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Balk EM, Moorthy D, Obadan NO, et al. Diagnosis and Treatment of Obstructive Sleep Apnea in Adults [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2011 Jul. (Comparative Effectiveness Reviews, No. 32.)
This publication is provided for historical reference only and the information may be out of date.
Obstructive sleep apnea (OSA) is a relatively common disorder in the United States that affects people of all ages, but is most prevalent among the middle-aged and elderly. Affected individuals experience repeated collapse and obstruction of the upper airway during sleep, which results in reduced airflow (hypopnea) or complete airflow cessation (apnea), oxygen desaturation, and arousals from sleep. Hypopneas and apneas are thought to have similar pathophysiologies and bear the same clinical significance, resulting in chronic overnight oxygen desaturation.4
Airway obstruction results in repeated cycles of loud snoring, disruption of rapid eye movement (REM) sleep, and frequent arousals throughout the night followed by hypersomnolence and daytime fatigue serious enough to affect concentration at work and while driving.5 OSA has been associated with a variety of adverse clinical outcomes, such as cardiovascular disease,6–9 including specifically cardiac disease and stroke, hypertension,10–12 and non-insulin-dependent diabetes and other metabolic abnormalities,7,13–16 increased likelihood of motor vehicle and other accidents,17,18 and decreased quality of life.19 These comorbidities combined with the inability to function at a normal level during the day are of considerable clinical concern.
The prevalence of OSA appears to be high, but it is not clear how common the condition is. The Wisconsin Sleep Cohort Study, a prospective natural history study of adults 30–60 years old reported that about 10 percent had clear evidence of OSA in 1988, when the study began.1 The Sleep Heart Health Study, another prospective cohort study, of adults over age 40 years who were not being treated for sleep-disordered breathing, found that about 17 percent had clear evidence of OSA when they were recruited into the study in the late 1990s.2 The National Sleep Foundation poll in 2005 found that as many as one in four American adults are at high risk of OSA and could benefit from an evaluation for OSA.3
OSA is an important public health issue due to associated morbidity and mortality rates; attendant comorbidities, such as hypertension and diabetes; and the adverse effects on daily quality of life. One study of general population volunteers in the U.S. found steadily increasing prevalence from under 10 percent at age 40 to approximately 20 percent among those over 60 years old.20 Evidence also indicates that these rates are rising, most probably due to increasing rates of obesity.21 The prevalence of OSA among those aged 65 and older (Medicare beneficiaries) is believed to be higher. In the population-based Sleep Heart Health Study, the prevalence of an apnea-hypopnea index (AHI; a measure of the presence and severity of OSA) of ≥15 events/hr was 1.7-fold higher in people older than 60 years, compared with people between 40 and 60 years of age.20 Similar observations were made in cohort studies that used population-based samples and a wide range of ages.22–25
Complicating the diagnosis and treatment of OSA is the great degree of clinical uncertainty regarding the condition, due in large part to inconsistencies in its definition. According to a recent technology assessment, controversy regarding which type of sleep monitoring device is most appropriate for diagnosing sleep apnea continues to be ongoing.26 Disagreement also exists about the type and level of respiratory abnormality that should be used to define sleep apnea, particularly for patients who have hypopneic episodes, rather than apnea. Moreover, no current established threshold level for AHI exists that indicates the need for treatment. By consensus, people with relatively few apnea or hypopnea events per hour (often <5 or <15) are not formally diagnosed with OSA. Notably, there is evidence to suggest that patients with relatively mild sleep apnea (fewer apnea-hypopnea events per hour) may have substantially increased cardiovascular disease risk compared with the general population, despite the fact that the AHI values in these patients can be within the range considered normal or only slightly elevated. In addition, the symptom of excessive daytime sleepiness is highly variable and not always present in patients with OSA. In fact, a majority of patients are asymptomatic and may be unaware of the occurrence and frequency of their nocturnal arousals, and, therefore, fail to seek timely medical attention.5 Thus, most patients remain undiagnosed and untreated.5,19,27,28
Given the increasing prevalence of OSA among middle-aged and elderly adults in the U.S., its important effects on mortality and morbidity, and the continued variability in standards used to diagnose and treat the disorder, the present systematic review is timely and may be of potential value in the development of clinical practice guidelines and Medicare coverage decisions regarding OSA.
