November 2002
Vol.9 No. 6

Editors: Dr. Elaine YW Kwan
Drs. Karen L Kwong, Sam SP Lau, KY Wong

ABC of Paediatric Sleep Medicine

Drs. Daniel KK Ng, Lettie CK Leung, Carrie Ka-li Kwok, Pok-yu Chow, Yu-ming Fu
Department of Paediatrics, Kwong Wah Hospital

Editor's Notes

Despite studies showing that sleep disorders are not uncommon in childhood and are associated with significant morbidity, functional impairment and decreased quality of life, inadequate attention is often paid by medical professionals to sleep disorders and their health consequences. In this issue, Dr. D Ng and colleague provide us with a brief summary of common sleep problems that may occur in children.



A 3-year-old child sleeps an average of 12 hours a day whilst a neonate sleeps an average of 17 hours a day. If an illness occurs randomly throughout the day, the chance of it occurring during sleep would be more than 50% in those aged less than 3-year-old. Hence, paediatricians should be well-informed about sleep and its associated problems. This article aims to provide a brief summary of common sleep problems for busy clinicians dealing with children.

Basic Facts about Sleep

Definition of Sleep

It is a sustained quiescence in a species-specific posture. It has quick reversibility to the waking state and involves characteristic changes in electroencephalogram (EEG).

Why Does One Sleep?

The exact function and reason for sleep is not well understood. However, it is known that total sleep deprivation results in mood changes, hallucination, illusion and paranoid behavior.

Normal Sleep in Children

In the first two decades of life, there is a substantial decrease in the total sleep time. In early childhood, total sleep time is less than that in infancy but is greater than that of adolescents. By 5 years of age, napping has largely ceased. Adult sleep pattern is usually achieved in early teens. The intrinsic sleep-wake cycle is about 24.2 to 24.4 hours in humans. This biological clock is controlled by the suprachiasmatic nuclei (SCN). The final sleep pattern in an individual results from interaction of extrinsic clues, e.g. sound, food, exercise, and the suprachiasmatic nuclei. Sleep consists of a number of sleep cycles. During each sleep cycle, there is rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. In the cycle, the child progresses from light sleep, stage I and II, to either deep sleep, stage III and IV (slow wave sleep) or REM sleep. Each sleep cycle lasts from 60 to 90 minutes. During REM, all striated muscles except the extra-ocular muscles and the diaphragm are paralyzed. This is important to prevent one from acting out of one's dream.

Sleep Disordered Breathing

These include primary snoring, upper airway resistance syndrome (UARS) and obstructive sleep apnoea syndrome (OSAS).

Primary Snoring

It is the inspiratory noise produced by vibration of the soft parts of the oropharyngeal wall during sleep. Ten percent of children snore habitually. Primary snoring is defined as snoring in the absence of abnormalities in ventilation, sleep architecture and daytime activities. Risk factors for snoring include deviated nasal septum, allergic rhinitis, hypertrophic turbinates, long, low and thick uvula, redundant tonsilar pillars, large tonsil and posteriorly displaced tongue. Management of snoring includes treatment of allergic rhinosinusitis with topical steroid and hypertonic saline nasal lavage, avoidance of sleep deprivation and sedative.

Obstructive Sleep Apnoea Syndrome (OSAS)

History and physical examination usually provide clues to the diagnosis. The clinical features of OSAS include snoring which is often continuous, daytime mouth-breathing, enlarged adenoid and tonsils, bizarre sleeping positions (e.g. neck hyperextension, knee-chest position), profuse sweating, obstructive hypoventilation with arousal on termination, hyperactivity, daytime sleepiness, failure-to-thrive, secondary nocturnal enuresis, nocturia and poor seizure control. Home videotaping and overnight oximetry/capnography are helpful as initial screening tools. Daytime nap study for a few hours is useful if abnormal. Overnight sleep polysomnography is the current gold standard for diagnosis of OSAS.

