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OVERVIEW OF SLEEP DISORDERS Where Does Obstructive Sleep

Apnea Syndrome Fit In?

Jack Coleman, MD

Sleep and wakefulness-the two states of being, the two phases of brain activity that are separate from one another physiologically and psy- chologically, yet wpriek exert tremendous influences on each other.

The awake state and its various disorders have been studied and analyzed for centuries, and all cultures have developed some form of "awake medicine." Between a third and a half of one's life is spent in the sleep state, yet in most cultures it seldom has been addressed beyond the words and writings of the philosophers. Interestingly, more primitive cul- tures seem to pay much more attention to sleep and sleep disturbances, especially dream states, than the more "sophisticated western cultures that generally discussed such notions as quaint superstitions.

Now, in the last half of the 20th century, the importance of sleep and sleep disorders again is realized-perhaps for different reasons than the primitive counterparts. This may be because of the fact that the sleep state itself was able to elude early scientific methods of observation. The subject cannot report sleep experiences the way awake experiences can be re- ported. Observation of many physiologic parameters could not be re- viewed during the sleep stage without disrupting sleep itself until the advent of devices such as the physiographic and electroencephalogram (EEG) recording.

In 1875, Caton discovered EEG waves in dogs? Berger2 described alpha waves from the human brain in 1928, subsequently leading to

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Loomis et al’s7 description of the different stages of sleep based on EEG patterns. In 1953, Aserinsky and Kleitman’ at the University of Chicago described rapid eye movement (REM) sleep. All of this laid the ground- work for the sleep scoring technique of Rechtshaffen and Kales8 based on EEG, electro-oculography (EOG), and electromyography (EMG), which are the standards for sleep scoring. By 1970 sleep researchers at Stanford University routinely began to use respiratory and cardiac measures along with EEG, EOG, and EMG during all night, continuous recordings that were called polysomnography by Holland and co-workers.6

These men laid the foundation for the objective study of sleep and the establishment of sleep disorders medicine. Sleep disorders medicine has been defined by Walsh as ”. . . a clinical specialty which deals with the diagnosis and treatment of patients who complain about disturbed nocturnal sleep, excessive daytime sleepiness, or some other sleep-related pr~blem,”~ and by Dement as ”. . . the branch of medicine that deals with the sleeping brain and all manifestations and pathologies deriving there-

Based upon these definitions and the clinical information generated by various sleep laboratories, a classification of sleep disorders has been established. This effort took 5 years and was a joint effort of the American Sleep Disorders Association (ASDA), European Sleep Research Society (ESRS), Japanese Society of Sleep Research USR), and the Latin American Sleep Society (LASS). The result of this collaboration is The International Classification of Sleep Disorders Diagnostic and Coding Manual, or ICSD.5 This herculean effort was initiated by the Diagnostic Classification Steering Committee of the ASDA, chaired by Michael J. Thorpy, M.D. The ICSD divides 84 sleep disorders into four major categories-dyssomnias, par- asomnias, disorders associated with medical or psychiatric disorders, and proposed sleep disorders (Appendix A).

DYSSOMNIAS

Dyssomnias are sleep disorders that produce either insomnia (diffi- culty initiating or maintaining sleep) or excessive sleepiness. They are the major disorders responsible for disrupted sleep or excessive daytime sleepiness. The dyssomnias are subdivided further into intrinsic, extrinsic, and circadian rhythm sleep disorders.

Intrinsic sleep disorders originate in the body or from causes in the body. External factors may influence these disorders, but are able to do so only because an internal abnormality exists within the body. This includes the insomnias and disorders of excessive sleepiness. The latter includes narcolepsy and the hypersomnias. It also includes the sleep related breath- ing disorders such as obstructive sleep apnea syndrome, central sleep ap- nea syndrome, central alveolar hypoventilation syndrome, and periodic

OVERVIEW OF SLEEP DISORDERS 189

limb movement disorder, all of which can produce symptoms of insomnia or excessive sleepiness.

Extrinsic sleep disorders are those that arise as a result of factors outside the body. Removal or correction of these factors will result in resolution of the sleep disorder. There may be internal factors present that help develop or maimtain the disorder, but these factors alone will not produce a sleep disorder without the external factor being present. This would include those sleep disorders caused by variable or poor sleep habits, disrupting environmental influences (noise, altitude, drugs, aller- gies), ingested chemicals or drugs, and acute stress or conflict.