It should be noted that this report focuses on OSA in adults and does not discuss other sleep apneas, such as central or mixed sleep apnea. Central sleep apnea is associated with conditions caused by damage to the brain stem (such as a stroke or encephalitis), neurological disorders, such as Parkinson’s and Alzheimer’s disease, and congestive heart failure. Patients with central sleep apnea do not have the obstructive characteristics of OSA. Mixed sleep apnea involves events with features of both central and obstructive apneas. Thus symptoms, diagnosis, treatments, and the natural histories of the two types differ, and therefore lie outside the scope of this review.
OSA in children also differs from adult OSA in its etiology, symptomatology, sleep study findings, and consequences. OSA in the pediatric population is largely caused by increased upper airway resistance during sleep due to soft tissue hypertrophy, craniofacial abnormalities, and/or neuromuscular deficits. The general symptoms of OSA in children are similar to that of adults (snoring and excessive daytime sleepiness), but also manifest as hyperactivity, aggressive behavior, poor school performance, and/or morning headaches. While pediatric patients with OSA do have increased risk of hypertension, insulin resistance, and hypercholesterolemia, they do not seem to suffer the same degree of cardiovascular consequences as adults.29 Neurocognitive sequelae, such as poor school performance and attention deficit, are the most obvious consequences. Due to these important differences between adult and pediatric patients this review is restricted to the evaluation and treatment of adult OSA. Thus, this report’s applicability to the pediatric population is uncertain.
Diagnosis
In general, individuals with OSA experience repetitive cycles of upper airway obstruction and frequent nighttime arousals. Upper airway obstruction during sleep is most often due to anatomical anomalies of the nasopharyngeal or mandibular areas that cause narrowing of the respiratory passages, decreased pharyngeal muscle tone that reduces the cross-sectional area of the upper airway, and insufficient neuromuscular responses to airway obstruction.5 This narrowing is often exacerbated by obesity-related peripharyngeal fat.5 AHI, the count of the hourly apnea and hypopnea events during sleep, when combined with determinations of obstruction, is the primary measurement used for the diagnosis of OSA. It (or variations that measure oxygen desaturations or other measures of respiratory disturbance instead of apnea) can by measured by polysomnography (PSG) in a sleep laboratory or by (portable) monitors in other settings. Notably, though, AHI can vary from night-to-night or between settings and does not take into account symptoms, comorbidities, or response to treatment.30
The severity of sleep apnea is typically quantified by the number of apneas and hypopneas per hour of sleep, defined as the AHI, measured during overnight monitoring. The American Academy of Sleep Medicine uses a threshold to define OSA of 15 events/hr (with or without OSA symptoms) or 5 events/hr with OSA symptoms (unintentional sleep episodes during wakefulness; daytime sleepiness; unrefreshing sleep; fatigue; insomnia; waking up breath-holding, gasping, or choking; or the bed partner describing loud snoring, breathing interruptions, or both during the patient’s sleep).31,32 However, as we found during our review, the minimum thresholds to diagnose sleep apnea in research studies vary from 5 to 20 events per hour by PSG.
Polysomnography
The current diagnostic standard used in clinical practice is PSG. The formal diagnosis of sleep apnea requires a comprehensive, technologist-attended sleep study with multichannel PSG performed in specialized sleep laboratories.4,33 Laboratory-based PSG records a variety of neurophysiologic and cardiorespiratory signals that are read by trained technologists and interpreted by sleep physicians after a diagnostic sleep study has been completed. The sleep study incorporates a number of assessments and measurements including: recordings of rapid eye movements, electroencephalogram to detect arousals, chest and abdominal wall monitors to evaluate respiratory movements, electrocardiogram, electromyogram, oximetry, and nasal and oral air flow measurements.5 This process of diagnosing OSA by PSG in a sleep lab has some constraints including cost, inconvenience, and interlaboratory variation in hardware and assessment methods. Additionally, the current clinical standard, which is the 16-channel, in-laboratory PSG has never been validated, and its true sensitivity and specificity in diagnosing OSA is not well documented.26
Portable Monitors
Since in-laboratory PSG is costly, resource-intensive, and potentially inconvenient for the patient, other diagnostic tools have been developed, including portable testing and questionnaires for prescreening patients. Portable monitors vary in the type of neurophysiologic and respiratory information collected, and each synthesizes the accumulated data differently.34 There are different types (classes) of portable monitors. Each gathers different neurophysiologic and respiratory information and may synthesize the accumulated data differently. Portable monitors can be used in the home setting or sleep units.
