Sleep disorders and their clinical significance in children with Down syndrome
North American usage: mental retardation
Professor Gregory Stores at North Gate House, 55 High Street, Dorchester on Thames, Oxfordshire, OX10 7HN, UK. E-mail: email@example.com
Aim Our aim was to review basic aspects of sleep disorders in children with Down syndrome in the light of present-day findings of such disorders in children in general, including other groups of children with developmental disabilities.
Methods A literature search of adverse developmental effects of sleep disturbance, types of sleep disturbance in children with Down syndrome, their aetiology, including possible contributions of physical and psychiatric comorbidities and medication effects, principles of assessment and diagnosis, and treatment issues, was carried out.
Results Sleep disturbance is particularly common in children with developmental disorders including Down syndrome. Although there are just three basic sleep problems (sleeplessness or insomnia, excessive daytime sleepiness, and parasomnias) there are many possible underlying causes (sleep disorders), the nature of which dictates the particular treatment required. In children with Down syndrome, in addition to the same influences in other children, various comorbid physical and psychiatric conditions are capable of disturbing sleep. Possible adverse medication effects also need to be considered.
Interpretation Screening for sleep disorders and their causes should be routine; positive findings call for detailed diagnosis. Management should acknowledge the likely multifactorial aetiology of the sleep disorders in Down syndrome. Successful treatment can be expected to alleviate significantly the difficulties of both child and family.
Obstructive sleep apnoea
What this paper adds
- • This paper draws attention to the multifactorial nature of sleep disorders in children with Down syndrome.
- • Sleep disorders are linked with their origins, including comorbid conditions and medication effects.
- • Routine repeated clinical screening for sleep disorders and their possible causes is encouraged.
Considerable information and clinical guidance about children’s sleep disorders has been published in recent years.1 Basic points relevant to sleep disorders in children in general are that (1) such disorders are common (overall prevalence is estimated at about 25%2); (2) they take many forms (both physical and psychological), as demonstrated in the International Classification of Sleep Disorders;3 (3) sleep disorders are linked with various cognitive and behavioural difficulties in the child,4 adverse physical effects (including growth retardation, endocrine disorders, obesity, impaired immunity, and possibly cardiovascular problems5), and also parental problems, especially maternal stress;6 and (4) many types of treatment have been described from which an appropriate choice can be made, given an accurate diagnosis.7,8
Despite the availability of this information, the subject of sleep and its disorders has been neglected in public health education and also in professional education, including medical training.9 Parents’ basic knowledge about the importance of healthy sleep is often lacking10 with the result that sleep problems may well not be reported to family doctors;11 and often they are overlooked by paediatricians.12,13 Both poor recognition and misdiagnosis of the problem, as well as inappropriate treatment are likely to result from this lack of awareness and knowledge.14
These various considerations are relevant to all children with disturbed sleep, including (and sometimes especially) those with developmental disorders such as Down syndrome, although additional issues can arise with this group of children.
The prevalence of disturbed sleep is greater among children with neurodevelopmental disorders, such as Down syndrome, or other chronic paediatric or psychiatric conditions, than among children in general.15 As adequate, good-quality sleep is important for learning, notably attention and memory processes,16 sleep disruption in children with neurodevelopmental disorders may well exacerbate learning difficulties and disturbed behaviour that are the consequence of the developmental disorder itself.
Parents too can be adversely affected because of the extra burden imposed on them by their child’s poor sleep, and the disruption of their own sleep.17 Despite this, help may not be sought or adequately provided even in extreme circumstances18 such that opportunities for successful treatment are missed. In some cases, help for sleep disorders may not be sought or offered because it is believed that behavioural treatments for the sleep problems in children with a neurodevelopmental disorder are unlikely to be effective; this has been shown not to be the case.19
This paper reviews the basic aspects of sleep disorders in children with Down syndrome. Based on the findings in a US National Survey,20 it has been claimed that, compared with other children with special health care needs, those with this condition have a greater number of comorbid conditions, unmet needs (including those of a medical nature), and adverse family effects. Developmental and behavioural problems, as well as impaired quality of life, of children with Down syndrome have also been reported;21 the question arises, therefore, ‘What contribution is made by the children’s sleep disorders to these various difficulties?’
