Sleep disorders in people with intellectual disability

Sleep problems are common in people with intellectual disabilities, with the prevalence of sleep problems in children ranging from 24% to 86%.^{Reference van de Wouw, Evenhuis and Echteld2,Reference Richdale and Baker10–Reference Hylkema and Vlaskamp13} The estimated prevalence of sleep disorders in adults with intellectual disabilities ranges from 8.5% to 34.1%, with 9.2% experiencing significant sleep problems.^{Reference van de Wouw, Evenhuis and Echteld2} Van de Wouw et al^{Reference van de Wouw, Evenhuis and Echteld2} found that 72% of 551 older adults with an intellectual disability had sleep difficulties.

Mental and physical health disorders and their treatment in people with intellectual disabilities represents an under-researched area. Diagnostic and management strategies are commonly adopted from studies undertaken in people without intellectual disabilities. Sleep disorders in adults with intellectual disabilities follow the same pattern. Richdale et al^{Reference Richdale and Baker10} described the disappointing lack of research specifically concerning the aetiology and impact of sleep difficulties and the corresponding interventions in those with developmental disorders. Understanding the types of sleep problems that adults with intellectual disabilities experience and the many factors that influence their sleep can inform the assessment and management of sleep problems in adults with intellectual disabilities.¹⁴

There are several potential explanations of why adults with intellectual disabilities are more likely to experience sleep problems. A systematic review of the published literature on sleep disorders in adults with intellectual disabilities by Van de Wouw et al^{Reference van de Wouw, Evenhuis and Echteld2} reported associations between sleep and several factors, including challenging behaviour, psychotropic medication, mental health conditions and respiratory diseases. To provide person-centred and individualised care, it is important to understand and consider the biological, psychological and social factors contributing to the increased prevalence of sleep problems in adults with intellectual disabilities (Figs. 1 and 2). We have explored several important contributing factors that should be considered when assessing sleep difficulties in adults with intellectual disabilities.

Fig. 1 Factors affecting sleep in people with intellectual disabilities (ID).

Fig. 2 Examples of factors affecting sleep in people with intellectual disabilities (ID).

Diagnosing sleep disorders

Although there are guidelines on the diagnosis and management of sleep disorders in the non-intellectual-disabilities population,^31,32 intellectual-disabilities-specific guidelines are lacking. More often than not in adults with intellectual disabilities, subjective sleep information is provided by carers, who may have differing opinions on the level of sleep disturbance or may even simply accept sleep disturbance as part of the person's underlying condition.^{Reference Surtees, Oliver, Jones, Evans and Richards33} Consequently, sleep disorders are likely to be brought to clinician's attention when they lead to nocturnal and daytime dysfunction, including behavioural disturbance, rather than because of their impact on the person's subjective opinion of their quality of life.^{Reference McPherson, Kaushal, Kothapalli and J34} Questionnaires such as the Insomnia Severity Index^{Reference Morin35} can be used to assess severity and monitor response to treatment, but they are rarely validated in people with intellectual disabilities and rely more on carers’ reports.

Guidelines aimed at the general population emphasise the importance of looking for comorbid medical conditions when assessing sleep disorders.³² This is arguably even more important in individuals with intellectual disabilities, who are more likely to have a physical health condition such as OSA or epilepsy which affects their sleep.^{Reference de Carvalho, Amorim, Santana, de Almeida, Santana and de Neves36–Reference Trois, Capone, Lutz, Melendres, Schwartz and Collop38} For example, owing to the high prevalence of OSA in individuals with Down's syndrome, it is recommended that everyone with Down's syndrome is screened for this condition.^{Reference de Carvalho, Amorim, Santana, de Almeida, Santana and de Neves36}

Sleep diaries completed by carers and/or actigraphy, ideally undertaken for a minimum of 2 weeks, can be used when sleep–wake timings (including napping) are inconsistent or unreliable.^{Reference Lawrence and Muza39} Home or in-patient sleep investigations (for example, pulse oximetry or the gold-standard, polysomnography) can be used to investigate physical sleep disorders such as OSA and nocturnal epilepsy in people with intellectual disabilities.^{Reference Rundo and Downey40} While these investigations should always be offered when clinically appropriate, a pragmatic trial of treatment may sometimes be required when sleep investigations are not tolerated by the individual.

