When to Order a Sleep Study and How to Read the Report — Part I
Authors: Donna Arand, PhD, Kettering Medical Center, Wallace Kettering Neuroscience Institute; George Burton, MD, Kettering Medical Center, Wallace Kettering Neuroscience Institute, Wright State University; and Michael Bonnet, PhD, Kettering Medical Center, Wallace Kettering Neuroscience Institute, Dayton Department of Veterans Affairs Medical Center, and Wright State University.
Editor’s Note—Sleep disorders are extremely common and the primary care physician (PCP) can play an important role in their identification and management. It is estimated that half of the population has some problem with sleep, especially the most common complaints of insomnia and daytime sleepiness.1 Sleep disorders affect both the individual and society, costing $275 million dollars per year in direct costs and more than $43 billion dollars per year for sleepiness-related accidents.2 The indirect cost of lost productivity is incalculable. The PCP is the first line of defense for identifying patients with sleep disorders and initiating appropriate evaluation and managing long-term treatment.
Causes of sleep complaints are quite varied and include both physiological and behavioral components. Physiological causes typically require a sleep laboratory evaluation for diagnosis. It is important for the PCP to know when to order a sleep study and also how to understand and evaluate the study results. Sleep study data provide an array of quantitative information that can be extremely informative when viewed in the context of the patient’s sleep and medical history. The PCP has the most knowledge about the patient’s medical, social and psychiatric history and can therefore be essential to the clinical application of the sleep study findings. He or she can help identify secondary problems and help with initiating and managing treatment.
Physiological causes of sleep disorders are well known and the effect of behavioral causes of sleepiness has recently become evident. Catastrophic events, including the grounding of the Exxon Valdez, the explosion of the space shuttle Challenger, and the nuclear disaster at Three Mile Island, have been linked to excessive operator sleepiness from sleep deprivation. Our new technologies have provided a "24/7" world where sleep is sacrificed to stay engaged around the clock to meet increasing needs and demands. Currently, surveys show an increasingly sleepy population that have ignored their sleep needs and created a "national sleep debt." Evaluation of this epidemic of sleepiness does not necessarily require laboratory study, but rather mandates identification of the cause of the sleep debt and clear communication of effects and treatment. The PCP is in a unique position to identify and manage our national sleep debt.
This overview will initially identify the components of a sleep history that are important in the diagnosis of common sleep disorders and determine whether sleep laboratory testing is needed. Part II of this manuscript will explain the basic data found in a sleep study report to enable the ordering physician to understand and interpret the results. Finally, common sleep disorders encountered in primary practice will be discussed along with the current understanding of causes and treatment options.
Prevalence of Sleep Disorders
It is estimated that half of the population have problems with their sleep.1 Insomnia is an occasional problem for 30-35% of the population and a severe or chronic problem for 10-15% of the population.3-6 In spite of the significance and prevalence of this disorder, only 1 in 4 patients mention the problem to a physician, generally in the course of a visit for another primary problem.3 Similarly, excessive sleepiness during wakefulness affects up to 5% of the population.4 However, some patients may be reluctant to mention a sleep problem unless specifically questioned by their physician.
Classification of Sleep Disorders
Sleep disorders include complaints about excessive sleepiness, insomnia, circadian rhythms, and parasomnias. Categorization of disorders by complaint has recently been abandoned in recognition of the fact that sleep is part of a 24-hour sleep wake cycle and behaviors during each state influence the other. Consequently, the inability to fall asleep or stay asleep (insomnia) may cause sleepiness during the wake period, while a circadian shift may appear to be a problem with insomnia at night and sleepiness during the day. Depending on which aspect of the problem the patient reported, the complaint of insomnia or excessive sleepiness could represent the same underlying disorder!
The current International Classification of Sleep Disorders divides sleep disorders into dyssomnias and parasomnias and lists 54 individual sleep disorders.7 (See Table 1.)