Reports of Sleep Disturbance in Children with Down Syndrome
Parents have consistently reported sleep problems in children with Down syndrome. In their 1982 publication Richman et al.22 concentrated on bedtime settling and night-waking problems, which they claimed were particularly common in the condition. Silverman’s 1988 review23 drew attention to obstructive sleep apnoea (OSA) in children with Down syndrome, soon after which details of the disordered respiratory physiology involved were reported.24 Since that time, surveys have consistently reported the three basic types of sleep problems,25–27 that is sleeplessness/insomnia, excessive daytime sleepiness, and parasomnias (unusual behaviours, experiences, or physical events associated with sleep). Features suggesting OSA are often mentioned. Daytime behavioural disturbance and maternal stress have been linked with these sleep problems.28
Sleeplessness/insomnia usually takes the form of difficulty settling to sleep at bedtime and/or troublesome waking during the night, or early-morning waking. In children, excessive daytime sleepiness can manifest itself as disturbed behaviour including attention-deficit–hyperactive disorder-type symptoms. Parasomnias, which take many forms, are commonly confused with each other, especially those of a dramatic nature.29
A recent comprehensive review of sleep disturbance in children with multiple disabilities by Tietze et al.30 included estimates of the relative prevalence rates (based mainly on parental reports) in various groups of children, including children with Down syndrome. Compared with the rate in typically developing children, overall rates reported for children with Down syndrome have varied from 31% to 54%. This increased rate was generally similar to that reported in other learning disability* syndromes (although particularly high rates are given for some neurodevelopmental disorders such as Smith–Magenis syndrome and, to a lesser extent, Angelman syndrome). These comparisons are interesting, but the relatively few studies (methodologically diverse in nature) on which the findings are based illustrate the need for more detailed enquiries concerned with sleep disturbance in neurodevelopmental disorders in general.
A parental report that their child has a sleep problem is only the starting point in the process of providing help and advice; identification of the child’s sleep disorder is required. The distinction between sleep problems and sleep disorders is crucial although not always appreciated. There are the three basic sleep problems, as mentioned above, but over 80 sleep disorders (i.e. possible underlying psychological or physical causes of these sleep problems) are now described in the International Classification of Sleep Disorders.3 Choice of treatment and also prognosis depends essentially on the child’s sleep disorder, not the reported problem. Attempts to treat the problem without accurate diagnosis of the underlying cause are likely to be unsuccessful.
Children with developmental problems (including those with Down syndrome) do not have an overall separate set of sleep disorders from other children. The differences can lie in (1) the relative frequency of occurrence and balance between the different sleep disorders, (2) the clinical manifestations of basically the same type of disorder; (3) the degree of severity, and (4) (if untreated) the persistence of the problem in the developmentally compromised child.
In making a diagnosis of a sleep problem in a child with Down syndrome the following possible causes need to be considered: (1) the same factors that can apply in any child with disturbed sleep, (2) comorbid conditions of a physical or psychiatric nature (to which children with Down syndrome are especially prone), each of which is capable of giving rise to a sleep problem, often of serious degree (see Stores and Wiggs15 for details), and (3) medication effects.
Aetiology of Children’s Sleep Disorders
A wide range of factors (behavioural, medical including pharmacological, and psychiatric) can underlie children’s sleep disorders.1 A few examples illustrate that these vary with the age of the child. First, in very young children a degree of early brain maturation is required for the biological clock controlling sleep–wake rhythms to develop.31 Second, parenting practices can profoundly influence young children’s sleep patterns: lack of routine, poor limit setting, and reinforcement by paying too much attention to a child’s reluctance to settle to sleep can cause or maintain sleep problems (so-called ‘behavioural insomnia of childhood’32 as distinct from insomnia as a result of other causes). Finally, adolescent sleep difficulties33 may well be caused by a combination of pubertal changes in sleep physiology and altered lifestyle (including late-night social activities), as well as emotional problems concerning everyday matters. At any age, the possibility of medical factors associated with sleep problems needs to be considered.15,34
There may be additional considerations concerning children whose development is delayed. For example, a child’s intellectual limitations or communication problems may interfere with the acquisition of good sleep habits. Parenting practices and capabilities feature prominently in the origin, severity, or maintenance of childhood sleep disturbance, which is generally closely associated with parenting stress.35 Because of the various pressures of bringing up a child with development delay, especially without practical advice and support, parents’ mental health and relationships are likely to suffer, as are their parenting abilities, including their ability to cope with their child’s sleep problems. Moreover, the comorbid physical and psychiatric conditions associated with Down syndrome discussed below need to be considered as possibly contributing to sleep disturbance.