Circadian rhythm sleep disorders all share a common chronophy- siologic basis. There is an alteration in the timing of the patient’s sleep pattern other than that which is desired or considered normal, and this results in inability to sleep when it is desired, needed, or expected. Intrin- sic, as well as extrinsic, factors may have a major influence on these dis- orders.

PARASOMNIAS

Parasomnias are the results of central nervous activation, usually of the skeletal muscles or autonomic nervous system, resulting in disorders of arousal, partial arousal, and sleep stage transition. The parasomnias occur primarily during sleep, but are not the results of an abnormality of the process of sleep or wakefulness. There are four groups of parasomnias: arousal disorders, sleep-wake transition disorders, parasomnias usually associated with REM sleep, and other parasomnias.

The arousal disorders are disorders of the normal arousal mechanism typically seen in slow-wave sleep. Sleepwalking, sleep terrors, and con- fusional arousals make up the subgroup. Confusional arousals arise typ- ically from arousal from deep sleep in early sleep.

Sleep-wake transition disorders can occur in either direction-sleep to wake or wake to sleep-as well as during transition from one sleep stage to another. Rhythmic movement disorders, sleep talking, and sleep starts or hypnic jerks are the typical disorders seen in this group. Rhythmic movement disorders also can be seen in the awake patient, such as in the mentally retarded. These disorders need not be considered pathologic in many cases.

Parasomnias related to REM sleep include nightmares, REM related sinus arrest, and REM sleep behavior disorder.

Other parasomnias include bruxism and enuresis. Primary snoring also will be found in this category, but not snoring associated with sleep apnea. Also included is sleep related abnormal swallowing syndrome, as well as nocturnal paroxysmal dystonia and neonatal sleep myoclonus. Serious disorders such as sudden infant death syndrome (SIDS), congen-

ital central hypoventilation syndrome, infant sleep related breathing dis- order, and infant sleep apnea are classified in the parasomnias.

MEDICAL OR PSYCHIATRIC SLEEP DISORDERS

This classification is broken down into sleep disorders associated with mental disorders, with neurologic disorders, and with other medical dis- orders. The various disease entities listed under these three subheadings are only those most commonly associated with disorders of sleep and wakefulness, but no attempt was made to compile a complete list of all those medical and psychiatric disorders that have the ability to disrupt sleep and wakefulness.

PROPOSED SLEEP DISORDERS

These disorders are those that are insufficiently or inadequately de- scribed so that their existence as a distinct sleep abnormality can be proven. This may be because of their recently being described (sleep re- lated laryngospasm), too rare to gather enough data on (sleep hyperhid- rosis), difficult to characterize (menstrual-associated sleep disorder), or they are normal variations or extremes (short sleepers and long sleepers).

From these definitions of sleep disorders medicine and from the pre- ceding classifications of sleep disorders, one will see that sleep disorders medicine encompasses a broad array of medical problems. One also could conclude that everyone has, at some time in their lives, suffered from a sleep disorder. If one accepts this premise, then one must ask at what point does a sleep disorder become something to be worried about or become "pathologic"? The reasonable criteria would be that a sleep disorder should be investigated and treated when it: (1) ceases to be a short-term, self-limiting problem and becomes a chronic, nightly problem; (2) when it begins to affect the daytime ability of the patient to function, either subjectively or objectively; (3) when it begins to affect the patient's rela- tionship to others around him or her; (4) when it begins to have a negative affect on pre-existing medical problems; and (5) when new medical prob- lems begin to manifest themselves as a result of the sleep disorder.