Polysomnography (PSG) is a simultaneous recording of a number of variables during sleep. It should be performed by a trained technologist. The routine PSG includes EEG channels to document sleep patterns, electro-oculogram to detect eye movement during REM sleep, chin electromyography (EMG) to detect atonia of REM sleep, leg EMG to detect limb movement, ECG, nasal/oral airflow sensors, thoracic/abdominal respiratory effort sensors, pulse oximetry and microphone to detect snoring.

Complications of OSAS include excessive daytime sleepiness, failure to thrive, pulmonary hypertension and systemic hypertension. Treatment of OSAS includes removal of tonsils and adenoids (T&A) or continuous positive airway pressure ventilation (CPAP).

Upper Airway Resistance Syndrome (UARS)

UARS refers to normal ventilation at the expense of increased inspiratory efforts. This increase in effort results in disruption of sleep leading to daytime disturbances, e.g. daytime sleepiness, poor academic performance. Indication for treatment of UARS depends on daytime symptoms. It includes T&A or/and treatment of co-existing allergic rhinitis.

Paediatric Insomnia

It can be divided into sleep-onset association disorder and limit-setting sleep disorder.

Sleep-onset Association Disorder

"Doc, little Johnny is driving me crazy as he cries whenever I put him down in his crib. I am so tired now. Please tell me what to do."

Sleep-onset association disorder refers to difficulty in falling asleep and difficulty in returning to sleep in the absence of specific environmental conditions. It usually affects those aged less than 2-year-old. The typical scenario is that the child has the habit of falling asleep with a person or object. These sleep associations make falling asleep independently difficult. When placed in the crib or bed after the child has fallen asleep, the child reawakens either immediately or later on and cries until they are in contact with a person or an object again. It becomes a problem to the parents in the following circumstances: 1) sleep onset is delayed, 2) frequent or prolonged attention is needed to help the child fall asleep, 3) the child's daytime mood or attention suffers, 4) parent-child relationships suffers or 5) parents are losing sleep.

The typical features are prolonged crying at bedtime or after awakening if parents do not respond in the usual manner but rapid sleep onset once the usual conditions are established. Parents should reinforce to the child that he/she is safe and comfortable even when alone. The best treatment for this disorder is to place the infant in bed awake for naps and sleep at night. If the child cries, they may return after a few minutes to comfort the child verbally but do not pick the child up and stay in the room for no more than 1-2 minutes. Gradual withdrawal should be initiated. It should be practiced in the following manner: parent can sit in a chair until the child falls asleep; the chair can be moved further and further away from the child until it is moved out of room with door open; followed by closed door.

Limit-setting Sleep Disorder

"Doc, Johnny stays up very late. He would ask for water or go to bathroom whenever he is asked to go to his bed. However, he would go straight to sleep when he sits next to us in the sofa."

Limit-setting sleep disorder refers to stalling behaviors or refusal to go to bed at the desired time, associated with lack of firm approach to a child's behaviour. The child is usually over 2 years and out of a crib. There are repetitive requests, complaints, and stalling despite physiological readiness for sleep. They frequently refuse to stay in bed or in the bedroom. There is no enforcement of consistent bedtime rules. There is possible recurrence of behaviors after nighttime wake-up. The sleep is usually of normal quality and duration. Management includes advice to parents about consistency and firmness in bedtime for children, establishment of routines leading to sleep and reinforcement of desirable behaviour with a star chart.

Delayed Sleep Phase Syndrome

It is seen in children of all ages. It is characterized by difficulty falling asleep at expected bedtime. It has a late but consistent time of sleep onset and difficulty to awakening at desired time. It is a normal sleep with a delayed schedule.


Phase Advance
Bedtime is initially set at the time when the child usually falls asleep. The child is woken up 30 minutes earlier than usual for a few days. This is followed by pushing the wake time to another 30 minutes earlier and so on. The aim is to achieve eventually the desired wake time. This would help advance the bedtime.

Light treatment
Bright light in the morning phase advances sleep onset for the following night but bright light in the evening phase delays sleep onset. Morning light should be administered immediately after waking up with intensity recommended at 2,000 lux (unit for light intensity) for 30-45 minutes.

