Sleep Disorders


Sleep medicine is an increasingly important specialty as the adverse health consequences of disturbed sleep are recognised by patients and physicians, and the current classification of sleep disorders, as recognised by the American Academy of Sleep Medicine (AASM), is summarised. Two primary sleep disorders, narcolepsy with cataplexy and the disorders of arousal, a symptomatic cluster that includes sleepwalking, confusional arousal and sleep terrors, are reviewed in greater detail. Both disorders can be summarised as being caused by inappropriate switching between the states of vigilance, although they are very different in age of onset, severity and impact on health. In narcolepsy the boundary between sleep and wakefulness is uncontrolled but in the disorders of arousal the boundary between states of sleep is affected. These two disorders also have a genetic predisposition suggesting that advances in knowledge of the relevant mutations could eventually translate into better understanding of the possible mechanisms and hence lead to improved treatments.

Key Concepts:

  • The disorders of sleep are primary, for example as a result of pathology in the mechanisms of sleep and wakefulness, or secondary, for example resulting from a medical condition.

  • Apnoea, interruptions of breathing lasting longer than 10 s that result in arousal from sleep, is the principal presenting condition at sleep clinics.

  • Polysomnography is used to record physiological parameters such as respiration rate, heart rate and blood oxygen level simultaneously with data allowing the stage of sleep or wakefulness to be defined.

  • Basic research into the neurophysiology, molecular genetics and neurochemistry of sleep and wakefulness has been critical for understanding the causes of many sleep disorders.

  • The classification of sleep disorders is continuously evolving and being refined as new disorders are recognised in the clinic and neurophysiological and neurochemical pathologies are better understood.

Keywords: polysomnography; apnoea; rapid eye movement (REM) sleep; non‐rapid eye movement (non‐REM) sleep; parasomnias; electroencephalogram (EEG)

Figure 1.

(a) The computer display during a pediatric polysomnographic recording session showing the electroencephalography channels (upper left panel of the display), muscle activity, electrocardiographic activity and respiratory data including blood oxygen levels (middle left) and concurrent graphical plot of the analysed data including sleep staging and respiratory data (lower left). The right side of the display provides video of the patient and also allows recording of observations from the technician during the recording. All necessary polysomnographic data are therefore displayed and recorded in real time during the session. (b) Polysomnography in progress. Electrodes are positioned on the scalp in standard locations for electroencephalography. Note also the band around the chest, which records the respiratory rate and the sensor for blood oxygen level, which is positioned on the ear lobe. All electrodes and sensors are connected to a pin‐jack panel from which signals are transferred to the amplifier and computer. Courtesy of Grass Technologies, An Astro‐Med Inc. subsidiary.



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Further Reading

American Academy of Sleep Medicine (2005) International Classification of Sleep Disorders: Diagnostic & Coding Manual 2nd edn. Rochester: American Academy of Sleep Medicine.

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How to Cite close
Sinton, Christopher M, and McCarley, Robert W(May 2012) Sleep Disorders. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0001483.pub2]