Insomnias
Colin A. Espie
Delwyn J. Bartlett
Introduction
Most people’s experiences of poor sleep are memorable, because sleeplessness and its daytime consequences are unpleasant. There are those, however, for whom insomnia is the norm. Persistent and severe sleep disturbance affects at least one in 10 adults and one in five older adults, thus representing a considerable public health concern. Sleep disruption is central to a number of medical and psychiatric disorders, and insomnia is usually treated by general practitioners. Therefore differential diagnosis is important, and respiratory physicians, neurologists, psychiatrists, and clinical psychologists need to be involved. The purpose of this chapter is to summarize current understanding of the insomnias, their appraisal, and treatment. Particular emphasis will be placed upon evidence-based practical management.
Clinical features
Insomnia often remains unreported, and finally presents when a poor sleep pattern is well established. Alcohol has long been a first-line self-administered sleep aid, and recent years have seen an increasing use of ‘over-the-counter’ preparations and ‘self-help’ strategies. The clinical presentation is commonly of a frustrated patient, trapped in a vicious circle of anxiety and poor sleep, who reports having ‘tried everything’.(1,2)
There may be concern about the pattern of sleep. This is the most quantifiable aspect of self-report relating to, for example, length of time taken to fall asleep, frequency and duration of wakenings, or total amount of sleep. A poorly established sleep pattern can lead to unpredictability of what sleep will be like on any given night. Patients often report poor quality of sleep, and subjective perceived quality can be a critically important outcome variable. Typical reports relate to light sleep and sleep felt to be unrestorative. Although it may be unclear how such complaints relate to EEG sleep architecture, the clinician should not overlook qualitative report as it may reflect underlying pathophysiology. Concerns are normally expressed also about the daytime effects of poor sleep. These can be cognitive effects, such as fatigue, sleepiness, inattention, and some impairments in performance, or emotional effects, such as irritability and anxiety.(2)
Classification
The International Classification of Sleep Disorders (second edition: ICSD-2)(3) was published in 2005 and provides the most comprehensive account of sleep disorders, both for descriptive purposes and for differential diagnosis (see Chapter 4.14.1). ICSD-2 describes insomnias as disorders of initiating and maintaining sleep. Patients may have either sleep-onset problems or wakenings from sleep, or both of these. Table 4.14.2.1 summarizes the principal classifications that relate to the insomnias, along with some other sleep disorders where patients commonly present with insomnia symptoms. As can be seen, concomitant symptomatology, potential aetiological factors, and sleeplessness require careful assessment in order to reach a valid diagnosis.
Table 4.14.2.1 The classification and differential diagnosis of the insomnias within ICSD-2 | |||||||||||||||
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Diagnosis and differential diagnosis
Severity of insomnia is judged along dimensions of frequency, intensity, and duration, as well as impact on daytime functioning and quality of life. Generally, the criteria for severe and chronic insomnia are a minimum duration of 6 months with problems presenting three or more nights per week. Restlessness, irritability, anxiety, daytime fatigue, and tiredness commonly accompany such presentations.(2) Mild and moderate insomnia may be diagnosed where problems are less intrusive.
Most patients presenting with insomnia have psychophysiological difficulty initiating and/or maintaining sleep. Usually marked functional effects and somatized tension associated with sleep are evident. The patient reports extreme tiredness while being unable to sleep satisfactorily and appears preoccupied with sleep and its consequences. This contrasts, for example, with the circadian disorders where, in delayed sleep-phase type, the patient may not feel sleepy until late in the normal sleep period, and in advanced sleep-phase type, may waken early and be unable to return to sleep. Taking a history, incorporating screening questions on restlessness, limb movements, and breathing can help to diagnose obstructive sleep apnoea syndrome, periodic limb movement disorder, and restless legs syndrome, although full polysomnographic evaluation may also be required.(4) However, polysomnography is not essential for the diagnosis of insomnia, for which sleep diary monitoring (see Chapter 4.14.1) is usually the most useful form of assessment.(2) Wrist actigraphy is an inexpensive objective evaluation, which estimates sleep/wakefulness based upon body movement.(5) Continuous recordings can be made over 5 to 10 consecutive 24 h periods. It is useful in identifying paradoxical insomnia, and charted data can be inspected for circadian anomalies.
Other causes of insomnia are reported in Table 4.14.2.1 and should not be overlooked. In particular, insomnias due to a drug or substance can include hypnotic-dependent sleep disorder, associated most commonly with benzodiazepine (BZ) drugs where withdrawal leads to exacerbation of the primary problem.(6) This can be mistaken for a severe underlying insomnia and hence reinforce hypnotic dependency. Likewise, a wide range of psychiatric conditions, particularly affective disorders, has associated sleep symptomatology (see Chapter 4.14.1). A primary diagnosis of psychophysiological insomnia cannot be made where diagnostic criteria for DSM-IV Axis I or Axis II disorders are fulfilled. However, it is very important to note that sleep disturbance often precedes depression. The bulk of the psychiatric epidemiological data indicate that insomnia is an independent risk factor for first episode depressive illness, and for recurrence of depression, in adults of all ages.(7,8) Insomnia should not be assumed to be simply a symptom of underlying depression, even when depression is present. Unless the illness courses clearly co-vary it is best to make a diagnosis of co-morbid insomnia. Similar caveats apply to insomnia associated with medical disorders, both in terms of identifying a primary illness, and concluding that insomnia has the status of an associated/ co-morbid disorder (see Chapter 4.14.1).
Epidemiology
Insomnia affects one-third of adults occasionally, and 9 to 12 per cent on a chronic basis. It is more common in women, in shift workers, and in patients with medical and psychiatric disorders. Prevalence amongst older adults has been estimated at up to 25 per cent and sleepiness and hypnotic drugs are risk factors for injury and fracture.(9) The decline in prescription of anxiolytics has been greater than the rate of decline for hypnotics [taking BZ and benzodiazepine receptor agonists (BzRAs) together]. Furthermore, there is increasing use of (off-label) sedative antidepressants primarily to treat insomnia.
Aetiology
Many patients report having been marginal light sleepers before developing insomnia.(4) Sleep disturbance often arises during life change or stress, and such adjustment sleep disorder may represent a normal transient disruption of sleep. However, secondary factors, such as anxiety over sleep and faulty sleep-wake conditioning, may
exacerbate and maintain the insomnia as a chronic problem when sleep itself becomes a focus for concern. People with insomnia may be hyperaroused relative to normal sleepers, for example having higher levels of cortisol and ACTH, and also find it difficult to ‘down-regulate’ their arousal at bedtime.(2,10,11)
exacerbate and maintain the insomnia as a chronic problem when sleep itself becomes a focus for concern. People with insomnia may be hyperaroused relative to normal sleepers, for example having higher levels of cortisol and ACTH, and also find it difficult to ‘down-regulate’ their arousal at bedtime.(2,10,11)
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