In Fig. 3, we outline a suggested approach for the assessment and management of sleep disorders in adults with intellectual disabilities, based on our collective clinical experience.

Fig. 3 Flowchart for screening, assessing and managing sleep disorders in adults with intellectual disabilities (ID). GP, general practitioner; MDT, multidisciplinary team.

Management strategies for sleep disorders in people with intellectual disabilities

The management of sleep disorders is complicated by the heterogeneity of the underlying causes of intellectual disabilities, along with the nature of associated comorbidities. Ideally, each of the factors outlined in Fig. 1 should be addressed in order to optimise sleep, as illustrated by the case vignette (Box 1). Where several factors are driving sleep disturbance, solely focusing on one factor is unlikely to lead to satisfactory resolution. Whereas some factors can be readily addressed by intellectual disabilities psychiatry, other factors will require support from sleep medicine specialists and/or primary care. Again, there is a paucity of research in this area.^{Reference Shanahan, Palod, Smith, Fife-Schaw and Mirza9}

For adults with Down's syndrome and OSA, a study provides evidence that the use of continuous positive airway pressure therapy can lead to significant improvements in subjective sleepiness, behaviour and cognitive function.^{Reference Hill, Fairley, Williams, Cooper and Riha41} However, as rightly acknowledged in this study, treatment may be challenging to access and, as previously noted, there may be some patients with intellectual disabilities that struggle to tolerate these investigations and interventions. Such challenges may be overcome by sleep physicians and psychiatrists working collaboratively. For example, our sleep clinic is helping to train intellectual disabilities mental health nurses in exposure therapy to help patients acclimatise to positive airway pressure masks.

Multicomponent cognitive–behavioural therapy for insomnia (CBT-I) is the first-line treatment for chronic insomnia in the general population, and there are aspects of this that can be useful for individuals with intellectual disabilities^31,32 (Table 1). Education on sleep hygiene can be effective in helping the person and carer understand the effects of lifestyle and environment on sleep, for example, caffeine intake, exercise and regular sleep routine, along with lighting, noise and temperature.^{Reference McPherson, Kaushal, Kothapalli and J34} Even modest adaptations to daily routine and the sleeping environment can benefit adults with intellectual disabilities, who are more likely to lack adequate daily exercise and regular exposure to natural light compared with the general population.^{Reference McPherson, Kaushal, Kothapalli and J34} Such advice should be tailored to the needs of the person, for example, interventions to reduce environmental noise for autistic people who are likely to be sensitive to sound.^{Reference McPherson, Kaushal, Kothapalli and J34}

Table 1 Modified CBT-I for adults with intellectual disabilities

The evidence for the pharmacological management of sleep disorders in adults with intellectual disabilities is not well established. The medication which has received the most attention is melatonin, probably because of its favourable side-effect profile, and some studies have shown it to be effective.^{Reference McPherson, Kaushal, Kothapalli and J34} A meta-analysis by Braam et al^{Reference Braam, Smits, Didden, Korzilius, Van Geijlswijk and Curfs43} concluded that in individuals with intellectual disabilities, the use of melatonin decreases sleep latency and the number of wakes per night, and increases the total sleep time. At present, the pharmacological management of non-insomnia disorders tend to follow the same pathways as those for the general population.³¹

Key points

• • Sleep disorders are common in adults with intellectual disabilities.

• • Sleep disorders can adversely affect the overall health and quality of life of adults with intellectual disabilities.

• • Sleep disorders are often treated as a part of a mental disorder rather than specifically screened for and managed.

• • More research into the assessment and management of sleep disorders in adults with intellectual disabilities is required.