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Dyssomnias are divided into intrinsic, extrinsic, and circadian rhythm disorders. Parasomnias are divided into 3 classes based on the origination of behavior in relation to their sleep-related trigger. The current terminology takes into account that sleep and wake periods may be reversed in a "24/7" world, so it can no longer be assumed that a person’s sleep period is at night or that work occurs during the daytime (eg, shift workers).
Because of this, reference is made to wake functioning instead of daytime functioning. Where reasonable, this has also been reflected in current diagnostic terminology such as "sleep terrors" rather than "night terrors" and "sleep epilepsy" rather than "nocturnal epilepsy."
Familiarity with the nosology is useful for understanding the various factors that can contribute to sleep problems. Once the disorders or symptoms of a disorder are identified, treatment or the need for sleep testing becomes apparent.
Diagnosing Sleep Disorders
The majority of the sleep disorders are diagnosed from a sleep history and do not require a sleep study, called a polysomnogram (PSG). A sleep history reveals some diagnoses that cannot be made through testing, as well as symptoms of physiological problems that need to be evaluated by a sleep study.
Many sleep patients have more than one sleep diagnosis, especially when study results are combined with information from the sleep history. For example, a patient may be given diagnoses of obstructive sleep apnea, periodic limb movements, and insufficient sleep. Missing diagnoses may result in protracted reassessment for sleep complaints that have improved but have not been adequately resolved following treatment of a single disorder. Identifying all problems at the outset will result in a comprehensive management plan and avoid delays in effective treatment.
Sleep History and Physical Examination
Sleep History
Sleep patterns change as we grow older, and it is important to determine when the current sleep problem began (circumstances surrounding the onset) and how it has progressed. Sleep is also part of a 24-hour circadian rhythm in which the amount and quality of the sleep period affects wake functioning, and wake behaviors affect sleep quantity and quality. A sleep history, therefore, must include descriptions of sleep habits, behaviors, and medication use, as well as waking function.
Often patients are unaware of their sleep behaviors, so a bed partner is an excellent source of information. An adequate sleep history and physical examination obtained prior to a patient’s referral to a sleep disorders center may obviate the need for a more in-depth sleep physician consultation.
Sleep Schedule Habits
A patient’s sleep schedule includes information about bedtime, time to fall asleep, wake times, and any periods of napping. This is often documented with a sleep log from a 2-week period. (See Figure 1.) The sleep log may reveal circadian problems and sleep deprivation issues, as well as some sleep hygiene problems. If the sleep log shows a stable shift of the sleep period to the early morning hours, a delay in the sleep phase has been established. For example, falling asleep too early, as is common in the elderly, is called advanced sleep phase. These circadian problems may present as insomnia and daytime sleepiness. These disorders do not require a PSG and they only need to be treated if the patient is unable to function on this schedule or is unhappy with it. Treatment of phase shift disorders involves chronotherapy, bright light therapy, or physical activity, and can be used individually or in combination. Chronotherapy involves delaying bedtime by an additional 3 hours per day until the desired bedtime is reached. Bright light and physical activity are used to anchor the desired wake time. Also, even though it is not FDA approved, melatonin has some efficacy in circadian rhythm problems.
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A periodically changing sleep pattern occurs with shift workers. More than 20% of the US population is involved in shift work.8 Shift workers have more absenteeism, health problems, and family and social problems. Specific problems for female shift workers include increased risks of spontaneous abortions, menstrual abnormalities, and breast cancer. Rotating shift workers have the most debilitating schedules and often develop difficulty in sleeping or functioning most of the time due to chronically changing sleep/wake rhythms (shift work sleep disorder). Moving the work shift forward 8 hours every 2 weeks or longer is the least disruptive.
