Harrison's Internal Medicine Chapter 28. Sleep Disorders Sleep Disorders: Introduction Disturbed sleep is among the most frequent health complaints physicians encounter. More than one-half of adults in the United States experience at least intermittent sleep disturbances. For most, it is an occasional night of poor sleep or daytime sleepiness. However, the Institute of Medicine estimates that 50–70 million Americans suffer from a chronic disorder of sleep and wakefulness, which can lead to serious impairment of daytime functioning. In addition, such problems may contribute to or exacerbate medical or psychiatric conditions. Thirty years ago, many such complaints were treated with hypnotic medications. | Chapter 028. Sleep Disorders Part 1 Harrison s Internal Medicine Chapter 28. Sleep Disorders Sleep Disorders Introduction Disturbed sleep is among the most frequent health complaints physicians encounter. More than one-half of adults in the United States experience at least intermittent sleep disturbances. For most it is an occasional night of poor sleep or daytime sleepiness. However the Institute of Medicine estimates that 50-70 million Americans suffer from a chronic disorder of sleep and wakefulness which can lead to serious impairment of daytime functioning. In addition such problems may contribute to or exacerbate medical or psychiatric conditions. Thirty years ago many such complaints were treated with hypnotic medications without further diagnostic evaluation. Since then a distinct class of sleep and arousal disorders has been identified. Physiology of Sleep and Wakefulness Most adults sleep 7-8 h per night although the timing duration and internal structure of sleep vary among healthy individuals and as a function of age. At the extremes infants and the elderly have frequent interruptions of sleep. In the United States adults of intermediate age tend to have one consolidated sleep episode per day although in some cultures sleep may be divided into a mid-afternoon nap and a shortened night sleep. Two principal systems govern the sleep-wake cycle one actively generates sleep and sleep-related processes and another times sleep within the 24-h day. Either intrinsic abnormalities in these systems or extrinsic disturbances environmental drug- or illness-related can lead to sleep or circadian rhythm disorders. States and Stages of Sleep States and stages of human sleep are defined on the basis of characteristic patterns in the electroencephalogram EEG the electrooculogram EOG a measure of eye-movement activity and the surface electromyogram EMG measured on the chin and neck. The continuous recording of this array of electrophysiologic parameters to define sleep .
