Dr. Quan is director of the Sleep Disorders Center, associate director of the Arizona Respiratory Center, and professor of medicine and anesthesiology at the University of Arizona College of Medicine in Tucson. Reprinted from TEN. 2001;3(9):39-42.



Sleep is a required biological function that outwardly appears to be a simple process, but is in actuality quite complex. There are over 80 recognized conditions that can affect sleep and waking behavior. The most common is insomnia, which affects up to 30% of the general population. However, obstructive sleep apnea is the sleep disorder that usually prompts a patient’s referral to a sleep disorders center. These centers offer comprehensive evaluation and treatment in a single location. Accreditation by the American Academy of Sleep Medicine offers assurance that certain standards related to medical care, facilities, equipment, and technician staffing have been met. Polysomnography, the most common sleep laboratory procedure, is usually performed to determine if a person has obstructive sleep apnea. Although evaluation and treatment in a sleep disorders center are expensive, most insurance carriers provide reimbursement for polysomnography. Sleep disorders centers are costly to develop and maintain, but can be economically viable and beneficial to patients.



Sleep, as defined by The American Heritage Dictionary,1 is “a natural, periodically recurring physiologic state of rest, characterized by relative physical and nervous inactivity, unconsciousness, and lessened responsiveness to external stimuli.” This relatively simple definition belies the complexity of a physiologic function that occupies approximately one third of our time. Far from being a homogeneous state, a night of sleep generally consists of four sequential units containing episodes of nonrapid eye movement (NREM) and rapid eye movement (REM) sleep (Figure). During polysomnography (simultaneous monitoring of several physiologic parameters during sleep), REM sleep is distinguished from NREM sleep by rapid movements of the eyes. Awakening from REM sleep is associated with dream recall. Although most metabolic functions decline with onset of sleep, there is a paradoxic increase in these activities during REM sleep.


Sleep, by its very nature, is tightly intertwined with wakefulness. Alterations in sleep affect wakefulness and vice versa. Although the requirement for sleep is a biologic imperative, the purpose of it remains unknown.2 Some propose that the function of sleep is restorative. During sleep, there is active synthesis of proteins, which is important for regeneration of stores depleted during wakefulness. Others suggest an ethological or conservation theory: Because we live in an environment with periodic cycles of changing light and temperature, species survival would be enhanced if our activity cycle were synchronized to these cycles.

Most adults require 7–8 hours of sleep per night. However, many individuals can function well with less than this amount, and others require more. Nevertheless, as one becomes increasingly sleep deprived, the biological urge to sleep becomes more irresistible.

Epidemiology of Sleep Disorders

Given the complexity of sleep, it is not surprising that symptoms of poor sleep or excessive daytime sleepiness are widespread. In surveys of the adult general population, the prevalence rate of insomnia complaints ranges from 17.4% to 37.8%, with higher levels in women and the elderly.3 Excessive daytime sleepiness is common as well, with rates ranging from 4% to 12%, and higher percentages in older individuals.4,5 In addition to female gender and advancing age, other commonly reported risk factors for poor sleep include snoring and chronic medical and mental health problems.3 Sleep problems are not limited to adults. One recent study in children 3–14 years of age found insomnia in 16.8% and excessive daytime sleepiness in 4.0%.6

Types of Sleep Disorders

In its diagnostic and coding manual, the American Academy of Sleep Medicine lists over 80 disorders of sleep and waking behavior.7 Most of these adversely impact individual quality of life. Some are potentially life-threatening to the affected individual and can endanger public safety by causing motor vehicle or industrial accidents.

The most common sleep disorder is insomnia: Over 30% of American adults may be affected. Insomnia refers to trouble initiating or maintaining sleep. Insomnia can develop as a result of a number of medical, social, or environmental factors. Many occurrences are transient and directly attributable to an obvious cause. In some chronic cases, however, there does not appear to be any apparent predisposing factor. In these situations, the condition is classified as psychophysiologic insomnia.

In addition to sleep impairment, insomnia may produce significant problems with daytime functioning. Insomniacs have greater difficulty with concentration and coping with minor problems; they also have more motor vehicle accidents.8 Although many self-medicate with over-the-counter or complementary and alternative medications, most insomniacs do not seek medical treatment from their physicians.9

Although insomnia is the most prevalent sleep disorder, obstructive sleep apnea (OSA) is the one that most commonly results in a medical evaluation. OSA is characterized by apnea, or cessation of breathing, during sleep. The oropharyngeal structures collapse during inspiration, resulting in an obstructed airway. In addition to having such episodes witnessed by a bed partner, loud snoring and excessive daytime sleepiness are the other prominent symptoms. OSA occurs frequently: The estimated prevalence is 4% in middle-aged men and 2% in middle-aged women, with higher rates in the elderly.10 Children can also have OSA and it can contribute to poor school performance and hyperactivity.11,12 The excessive daytime sleepiness associated with OSA may be quite severe and as a result, individuals with OSA have a high rate of motor vehicle accidents.13 Studies have linked OSA as a causal factor in the development of hypertension, coronary heart disease, and stroke.14-16