Physical Comorbidities in Down Syndrome Associated with Sleep Disorders
Charleton et al.36 list a total of 44 specific medical problems that occur more frequently in people with Down syndrome. Not all of these problems are particularly associated with sleep disturbance, but many are.15 These include OSA, cardio-respiratory problems, painful or otherwise uncomfortable conditions (such as those of musculoskeletal origin or due to skin disease), gastro-oesophageal reflux, thyroid dysfunction, severe visual or hearing loss, obesity, and epilepsy.
OSA deserves special mention. It is reported to be a complication in 50% or more of children with Down syndrome,37 and to have many potentially serious cognitive, behavioural, and other medical consequences (summarized by Rosen38). These are largely due to the disruptive effect of OSA on sleep (‘fragmentation’), which impairs its quality and restorative value. There is some evidence that the sleep of children with Down syndrome is further fragmented beyond that attributable to OSA.39 Although the clinical features of OSA episodes themselves are well described, these wider adverse effects may be misinterpreted as inevitable and immutable aspects of Down syndrome (or, for that matter, other learning disability syndromes complicated by OSA, of which there are a number15).
Children with Down syndrome are subject to the range of parasomnias that occur in children in general. However, in view of the prominence of OSA in Down syndrome, further parasomnias associated with this condition can be anticipated. This possibility has received little attention in the Down syndrome literature. Schenck and Mahowald40 have reviewed the range of parasomnias that have been associated with OSA (mainly in adults). Reference is made to OSA triggering arousal disorders (sleepwalking, sleep terrors, and confusional arousals) in children. Nocturnal enuresis41 and bruxism42 are other possibilities. High rates of the latter have been reported in children with Down syndrome but seemingly with no greater frequency than in other children.43 The importance of recognizing such parasomnias is that successful treatment of the OSA is reported to reduce their occurrence.40
Psychiatric Comorbidities in Down Syndrome Associated with Sleep Disorders
Further comorbidities of Down syndrome capable of disturbing sleep are those of a psychiatric nature.21,44 Examples described in the literature are anxiety states, depression, conduct disorder, and attention-deficit–hyperactivity disorder,45 as well as autistic spectrum disorders.46 Sleep disturbance associated with each of these psychiatric conditions are described elsewhere.47 It goes without saying that it is important that these psychiatric disorders are recognized and treated in the general interests of the child and the family as a whole, and for the improvement in the child’s sleep.
Effects of Medication on Sleep
Various medications used in paediatrics have been associated with sleep disturbance of one sort or another.48 Examples include stimulant drugs for attention-deficit–hyperactivity disorder, pseudoephedrine and theophylline (sleeplessness), and sedative–hypnotic drugs including benzodiazepines and some antihistamines, major tranquillizers, and some antiepileptic drugs such as barbiturates, valproate, and carbamazepine (excessive sleepiness). It seems less well known that some drugs (e.g. zolpidem and some antidepressants) have been linked with the occurrence of parasomnias, especially sleepwalking, although some doubt has been expressed about the strength of this association.49
In the light of the above considerations, a thorough analysis of the cause(s) of a child’s sleep problem is essential. Treatment of a sleep disturbance should not precede diagnosis of the underlying cause, of which there are many possibilities in children with Down syndrome.
That said, it cannot be assumed that the child’s sleep problem has already come to attention. Parents may not seek help for even grossly disturbed sleep patterns in the mistaken belief that it is an inevitable and untreatable part of their child’s developmentally delayed condition.18 For that reason, it is appropriate to screen all children with Down syndrome for sleep disturbance (the same applies to children with other forms of developmental delay and the other high-risk groups mentioned earlier).50 It is appropriate to repeat such screening periodically as sleep disorders might arise as development proceeds.