The American Sleep Disorders Association has classified the different monitors that have been used in sleep studies into four categories, depending on which channels they record and evaluate.34 As we did in the 2007 Technology Assessment of Home Diagnosis of Obstructive Sleep Apnea-Hypopnea Syndrome,26 we used the operational rules described in Table 1 to classify sleep monitors. Briefly:
Table 1
Delineation of operational rules used to classify monitors in sleep studies.
- Type I is facility-based PSG.
- Type II monitors are portable and record the same information as Type I (perhaps with fewer channels). Type II monitors record signals that allow the reliable identification of (micro) arousals from sleep (e.g., electro-oculography, chin electromyography, electroencephalography) and at least two respiratory channels (two airflow channels or one airflow and one effort channel).
- Type III monitors are portable, but do not record the channels that differentiate between sleep and wake, but have at least two respiratory channels (two airflow channels or one airflow and one effort channel).
- Type IV are all other portable monitors that fail to fulfill criteria for Type III monitors. Therefore Type IV channels may include monitors that record more than two bioparameters.
Thus, portable monitors are classified as either Type II, III or IV. Please refer to our previous report for a more complete discussion of portable monitors.26
Pretesting Questionnaires and Other Tests
Questionnaires are used to prescreen patients for further testing or treatment. The most commonly used screening questionnaire in clinical practice is the Epworth Sleepiness Scale (ESS).35 This questionnaire asks patients to rate how likely they are to fall asleep in certain situations, such as riding in the car on a long trip. The ESS focuses solely on sleepiness and not other signs and symptoms of OSA, thus is not specific to OSA. Another questionnaire commonly used in practice is the STOP questionnaire from the University of Toronto.36 In addition, researchers have created models to predict OSA based on demographic features, symptoms, head and neck anatomy, and other variables.
The value of the various questionnaires and other screening tools remains unclear. It is also unknown whether the tests can be accurately used to predict the clinical severity of patients’ sleep apnea and the likelihood of clinically important sequelae. If the screening tests are found to be sufficiently predictive of the results of full sleep testing, the question arises of how best to determine which patients should be prescreened (or sent directly for a sleep study), and, after screening, which should be treated for OSA, tested further, or considered to not have OSA.
Preoperative Testing
The occurrence of both perioperative and postoperative complications in OSA patients has been documented with respect to either surgical intervention for OSA or other procedures.37–39 In a study of patients undergoing hip or knee replacement surgery, 24 percent of 101 patients with OSA had major postoperative complications (respiratory or cardiac) compared with 9 percent of matched controls.39 Other studies have highlighted the risk of anesthesia and analgesia-related adverse outcomes, such as perioperative airway collapse and postoperative oxygen desaturation.37,39 Many surgical patients with OSA, however, remain undiagnosed at the time of surgery,37–39 and may benefit from some type of preoperative assessment for OSA.37 Finding patients with undiagnosed sleep apnea who are undergoing surgery could, in theory, allow for optimization of perioperative care to minimize problems with intubation, extubation, and other respiratory events. At present, the value of screening all or selected surgical patients, and what method of screening would be most effective and efficient, is unclear.
