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.
Disorders of Sleep and Wakefulness
Approach to the Patient: Sleep Disorders
Patients may seek help from a physician because of one of several symptoms: (1) an acute or chronic inability to initiate or maintain sleep adequately at night (insomnia); (2) chronic fatigue, sleepiness, or tiredness during the day; or (3) a behavioral manifestation associated with sleep itself. Complaints of insomnia or excessive daytime sleepiness should be approached as symptoms (much like fever or pain) of underlying disorders.
Persistent psychophysiologic insomnia is a behavioral disorder in which patients are preoccupied with a perceived inability to sleep adequately at night. This sleep disorder begins like any other acute insomnia; however, the poor sleep habits and sleep-related anxiety ("insomnia phobia") persist long after the initial incident. Such patients become hyperaroused by their own efforts to sleep or by the sleep environment, and the insomnia becomes a conditioned or learned response.
Circadian Rhythm Sleep Disorders
A subset of patients presenting with either insomnia or hypersomnia may have a disorder of sleep timing rather than sleep generation. Disorders of sleep timing can be either organic (i.e., due to an intrinsic defect in the circadian pacemaker or its input from entraining stimuli) or environmental (i.e., due to a disruption of exposure to entraining stimuli from the environment). Regardless of etiology, the symptoms reflect the influence of the underlying circadian pacemaker on sleep-wake function.
The history of sleep medicine and sleep research can be
summarized as a history of remarkable progress and, at
the same time, a history of remarkable ignorance. Since
the publication of the second edition in 1999 enormous
progress has been made in all aspects of sleep science
and sleep medicine. I am pleased to see these rapid
advances in sleep medicine and growing awareness about
the importance of sleep and its dysfunction amongst the
public and the profession.
Stages of REM sleep (solid bars), the four stages of NREM sleep, and wakefulness over the course of the entire night for representative young and older adult men. Characteristic features of sleep in older people include reduction of slow-wave sleep, frequent spontaneous awakenings, early sleep onset, and early morning awakening. (From the Division of Sleep Medicine, Brigham and Women's Hospital.)
Physiology of Circadian Rhythmicity
The sleep-wake cycle is the most evident of the many 24-h rhythms in humans. Prominent daily variations also occur in endocrine, thermoregulatory, cardiac, pulmonary, renal, gastrointestinal, and neurobehavioral functions. At the molecular level, endogenous circadian rhythmicity is driven by self-sustaining transcriptional/translational feedback loops (Fig. 28-2). In evaluating a daily variation in humans, it is important to distinguish between those rhythmic components passively evoked by periodic environmental or behavioral changes (e.g.
Evaluation of Insomnia
Insomnia is the complaint of inadequate sleep; it can be classified according to the nature of sleep disruption and the duration of the complaint. Insomnia is subdivided into difficulty falling asleep (sleep onset insomnia), frequent or sustained awakenings (sleep maintenance insomnia), early morning awakenings (sleep offset insomnia), or persistent sleepiness/fatigue despite sleep of adequate duration (nonrestorative sleep). Similarly, the duration of the symptom influences diagnostic and therapeutic considerations.
Restless Legs Syndrome (RLS)
Patients with this sensory-motor disorder report an irresistible urge to move the legs, or sometimes the upper extremities, that is often associated with a creepycrawling or aching dysesthesias deep within the affected limbs. For most patients with RLS, the dysesthesias and restlessness are much worse in the evening or night compared to the daytime and frequently interfere with the ability to fall asleep. The symptoms appear with inactivity and are temporarily relieved by movement.
Specific questioning about the occurrence of sleep episodes during normal waking hours, both intentional and unintentional, is necessary to determine the extent of the adverse effects of sleepiness on a patient's daytime function. Specific areas to be addressed include the occurrence of inadvertent sleep episodes while driving or in other safety-related settings, sleepiness while at work or school (and the relationship of sleepiness to work and school performance), and the effect of sleepiness on social and family life.
The term parasomnia refers to abnormal behaviors or experiences that arise from or occur during sleep. A continuum of parasomnias arise from NREM sleep, from brief confusional arousals to sleepwalking and night terrors. The presenting complaint is usually related to the behavior itself, but the parasomnias can disturb sleep continuity or lead to mild impairments in daytime alertness. Two main parasomnias occur in REM sleep: REM sleep behavior disorder (RBD), which will be described below, and nightmare disorder.
Shift-Work Disorder: Treatment
Caffeine is frequently used to promote wakefulness. However, it cannot forestall sleep indefinitely, and it does not shield users from sleep-related performance lapses. Postural changes, exercise, and strategic placement of nap opportunities can sometimes temporarily reduce the risk of fatigue-related performance lapses. Properly timed exposure to bright light can facilitate rapid adaptation to night-shift work.
While many techniques (e.g.
Behavioral Correlates of Sleep States and Stages
Polysomnographic staging of sleep correlates with behavioral changes during specific states and stages. During the transitional state between wakefulness and sleep (stage 1 sleep), subjects may respond to faint auditory or visual signals without "awakening."
Memory incorporation is inhibited at the onset of NREM stage 1 sleep, which may explain why individuals aroused from that transitional sleep stage frequently deny having been asleep.
Insomnia Associated with Neurologic Disorders
A variety of neurologic diseases result in sleep disruption through both indirect, nonspecific mechanisms (e.g., pain in cervical spondylosis or low back pain) or by impairment of central neural structures involved in the generation and control of sleep itself. For example, dementia from any cause has long been associated with disturbances in the timing of the sleep-wake cycle, often characterized by nocturnal wandering and an exacerbation of symptomatology at night (so-called sundowning).
(BQ) Part 2 book "Sleep medicine - A comprehensive guide to its development, clinical milestones and advances in treatment" presents the following contents: Neurological sleep disorders, psychiatric and psychological sleep disorders, respiratory diseases, medical disorders and sleep, miscellaneous important aspects,...
Treatment is justified if it has significantly improved their wellbeing and function. A combination of medication with psychological techniques is likely to be most beneficial, especially for resistant cases.
Humans spend about a third of the time asleep but why we sleep is not yet fully understood. Sleep is a state of inactivity accompanied by loss of awareness and a markedly reduced responsiveness to environmental stimuli.
From the emergence of clinical sleep medicine marked by the establishment of the
harbinger Stanford Sleep Disorders Clinic in the mid 1970s, offspring sleep disorders
clinics and centers have grown exponentially with the recognition of the unmet
diagnostic and treatment needs of the reservoir of patients suffering from symptoms
of what are now recognized and classified as the nosology of human sleep
Source: Modified from TA Roth, L Merlotti in SA Burton et al (eds), Narcolepsy 3rd International Symposium: Selected Symposium Proceedings, Chicago, Matrix Communications, 1989.
Narcolepsy affects about 1 in 4000 people in the United States and appears to have a genetic basis.
Medical Implications of Circadian Rhythmicity
Prominent circadian variations have been reported in the incidence of acute myocardial infarction, sudden cardiac death, and stroke, the leading causes of death in the United States. Platelet aggregability is increased after arising in the early morning hours, coincident with the peak incidence of these cardiovascular events. A better understanding of the possible role of circadian rhythmicity in the acute destabilization of a chronic condition such as atherosclerotic disease could improve the understanding of the pathophysiology.