A very irregular sleep pattern is suggestive of inadequate sleep hygiene. This is characterized by fragmented sleep during the major sleep period and napping during the primary wake period. The fragmented sleep period is typically reinforced with inappropriate activities during the wake episodes such as eating, watching TV, or other distracting activities. The absence of a clear pattern of sleep and wake will flatten circadian rhythms and will result in decreased differentiation between states of sleepiness and alertness. Treatment involves establishing regular sleep times, avoiding naps, caffeine, alcohol, and stimulants.
Sleep logs can also identify short sleepers, long sleepers, and individuals with non-24 hour rhythms. A range of 4-10 hours of sleep is considered the normal range of sleep time. Some individuals also have sleep-wake cycles longer or shorter than 24 hours and may have difficulty setting regular sleep times. In general, sleep times are adequate in these cases, but either waking adaptation must occur or strict adherence to a sleep and wake schedule must be enforced.
The total daily sleep time is very important information for evaluating any sleep complaint and it can also be calculated from the sleep log. The majority of adults sleep 7 hours or less during the week. On the weekends, 25% of adults sleep 9 hours or more.9 Adults average about 8.5 hours per night if undisturbed. The use of an alarm clock or other external stimuli to awaken means that some partial sleep deprivation has occurred. This is usually associated with a pattern of shortened sleep time on workdays and "sleeping-in" on days off work. This volitional behavior is the hallmark of insufficient sleep syndrome and is the most common cause of excessive sleepiness.10 The effects of chronic partial sleep deprivation are significant. Insufficient sleep often co-exists with other sleep disorders, yet is often overlooked and contributes to sleepiness after other disorders are treated. Another study, which highlights this sleep controversy, has suggested that sleeping more than 8 hours is associated with increased mortality.11
Sleep Environment
The bedroom should be conducive to sleep, otherwise sleep may be disrupted and sleep time reduced. Noise, odors, a snoring bed partner, light and extremes of temperature all will disrupt sleep. Additionally, allowing pets in bed will result in more sleep disruption. Environmental sleep disorders are easily identified from the history, but effective solutions may not be simple or acceptable to the patient. Characteristically, patients whose sleep disorder is related to their surroundings will sleep better in unfamiliar surroundings, such as the sleep laboratory.
Activities in the Bedroom
Volitional behaviors that occur in the bed or bedroom can have a significant effect on sleep. Engaging in stressful or stimulating activities such as watching television, talking on the phone, exercising, or working in the bedroom near bedtime, can result in stimulation rather than relaxation and drowsiness in bed. These behaviors are part of inadequate sleep hygiene and can result in insomnia. The bedroom should only be used for sleep and sex.
Sleep-Related Behaviors
Behaviors that occur during sleep are often unknown to the sleeping patient unless reported by others. A sleep partner is a valuable source of knowledge concerning a patient’s sleep behaviors. Common behaviors include snoring, pauses in breathing, and jerking of the legs or arms. These are symptoms of the most common physiological disorders, sleep apnea and periodic limb movements. They require sleep studies for quantification and diagnosis. Other behaviors such as sleep talking, sleepwalking, and bruxism are parasomnias that do not typically require sleep studies unless epilepsy is suspected or co-existent physiological disorders such as sleep apnea exist. Knowing when the parasomnia occurs during the night is useful for diagnostic purposes as some are tied to sleep stages that occur primarily during certain portions of the sleep period.
Some symptoms experienced by the patient at the onset and termination of sleep are characteristic or diagnostic of some sleep disorders, but the symptoms may seem so unusual or unrelated to the primary sleep complaint that the patient does not spontaneously report them. Symptoms of narcolepsy including sleep paralysis, cataplexy, and hypnogogic/hypnopompic hallucinations need to be specifically queried. The unpleasant sensations of restless legs often described as creepy, crawling, or tingling sensations occurring at rest and requiring vigorous movement to dissipate should be specifically addressed. Sleep testing is indicated to aid in the diagnosis of narcolepsy; however, the diagnosis of restless legs is entirely made from the history.