Treatment
Irrespective of the cause of OSA, the defining characteristic is obstruction of the airway during sleep. The most common first line therapy is use of continuous positive airway pressure (CPAP) devices during sleep. However, the machines are not well-tolerated by many patients and may not fully resolve the OSA. Other commonly used treatments include dental and mandibular devices to improve oral airway obstruction, and a range of surgical treatments, including implanted structural supports, to reduce obstruction. Other interventions include devices to alter sleep position, physical therapy to improve oropharyngeal muscle tone, atrial overdrive pacing for patients with nocturnal bradycardia, complementary and alternative medicine, and interventions to achieve weight loss, including bariatric surgery.
Continuous Positive Airway Pressure
CPAP is the standard first-line therapy for most patients diagnosed with OSA.40 The CPAP machine directly relieves the obstruction by counteracting airway narrowing through the delivery of compressed air to the oropharynx, thereby splinting the airway (keeping it open with increased air pressure). When used properly and consistently, CPAP results in improved sleep patterns and quality of life due to decreased daytime somnolence. However, many patients refuse the offer of CPAP therapy, do not tolerate it, or fail to use the portable machine properly.41 These patients remain essentially untreated and receive little or no benefit from the device.
In addition, patients commonly fail to fully comply with CPAP use, either using the device for only part of the night or only on some nights. There are many reasons why patients do not comply with CPAP therapy including, discomfort with the mask or tubing; nasal congestion; poor mask fit with either leakage of air, skin irritation, or claustrophobia; the complexity of the machines, their noise, and the general inconvenience of their use.42,43 Numerous interventions have been proposed to improve compliance with CPAP including training, nursing followup, and ancillary devices to improve comfort. The value of such measures, however, remains unclear.
The issue of adherence to therapy has also resulted in many technological modifications to the machine and the interface (mask) with the goal of improving adherence. Standard CPAP provides continuous fixed pressure during the entire sleep time. Therefore the patient has to both inhale and exhale with the same positive pressure being delivered into the airway. For some patients, especially those with obstructive lung disease, exhaling against this fixed pressure can be quite uncomfortable. One of the first modifications to address this issue was the introduction of bilevel pressure machines. Such devices deliver a higher pressure on inhalation and then a lower pressure during exhalation. A recently introduced flexible bilevel machine allows for a slight reduction in the positive airway pressure at the end of inspiration and at the beginning of expiration. The inspiratory pressure and expiratory pressure changes are determined in part by the patient’s own respiratory efforts. The impetus behind this feature is to promote an increased breathing synchrony with the machine and therefore increase patient comfort. Other CPAP machines have also been designed to improve comfort with the goal of improving compliance. These include C-Flex™ (Respironics, Inc.) where there is a very brief release of the positive airway pressure at the beginning of the expiratory phase of the respiratory cycle, and autotitrating CPAP (autoCPAP) where the machine can sense airflow resistance and increase the positive pressure in response. (Other companies make similar devices, including the Expiratory Pressure Relief™ device by ResMed, Inc., but since we found no eligible studies of other such devices, we do not discuss them further.) The value of the modifications to CPAP, however, remains unclear.
Regardless of the most effective method, improving compliance may require health care resources, and the time and effort of both health care professionals and patients. Thus, it would be helpful if health care providers could determine which patients are at greatest risk of poor compliance and what pretreatment, patient-level characteristics may best predict noncompliance. Efforts to improve compliance could then be focused on those individuals who would most benefit.
Current recommendations for determining the settings for CPAP are for a full night in laboratory CPAP titration.44 The goal of CPAP titration is to obtain the minimal pressure at which all apneas, hypopneas, snoring and arousals from respiratory events in all stages of sleep and in all body positions are eliminated.45 Some patients however undergo a split night study and have both the diagnostic polysomnogram and the CPAP titration done all in one night in the sleep laboratory. The use of a split-night study is meant to reduce wait-time from diagnosis to treatment. However, some studies indicate that split-night CPAP titrations are suboptimal.46
Other methods of determining the optimal CPAP level have been tried with moderate success. In patients with uncomplicated OSA and no significant comorbidities the following methods: a clinical prediction formula, adjusting CPAP for symptoms of snoring, and the use of autoCPAP have all been shown to adequately determine a starting pressure for OSA.47–49 The patients may require an adjustment of the pressure based on symptoms if the optimal pressure is determined with these methods.47 Close followup and monitoring of CPAP pressures is important in all patients regardless of how the CPAP level was determined.