References

1. Aserinsky E, Kleitman N: Regularly occurring periods of eye motility and concomitant

2. Berger H: "Uber das Elektroenkephalogramm des Menschen." Arch Psychiatr Nervenber phenomena during sleep. Science 118:273-274,1953

87527-570,1929

OVERVIEW OF SLEEP DISORDERS 191

3. Caton R The electric currents of the brain. BMT 2278,1875 ~~

4. Dement W A personal history of sleep disorders medicine. J Clin Neurophysiol717-47, 19fm _ _ -_

5. Diagnostic Classifications Steering Committee: The International Classifications of Sleep Disorders Diagnostic Coding Manual. Rochester, MN, American Sleep Disorder Associ- ation, 1990

6. Holland V, Dement W, Raymond D: Polysomnography Responding to a Need for Im- proved Communication. Presented at the annual meeting of the Sleep Research Society, Jackson Hole, Wyoming, 1974

7. Loomis A, Harvey E, Hobart G: Cerebral status during sleep as studied by human brain potentials. Journal of Experimental Physiology 21:127-144,1937

8. Rechtschaffen A, Kales A. A Manual of Standardized Terminology, Techniques, and Scor- ing Systems for Sleep Stages of Human Subjects. Los Angeles, CA, UCLA Brain Infor- mation Service/Brain Research Institute, 1968

9. Walsh T: Sleep Disorders Medicine. Rochester, MN, Association of Professional Sleep Societies, 1986

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APPENDIX A

THE INTERNATIONAL CLASSIFICATION OF SLEEP DISORDERS

Dyssomnias Intrinsic sleep disorders

Psychophysiological insomnia Sleep state misperception Idiopathic insomnia Narcolepsy Recurrent hypersomnia Idiopathic hypersomnia Posttraumatic hypersomnia Obstructive sleep apnea syndrome Central sleep apnea syndrome Central alveolar hypoventilation syndrome Periodic limb movement disorder Restless legs syndrome

Inadequate sleep hygiene Environmental sleep disorder Altitude insomnia Adjustment sleep disorder Insufficient sleep syndrome Limit-setting sleep disorder Sleep-onset association disorder Food allergy insomnia Nocturnal eating (drinking) syndrome Hypnotic-dependent sleep disorder Stimulant-dependent sleep disorder

Extrinsic sleep disorders

(continued)

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THE INTERNATIONAL CLASSIFICATION OF SLEEP DISORDERS (Continued)

Dyssomnias (Continued) Alcohol-dependent sleep disorder Toxin-induced sleep disorder

Circadian rhythm sleep disorders Time zone change (jet lag) syndrome Shift work sleep disorder Irregular sleep-wake pattern Delayed sleep phase syndrome Advanced sleep phase syndrome Non-24-hour sleep-wake disorder

Parasomnias Arousal disorders

Confusional arousals Sleepwalking Sleep terrors

Rhythmic movement disorder Sleep starts Sleep talking Nocturnal leg cramps

Nightmares Sleep paralysis Impaired sleep-related penile erections Sleep-related painful erections REM sleep-related sinus arrest REM sleep behavior disorder

Other parasomnias Sleep bruxism Sleep enuresis Sleep-related abnormal swallowing syndrome Nocturnal paroxysmal dystonia Sudden unexplained nocturnal death syndrome Primary snoring Infant sleep apnea Congenital central hypoventilation syndrome Sudden infant death syndrome Benign neonatal sleep myoclonus

Sleep-wake transition disorders

Parasomnias usually associated with REM sleep

Sleep disorders associated with medicaVpsychiatric disorders Associated with mental disorders

Pyschoses Mood disorders Anxiety disorders Panic disorders Alcoholism

Cerebral degenerative disorders Dementia Parkinsonism Fatal familial insomnia Sleep-related epilepsy Electrical status epilepticus of sleep Sleep-rela ted headaches

Associated with other medical disorders Sleeping sickness Nocturnal cardiac ischemia

Associated with neurological disorders

(continued)

OVERVIEW OF SLEEP DISORDERS 193

THE INTERNATIONAL CLASSIFICATION OF SLEEP DISORDERS (Continued) -

Sleep disorders associated with medicaWpsychiatric disorders (Continued) Chronic obstructive pulmonary disease Sleep-related asthma Sleep-related gastroesophageal reflux Peptic ulcer disease Fibrositis syndrome

Proposed sleep disorders Short sleeper Long sleeper Subwakefulness syndrome Fragmentary myoclonus Sleep hyperhidrosis Menstrual-associated sleep disorder Pregnancy-associated sleep disorder Terrifying hypnagogic hallucinations Sleep-related neurogenic tachypnea Sleep-related laryngospasm Sleep choking syndrome

From Diagnostic Classifications Steering Committee: The International Classifications of Sleep Dis- orders Diagnostic Coding Manual. Rochester, MN, American Sleep Disorder Association, 1990; with per- mission.