Melatonin is secreted by the pineal gland and reaches peak concentration during sleep at night. Secretion of melatonin is inhibited by light. It may phase advance the major sleep period. Melatonin level is highest in children, then fall during puberty and further during adulthood. The quality of over the counter melatonin is highly variable and hence is not recommended. It should also be borne in mind that 1 mg of melatonin is a super-physiological dose.

Sleep Terror

Sleep terror is characterized by a sudden arousal from slow wave sleep with a piercing scream or cry, accompanied by autonomic and behavioral manifestations of intense fear. Violent behavior is common in sleep terror and injury is likely. There is often amnesia. The child is difficult to arouse and when aroused, is often confused on wakening. Sleep terror is uncommon. It usually involves stages 3 and 4 of sleep with onset usually within the first 90 minutes of sleep. Nightmares are different from sleep terrors in regard to their more common prevalence. It involves REM sleep and occurs in the second half of the night. Nightmares are less intense, with elaborate mental content. There is no violent behavior and patient is unlikely to be injured. The patients are easy to arouse, orientated on awakening and rarely amnesic.

Sleep terrors usually require no treatment. Parents should be reassured about the benign nature of sleep terrors and the tendency to resolve around 6 to 8 years of age. Avoidance of sleep deprivation and extension of sleep usually suffice. Parents may try to wake the child up before the usual time of occurrence of sleep terror. This disruption of sleep cycle may help decrease night terror. In exceptional cases, treatment with low dose clonazepam may be required, beginning at 0.25 mg one hour before bedtime.


It consists of a series of complex behaviors that are initiated during slow wave sleep and results in walking during sleep. Its onset is usually in the first 1/3 of the night. It is uncommon to have vocalization during sleepwalking. Automatism and awakening are less common. Confusion is usual. Usually no treatment is required. However, the environment needs to be made safe i.e., removal of sharp objects from the room, lock the main door, balcony door, and use window guard. In exceptional cases, treatment with benzodiazepines may be required.

Rhythmic Movement Disorder

This disorder consists of a group of stereotyped, repetitive movements involving large muscles, usually of the head and neck, which typically occur immediately prior to sleep onset and are maintained into light sleep. Different types of this disorder include head-banging, head-rolling, leg-rolling and body rocking. Most children do not require any specific treatment. Padding may be required to prevent injury. Psychosocial support can be helpful. Behavioral treatments give mixed success. Suppressant medications such as benzodiazepines may be helpful in some children.

Sleep Bruxism

It is a stereotyped movement disorder characterized by grinding or clenching of the teeth during sleep. The incidence is about 5% in adults but it occurs in over 50% of infants. The complications are dental damage with abnormal wear of the teeth, recession and inflammation of the gums, resorption of alveolar bone and temporomandibular joint (TMJ) disorders. Usually no treatment is required. Occlusal splints and dental reconstruction may be necessary in some patients.

Nocturnal Enuresis in Children

Nocturnal enuresis is defined as sleep bed-wetting for more than twice a month in children older than 5 years (mental age at least 4 year-old). It is called primary if the child has never been dry for more than 6 months. In the West, the prevalence is about 15-20% in 5 year-old, 7% in 10 year-old, 5% in 12 year-old and 1% in adult. In Hong Kong, available data suggest that the prevalence is about 2% in 5 year-old (Prof. Davis), 3.5% in 4 to 12 year-old (Yeung CK), 3.6% (for primary nocturnal enuresis) and 1.5% (for secondary nocturnal enuresis) in primary school children (Ng DK). Boys are affected more than girls. About 15% to 20% of cases spontaneously resolved per year. Twenty percent of affected children also suffer from daytime wetting (diurnal enuresis).

Primary nocturnal enuresis (PNE) is likely a multi-factorial disorder involving genetics, disordered anti-diuretic hormone circadian rhythm, bladder dysfunction as well as sleep dysfunction. As regards to sleep dysfunction, there is no consistent correlation between different sleep stages, arousability and enuresis. However others have found abnormal arousal thresholds and bladder contraction occurring without awakening. It has been suggested that PNE occurs when there is maturational delay in either of the two developmental processes, i.e. neurological control over bladder contraction and arousal response to bladder filling and contraction.