Wake Time Functioning
Sleep problems can significantly impair the patient’s ability to function during wake, and evaluation of general wake functioning is a useful reflection of the severity of the sleep problem. Memory, concentration, mood, and performance of routine daily activities are commonly affected. Falling asleep driving, at work, and in most sedentary situations destroys the quality of life and endangers lives. The greater the impairment and the more hazardous the activities, the more urgent is the need for diagnosis and treatment. Caution or restrictions about driving or the operation of machinery may be necessary until effective treatment is initiated. If sleep time is adequate, the threshold for PSG evaluation in a sleepy person should be low.
Wake Time Activities
Daily physical activity is beneficial to sleep if done in the late afternoon, but not within a few hours of bedtime. Exercise done within a few hours of going to sleep can have an arousing effect, which may delay sleep onset and contribute to a complaint of sleep onset insomnia. Exercise in the morning has minimal effect on sleep. Exercise done in the late afternoon can improve sleep. This is certainly conventional wisdom. However, there are little data to support it. Exercise at any time probably has a salutary effect on sleep.
Napping during the typical wake period can reduce and fragment sleep during the primary sleep period and should be avoided in patients with this complaint. However, for some individuals, napping is necessary due to age (children and elderly) or other medical conditions. For these patients, the timing and length of naps are important. Naps can result in sleep onset insomnia if they occur too close to the primary sleep period and they can fragment or shorten the major sleep period if they are lengthy. Naps of an hour or less are probably beneficial, particularly in the elderly.
Social History
Caffeine, nicotine, alcohol, and recreational drugs are substances that affect sleep. Caffeine is found in chocolate and cola, as well as tea and coffee. Sensitivity to caffeine varies and its stimulant properties can delay sleep onset and contribute to fragmented sleep.12 Less pronounced effects can be caused by nicotine. The effects of alcohol include initial relaxation and sleepiness followed by arousal and increased wake about 4 hours later after the alcohol is consumed and metabolized. Alcohol reduces sleep latency and suppresses rapid eye movement (REM) sleep in the first half of the night. In the second half of the night there is sleep fragmentation and REM-rebound. The REM-rebound may give rise to disturbing dreams. These effects are dose-related and accounted for by the half-life for metabolism. At low doses (0.16g/kg), there is a reduced sleep latency and increased or unchanged sleep time, although sleep stage effects maybe present.13 The mechanisms for CNS effects of low amounts of alcohol are GABA facilitation and glutamate inhibition. Tolerance to the sedative and sleep-stage effects occurs within 3 nights of repeated administration.14 Alcohol withdrawal may increase sleep latency, and the patient may interpret this as a need for a "nightcap," resulting in an alcohol-dependent sleep disorder. Long-term use of excessive alcohol can result in long sleep latencies and light and fragmented sleep years after termination of drinking.
Medications
Many medications with effects on the CNS can produce sleepiness or sleeplessness as a side effect. The effect is usually dose dependent so by decreasing the dosage it may be possible to produce both a therapeutic effect and minimize the sleep disturbance. Sleeplessness can occur with some antihypertensives, decongestants, corticosteroids, and antidepressants, particularly MAO inhibitors as well as some selective serotonin reuptake inhibitors.15 Lipophilic beta blockers are most active in the CNS; these include propranolol and pindolol, which have the greatest propensity to cause sleep disruption.16
Sleep or waking functioning may become impossible without the stimulant or hypnotic medication as in the case of stimulant-dependant sleep disorder, hypnotic-dependent sleep disorder, and alcohol-dependent sleep disorder. The use of multiple stimulant/sedating agents is not unusual and effects are complicated by development of tolerance, withdrawal, and drug interaction. A roller coaster effect results from using stimulants for wakefulness and hypnotics for sleep. Polypharmacy is greatly reduced when a single physician manages the patient.