Routinely, history taking should at least include basic enquiries about bedtime difficulties or settling to sleep, waking during the night, breathing problems while asleep, difficulty waking up in the morning, being sleepy or ‘overtired’ during the day, and unusual behaviours, experiences, or movements at night. Especially if the answers are positive, there is merit in collecting further details by means of a brief standardized screening questionnaire.
Tietze et al.30 also analysed sleep questionnaires that have been used to assess children’s sleep. Many had not been adequately evaluated psychometrically and/or were clinically limited in scope or predictive value. The authors stress the need to develop more satisfactory instruments. The same point has been made by Spruyt and Gozal51 in their comprehensive review of currently available paediatric sleep questionnaires in the light of their mainly psychometric criteria for the satisfactory design of such tools. Although not meeting as many of these criteria as some other questionnaires, the Children’s Sleep Habits Questionnaire is worth considering as a brief screening questionnaire because of the range of sleep problems that it covers and its versions for both toddlers to preschool children52 and school-age children.53 It has been used with typically developing children and also others of different ages whose development is delayed.
However, screening for sleep symptoms simply highlights the possibility of a sleep disorder and does not constitute a diagnosis. Adequate identification of a sleep disorder requires comprehensive clinical enquiry consisting of detailed histories especially about the sleep problem, the child’s 24-hour sleep–wake pattern including parenting practices, developmental details, family history, and family circumstances.54 Both physical and behavioural examination may well be appropriate, and possibly further assessment in the form of sleep diary records and objective sleep studies such as actigraphy or polysomnography. Referral for assessment at a specialist paediatric service or sleep disorders clinic may be needed. The Royal College of Paediatrics and Child Health report37 recommended regular screening for overnight hypoxia in infants with Down syndrome until the age of 5 years.
Although it might be thought unlikely that the physical and psychiatric comorbid conditions mentioned above will have been overlooked, this might not be so. Therefore, the child’s overall physical and psychiatric condition may merit comprehensive review not only initially but, again, at intervals. Similarly, the possibility of medication effects should be monitored.
In general, reliance can be placed on the treatments recommended for children’s sleep disorders in general, with the caveat that formal evidence for their efficacy is limited, as yet.7
The main aspects of such treatments for children’s sleep disorders are education of parents, including principles of sleep hygiene to help encourage good sleep habits;55 behavioural methods, mainly for sleeplessness/insomnia;19 and pharmacological treatments in a limited number of circumstances, including when behavioural methods have failed (although the place of medication in these circumstances requires further study56,57). Other treatments are described elsewhere;1 these include chronotherapy for sleep–wake cycle disorders, and physical methods such as adenotonsillectomy, continuous positive airway pressure, and weight reduction for OSA.
Special considerations in the case of children with Down syndrome include the fact that, as discussed by Rosen,38 conventional surgical treatment for OSA can be of limited efficacy in children with Down syndrome and more recently developed approaches may be required (assessment and interventions have been considered in the Royal College of Paediatrics and Child Health report37). The point has already been made that attention (as far as possible) to certain comorbid conditions and also to possible medication effects may well improve sleep. A convincing connection between the introduction of medication (or an increase in dosage) and the onset of a sleep problem calls for adjustment of the dosage, alteration of its timing or substitution of an alternative form of treatment. Regarding behavioural treatment for sleeplessness/insomnia in children with Down syndrome, administration by means of group instruction for parents has been reported to be effective.58
In addition to the accurate identification of sleep disorders and the correct choice of treatment, success (hopefully demonstrated to be long-lasting) will depend on parents’ preference, capabilities, and commitment, the child’s willingness and ability to comply, and an adequate trial of treatment. Sustained support and guidance is likely to increase the chance of a good outcome.
The approach and attention to detail required in identifying the origins and appropriate treatment of sleep disorders in children with Down syndrome are amply justified in view of the benefits to the children and their families that should accrue. The basic syndrome may not be alterable but, in principle, attention to the issues described above can be expected to improve the child’s developmental status and general circumstances.