Dental and Mandibular Devices
Oral and mandibular appliances, generally fitted by a dentist, can be worn overnight. Mandibular advancement devices, which are generally worn in the mouth, advance the mandible and usually maintain an opening between the incisors. Other oral devices “retain” or splint the tongue away from the airway, or otherwise mechanically splint the oropharynx and increase upper airway patency during sleep. Current recommendations are to test the oral device for efficacy of treating OSA by either an in-laboratory polysomnogram or home sleep test.50 The American Academy of Sleep Medicine recommends oral appliances for patients with mild to moderate OSA who prefer the oral appliance to CPAP, do not respond to CPAP, cannot have CPAP for various reasons, or who fail CPAP.51
Surgery
For patients with clearly defined anatomic airway obstruction or prior treatment failures with noninvasive techniques (MAD or CPAP), oropharyngeal surgery may be an option. In general, the goal of surgery is to remove the anatomic obstruction and to relieve symptoms. The specific surgery used depends on the patient’s anatomy and the location and cause of the airway obstruction. The most common surgery is uvulopalatopharyngoplasty (UPPP) in which the soft tissue at the back of the throat and uvula (soft palate) are removed to increase width and improve the opening ability of the airway. The tonsils and adenoids may also be removed, if present. Removal techniques used in UPPP include conventional scalpel or laser-assisted procedures. Genioglossal advancement with hyoid myotomy/suspension may also be used to relieve obstruction at the base of the tongue. Another technique, maxillary-mandibular advancement osteotomy, involves moving the jaw forward to enlarge the oropharynx. Recently, radiofrequency ablation, primarily of the base of the tongue and/or nasal turbinates, has also been used to remove or shrink as well as scar redundant tissue to eliminate or otherwise minimize obstruction. Implants that provide structural support to the palate are sometimes also used to improve breathing. All of these surgical interventions may be used alone or in combination, depending on the patient’s anatomy and tolerance for surgery (some procedures require several stages) and the surgeon’s discretion.
Miscellaneous Treatments
Positional therapy involves the use of devices that maintain the patient in a preferred position during sleep. Most prevent the patient from sleeping in a supine position, which in many patients exacerbates airway obstruction. These devices include backpacks or balls strapped to the back. Other devices include wedge pillows to elevate the head and shoulders. Physical therapy of the oropharynx has also been advocated to strengthen the musculature, thus reducing obstruction.
Atrial overdrive pacing is a potential treatment for patients who already have implanted dual-chamber pacemakers. The pacemaker is set to pace the atrium at a rate higher than either the basal atrial rate or the lowest spontaneous rate. This intervention is based on the incidental finding that patients with OSA who received atrial overdrive pacing for atrial tachyarrhythmias reported a reduction in breathing disorders.52 Atrial pacing may maintain sympathetic activity and counteract increases in vagal tone.53
Several pharmacologic agents have been studied for the treatment of OSA. The goals of these agents fall into two categories: ventilatory stimulants or REM sleep suppressants. As an example, selective serotonin reuptake inhibitors may stimulate ventilation and increase upper airway muscle tone. REM suppressant agents theoretically should be effective treatment for patients in whom the majority of the respiratory events occur during REM sleep. Other miscellaneous agents, such as opioid antagonists and nicotine, have also been studied.