Given that the prevalence of coronary heart disease is ~5% and that sleep disorders adversely impact quality of life and mortality, identification and treatment of sleep disturbances should be an important public health mandate. Unfortunately, this is not the case. It was not until 1992 that the National Commission on Sleep Disorders Research highlighted the inadequacy of patient and professional education and research in sleep in the United States. This led to the creation of the National Center on Sleep Disorders Research within the National Institutes of Health, with a mandate to conduct and support research and educational activities related to sleep disorders. Nevertheless, because recognition and treatment of sleep disorders by primary care providers remains deficient, thus, sleep disorders centers play an important role in the delivery of health care.

Historical Evolution and Function of Sleep Disorders Centers

Sleep disorders centers provide a centralized location where patients with sleep problems can receive comprehensive evaluation and treatment. The concept of the sleep disorder center developed from the visionary leadership of Dr. William Dement at Stanford University, who along with several other clinicians and sleep investigators, founded the Association of Sleep Disorders Centers (ASDC) in 1975.17 These pioneers thought that diagnosis and treatment of sleep disorders should be performed at a central location where there was specific expertise and interest. The nascent ASDC sparked further interest and publicity in sleep disorders, resulting in an exponential growth in the number of sleep disorders centers. They are now found not only in academic medical centers, but also in community hospitals in both large- and medium-sized population centers.

All sleep disorders centers provide comprehensive evaluation and treatment services for the entire spectrum of sleep disorders. However, the most common problem evaluated at most centers is OSA.18 This represents an evolution from 20 years ago when the number of centers was much smaller and the diversity of patients evaluated was greater.19

Generally, an evaluation begins with a history and physical examination obtained by a sleep specialist in a clinic or office setting. For some sleep problems, such as restless legs syndrome, the history and physical examination may be sufficiently diagnostic so that no further extensive testing is required and treatment can be started. In many other cases, additional diagnostic tests are needed. Questionnaires that help evaluate the patient’s degree of sleepiness or assess the presence of depression, and sleep logs, which provide an indicator of a patient’s sleep pattern, are often used. Polysomnography is the diagnostic test used most often.

Polysomnography is performed in the sleep laboratory of sleep disorders centers. Patients are asked to sleep in the laboratory during their normal sleep time and simultaneous recordings of electroencephalogram, electrooculogram, chin electromyogram, electrocardiogram, leg electromyogram, ventilatory function, and oxygen saturation are obtained. Originally, these parameters were recorded simultaneously on an analog chart recorder. However, most laboratories now use computerized digital acquisition systems for both display and data processing.

Polysomnography is usually performed when the diagnosis of sleep apnea is being considered, but it also provides useful information in the evaluation of other sleep disorders. It is often performed when nasal continuous positive airway pressure (CPAP) is being titrated to treat sleep apnea. In CPAP, above-ambient airway pressure is applied using a nasal mask. This produces pneumatic splinting of the upper airway and prevents obstruction. The amount of pressure required varies from patient to patient. Therefore, it is current clinical practice to increase the level of CPAP until sleep disruption, snoring, and apneic events are abolished. This requires concurrent polysomnography.

Two other tests commonly performed in sleep laboratories are the Multiple Sleep Latency Test and the Maintenance of Wakefulness Test. Both provide an objective measure of sleepiness. The Multiple Sleep Latency Test consists of four or five sessions during the day, each separated by 2 hours, during which the patient is asked to fall asleep with electroencephalographic, electrooculographic, and chin electromyographic monitoring. The average time taken to fall asleep is the mean sleep latency and an objective index of daytime sleepiness. The structure of the Maintenance of Wakefulness Test is similar to the Multiple Sleep Latency Test, but patient is asked to stay awake instead of to fall asleep. Thus, the Maintenance of Wakefulness Test provides a measure of daytime vigilance.

After all diagnostic testing is completed, sleep disorders centers provide a diagnostic impression and recommendations for therapy. Therapeutic interventions may include medication, behavioral strategies, oral appliances, and nasal CPAP. Although all sleep disorders centers have the capability to provide treatment and follow-up, insurance contracts and long-distance travel for patients often dictate that therapeutic regimens be initiated by the patient’s primary care provider.

Most sleep disorders centers provide comprehensive evaluation and treatment for all sleep problems. Some, however, only evaluate and treat a narrow spectrum of sleep problems—most commonly, sleep-disordered breathing or sleep apnea. Still others focus on pediatric sleep disorders.

