicine, including taxonomy, diagnostic criteria, and differential diagnoses, with linkage to ICD-10-CM and ICD-11 codes.[5] It subdivides the various sleep disorders into the following categories: insomnia, sleep-related breathing disorders, central disorders of hypersomnolence, circadian rhythm disorders, parasomnias, sleep-related movement disorders, isolated symptoms, normal variants, and other sleep disorders. Disorders relevant to this topic include chronic insomnia disorder (previously behavioural insomnia of childhood), obstructive sleep apnoea, narcolepsy, delayed sleep-wake phase disorder, and inadequate sleep hygiene.
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