Weight Loss
For many patients, obesity is the principle cause of their OSA due to excess fat in the oropharynx and upper airway resulting in poor muscle tone and obstruction. Thus weight loss can be an effective definitive treatment for these patients. The treatments for weight loss in this population are the same as for the general population, including lifestyle changes and bariatric surgery. However, individuals with OSA may be at increased surgical and anesthesia-related risk, due in part to decreased pharyngeal tone and depressed ventilatory responses to hypoxia and hypercapnia.54
Statement of Work
The Medicaid Evidence-based Decisions Project (MED) group, the Medicaid Medical Directors Learning Network, and the American College of Physicians (ACP) requested that the Agency for Healthcare Research and Quality (AHRQ) conduct an assessment of the diagnostic and treatment procedures for OSA. The ACP guidelines committee has expressed an interest in a full review of screening, diagnosis, and treatment of OSA for the purpose of developing a new guideline on the management of the disorder. MED is a collaboration of state Medicaid programs with the goal of making evidence available to states to support benefit design and coverage decisions made by state programs. The present Comparative Effectiveness Review (CER) was requested so that it may be used by the group to support benefit design and state coverage decisions. The AHRQ commissioned the Tufts Evidence-based Practice Center to conduct a CER of studies related to the diagnosis and treatment of OSA.
Three main categories of outcomes of interest in comparative effectiveness research are clinical (or health) outcomes (i.e., events or conditions that the patient can feel, such as disability, quality of life, or death), intermediate or surrogate outcomes (such as laboratory measurements), and adverse events.55 Clinical outcomes relevant to patients with OSA include comorbidities found to be associated with untreated sleep apnea, primarily cardiovascular disease (including congestive heart failure, hypertension, stroke, and myocardial infarction) and non-insulin-dependent diabetes. In addition, mortality due to cardiovascular disease, diabetes, motor vehicle accidents, and other causes represent important adverse outcomes of OSA. Intermediate outcomes of interest in the management of patients with OSA include sleep study measures (e.g., AHI), measures of cardiovascular status (e.g., blood pressure), and measures of diabetes status (e.g., hemoglobin A1c).
All interventions have the potential for adverse events. Therefore, it is important to gather information on both the benefits and harms of interventions in order to fully assess the net comparative benefit. As discussed earlier, compliance with CPAP (or other devices) is an important issue to effectively treat OSA. Interventions that have better compliance or that may improve compliance are clearly of interest. Also of relevance is establishing definitive diagnostic standards and measures that would more clearly identify OSA patients, both symptomatic and asymptomatic. Such standards would serve to markedly reduce OSA-related morbidities as well as related health care costs. Studies have found that prior to diagnosis, OSA patients have higher rates of health care use, more frequent and longer hospital stays, and greater health care costs than after diagnosis.4,39 Therefore, this review is of additional interest to the requesting organizations as well as broadly for the identification of diagnostic tests that would contribute to the early and definitive diagnosis of patients with OSA.
Key Questions
Diagnosis
- How do different available tests compare in their ability to diagnose sleep apnea in adults with symptoms suggestive of disordered sleep? How do these tests compare in different subgroups of patients, based on: race, sex, body mass index, existing non-insulin-dependent diabetes mellitus, existing cardiovascular disease, existing hypertension, clinical symptoms, previous stroke, or airway characteristics?
- How does phased testing (screening tests or battery followed by full test) compare to full testing alone?
- What is the effect of preoperative screening for sleep apnea on surgical outcomes?
- In adults being screened for obstructive sleep apnea, what are the relationships between apnea-hypopnea index or oxygen desaturation index and other patient characteristics with respect to long-term clinical and functional outcomes?
Treatment
- 5.
What is the comparative effect of different treatments for obstructive sleep apnea in adults?
- Does the comparative effect of treatments vary based on presenting patient characteristics, severity of obstructive sleep apnea, or other pretreatment factors? Are any of these characteristics or factors predictive of treatment success?
- Characteristics: Age, sex, race, weight, bed partner, airway, other physical characteristics, and specific comorbidities
- Obstructive sleep apnea severity or characteristics: Baseline questionnaire (and similar tools) results, formal testing results (including hypoxemia levels), baseline quality of life, positional dependency
- Other: specific symptoms
- Does the comparative effect of treatments vary based on the definitions of obstructive sleep apnea used by study investigators?
- 6.
In obstructive sleep apnea patients prescribed nonsurgical treatments, what are the associations of pretreatment patient-level characteristics with treatment compliance?
- 7.
What is the effect of interventions to improve compliance with device use (positive airway pressure, oral appliances, positional therapy) on clinical and intermediate outcomes?
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