Many sleep disorders centers, especially those affiliated with an academic healthcare system, are actively engaged in clinical research. Pharmaceutical companies sponsor a large proportion of this research, which usually involves clinical testing of new therapeutic compounds for various sleep disorders. Often, patients evaluated at these sleep disorders centers are offered the opportunity to participate in clinical trials. Some centers are also involved in research funded by federal agencies such as the National Institutes of Health and the Department of Defense. These projects are usually more focused on the pathophysiology of various sleep disorders.

Accreditation and Organizational Structure of Sleep Disorders Centers

The American Academy of Sleep Medicine (www.aasmnet.org), which is the successor to the ASDC and the principal professional society representing sleep clinicians and researchers, accredits sleep disorders centers and specialty laboratories meeting its standards.2 These standards represent what the academy believes are the minimum required for quality care in the evaluation and treatment of sleep disorders. The standards contain requirements for facilities, equipment, and technician staffing. A major requirement is that each center must have a diplomat of the American Board of Sleep Medicine (www.absm.org) on staff, to insure that the center’s clinical evaluations occur under a sleep medicine specialist’s general oversight.

Sleep disorders centers and specialty laboratories may voluntarily apply for accreditation. After an application fee, the accreditation process involves review of the center’s materials, to see how the center or laboratory meets the academy’s standards, and a site visit by a team of sleep specialists. The duration of accreditation is for 5 years, after which reaccreditation is required. While there are currently over 400 centers and laboratories accredited by the American Academy of Sleep Medicine, there are many unaccredited facilities. Some of these facilities function very similarly to accredited centers, while others are sleep centers in name only, providing laboratory testing with varying degrees of supervision by sleep medicine professionals. In these facilities, the sleep specialist generally does not see the patient prior to testing and treatment is not provided.

The physical facility for a sleep center must provide an area where patients can be interviewed and examined by a clinician, and a sleep laboratory where polysomnography can be performed. In some small facilities, the bedrooms function as examination rooms during the daytime. In others, patients are interviewed in clinics or offices separate from the sleep laboratory. Most sleep centers have at least two bedrooms, and some have four or more. There should be a sufficient number of technologists to perform the polysomnograms. The American Academy of Sleep Medicine recommends a ratio of no more than two patients to one polysomnographic technologist.20 Most centers employ at least one technologist who has passed the registry examination administered by the Board of Registered Polysomnographic Technologists (www.brpt.org).

Sleep Center Economics

The costs of developing and running even a small sleep disorders center can be substantial. The first requirement is a location with adequate space for the sleep laboratory. Many centers are “free standing,” ie, not located within a medical center, and rent payments can be substantial. Second, the monitoring equipment is a significant capital expense. The cost to equip a center with two bedrooms may approach $100,000 if the newest technology is purchased. Third, there are personnel costs. Polysomnographic technologists earn $25,000–$45,000 per year, depending on the location. In addition, there are costs for secretarial/reception and billing services. For institutions that lack the expertise to develop or run their own center, consulting firms can be contracted to assist in development and maintenance. In addition, there are companies specializing in sleep laboratory management.

Despite the high initial start-up costs and the ongoing expenses of managing a sleep center, the number of both accredited and unaccredited facilities has been growing. This growth has been fueled by a demand for services and by insurance carriers’ recognition that evaluation and treatment of sleep disorders are medically indicated and reimbursable. Medicare covers polysomnography for the diagnosis of sleep apnea, narcolepsy, parasomnias, and male impotence, but not for insomnia. Billing for sleep center physician professional charges related to outpatient visits is accomplished using standard Current  Procedural Terminology evaluation and management codes. Fees for polysomnography, MSLT, and MWT testing are billed as outpatient procedures even though patients spend the night in the laboratory. Some centers, particularly free-standing ones, bill a global fee that encompasses both the technical expense of performing the procedure and a professional interpretation. Physicians interpreting the studies are then paid by the center on a contractual basis. Other centers bill only a technical fee and the physician bills for the interpretation separately.

The total fees charged for sleep laboratory procedures vary from one facility to the next, depending on the area of the country, operational expenses, collection rates, and type of facility (free-standing versus hospital-based). Global fees generally cost $1,100–$2,000. Insurance reimbursement is highly variable, but generally ranges from 50% to 80% for most commercial carriers. The current Medicare relative value units for sleep laboratory procedures are shown in the accompanying Table. Insurance companies often calculate their reimbursement rates as a percentage of the Medicare allowable. Many health maintenance organizations and preferred provider organizations contract with only certain sleep centers at substantial discounts. Some insurance carriers also distinguish between accredited and unaccredited sleep centers, allowing reimbursement only for those accredited by the American Academy of Sleep Medicine.



There is increasing recognition on the part of the public and the medical community that sleep disorders are common and that they represent a largely unmet public health need. As comprehensive diagnostic and treatment facilities, sleep disorders centers are filling this void. Under our current pluralistic healthcare system, they are both economically viable and contribute to better health care for many Americans.  PP


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