The aim of evaluation in children with nocturnal enuresis is to rule out organic diseases and to identify additional diurnal voiding dysfunction.

Investigations for isolated primary nocturnal enuresis (PNE) include urine for sugar, protein, microscopy and culture and early morning urine for osmolarity (>700 mosm/l exclude concentration defect). If there is symptoms suggestive of voiding dysfunction such as urgency, urge incontinence or frequency, urodynamic study may be needed.

Initial treatment for PNE is education. It includes reassurance, correction of family attitudes, removal of guilt, motivating the child, awareness of inconvenience, and explanation of the choice of specific treatment. General advice includes correction of constipation, restriction of fluids after dinner, emptying bladder before retiring and the use of star chart. If bladder instability is likely, anticholinergics and bladder exercises may be prescribed.

The star chart should be filled by the child (not by parent only), who is the active player. Encouragement and reward are given for dry nights, smaller wet patch, motivation and effort. Reward can be praise, stickers etc. A little (not too much) pressure improves learning. Neither punishment nor comforting is offered for wet event. It is important for child to be responsible for his bed-wetting and to deal with its consequences e.g. changing sheets. Parents should not routinely wake child to void.

Specific treatment includes moisture alarm and desmopressin. These treatments should be started earlier if the child is socially or emotionally affected. The timing depends on the child, severity of enuresis, the family and the doctor. It is usually required when the child is older than 7 year-old and bedwetting 2 to 3 times per week.

Moisture Mini-alarm (Conditioning)

It works by the principle of conditioning. It is our treatment of choice for motivated patients who can do as instructed. These patients should usually be older than 7 years, with a committed family that accepts disturbance by alarm sound at night. It works more slowly than drugs but the long term success rate is better. When it alarms, the child would stop voiding, stop the buzzer, and finish voiding in toilet. The child should change his underpants and reattach the enuresis alarm himself. For the first one to two weeks, parents may need to help out. It should be used with the star chart and smaller wet patches should be praised. The therapist needs to explain the anticipated response to the family, i.e. progressively smaller wet patches and 3 to 4 dry nights per week can be achieved by 3 to 4 weeks. After 28 consecutive dry nights, the fluid load can be increased and the alarm may be discontinued after another 28 consecutive dry nights. The success rate is about 65-100% (average 85%) after 4-6 months. The relapse rate is 9-23% (average 23%), most of those who relapse respond quickly to reusing the alarm. The success rate is enhanced by active support from parents & 2 to 3 weekly review by therapist.


It is a synthetic analogue of vasopressin. The usual oral dose is 200-400 microgram before bed. Response to treatment is usually immediate but most cases would relapse when the drug is stopped. There is still controversy over the duration of treatment. In our department, we use desmopressin for 3 months and then stop the drug to check for response.

Desmopressin is generally safe. Water intoxication and seizures have been reported. Other unwanted effects include headache, abdominal pain and nausea. Fluids should be restricted after dinner. Desmopressin is used for those who are poorly motivated to use the moisture alarm or those living in an overcrowded home rendering alarm too disturbing. It is also good for temporary use for sleep-overs or camps.

Choice of specific treatment depends on age of the child, motivation and ability of the child and the family and cost. When one therapy fails or is inadequate, one can change or add another therapy. For severe bedwetters, combined treatment may be considered.


In summary, sleep medicine has hitherto been neglected by paediatricians. Actually it involves a wide range of problems that, though not immediately life threatening, may be detrimental to the child's physical and psychological health in the long run. Also, "minor" sleep problems are common sources of concern and anxiety to the parent and to the whole family. Paediatricians may do well to start asking and addressing questions about their patients' sleep.

General references

  1. Ferber R, Kryger M. Principles and Practice of Sleep Medicine in the Child,1995.Philadelphia: W. B. Saunders.
  2. Kryger M, Roth T, Dement WC. Principles and Practice of Sleep Medicine, 2000. Philadelphia: W. B. Saunders.
  3. Koff SA. Cure of nocturnal enuresis: why isn't desmopressin very effecitve? Pediatr Nephrol 1996;10:667-70.


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