In the case of long-acting hypnotics, desired sleepiness at bedtime becomes a side effect in the morning. Half-lives of medications are sometimes overlooked as source of sleepiness and sleep disruption. In the elderly, standard adult dosages may need to be reduced, as the half-life is extended due to slower metabolism. In addition, patients with fragmented sleep periods throughout the 24-hour day, typically due to medical conditions, may be confused by directions to "take at bedtime" and may inadvertently increase the daily dosage.
Medical History
Many medical conditions affect sleep and careful history taking, including review of systems and a thorough physical examination are useful for identifying undiagnosed medical conditions that underlie a sleep complaint. A variety of medical, neurological, and mental disorders are associated with sleep disorders. (See Table 2.) In these conditions, a complaint of disturbed sleep often represents a secondary condition stemming from the underlying disorder such as diabetes and hyperthyroidism.17,18 Treatment plans should focus on the underlying disorder and attempt to minimize the symptoms during sleep. PSG is not indicated unless symptoms of sleep disorders such as sleep apnea or periodic limb movements during sleep are present.
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Physical Exam
A brief physical exam should be included with particular attention to weight change and the oral cavity. Increases in weight associated with the initiation of sleep symptoms is a common finding in obstructive sleep apnea (OSA) patients, and obesity is a risk factor for sleep-disordered breathing.19 Neck circumference is highly predictive of the likelihood of sleep apnea; a neck circumference of more than 17 inches in a man or 16 inches in a woman is associated with increased risk of sleep-disordered breathing.20
A crowded oral cavity and oropharynx is also suggestive of OSA, and findings may include a shallow oral pharynx, large tonsils and adenoids, large tongue, long uvula, and narrow opening between lateral pharyngeal walls.21 A receding chin is also likely to crowd the posterior airway, and is associated with sleep apnea.
Treatment Plans
Treatment plans are based on the problems identified in the sleep history and physical (H&P). Many sleep problems, such as circadian rhythm disturbances, do not require a PSG for diagnosis. Underlying medical and psychiatric problems should also be addressed directly. Sleep disorders that do not have a diagnostic marker or abnormality apparent in a sleep test do not require PSG testing. A PSG is not initially recommended in complaints of insomnia unless symptoms or descriptions of sleep apnea or periodic limb movements are reported.22 However, a PSG may be useful in insomnia, after other behavioral measures have been tried and other psychological and medical causes have been ruled out.
Symptoms suggesting a physiological abnormality during sleep or complaints of unexplained excessive sleepiness generally require PSG testing. A multiple sleep latency test (MSLT) should also be performed in patients with unexplained excessive sleepiness. The current standards of practice guidelines indicate that polysomnograms should be performed to evaluate sleep apnea, narcolepsy, or periodic limb movements during sleep.23 However, periodic limb movements of sleep have recently been demonstrated not to predict sleepiness,24 and many sleep clinicians discount this finding on PSG.
Quantification of sleep apnea is generally required before treatment is authorized.
Types of Sleep Studies
There are various types of sleep studies performed by sleep disorders programs. These include various tests during the patient’s sleep period as well as tests during their wake period. The patient’s sleep-wake schedule should determine when testing is done.
A polysomnogram should always be performed during a patient’s normal sleep time. Polysomnograms include recordings of the eyes (EOG), chin and legs electromyograms (EMG), electroencephalogram (EEG), electrocardiogram (ECG), oxygen saturation, and respiration. The initial PSG is referred to as baseline or diagnostic study. Polysomnograms done during the titration of positive airway pressure (PAP) are called titration studies. Titration studies may involve continuous positive airway pressure (CPAP) or bi-level PAP studies. Most sleep apnea patients have a diagnostic study followed by a separate titration study if needed.
In some cases, a baseline and titration study are performed during a single recording called a "split night" study. Split night studies are difficult; since the criteria for diagnosis must be estimated from the ongoing recording, the patient must be awakened and fitted with a PAP mask and then be able to return to sleep for an adequate amount of time to titrate the PAP in all sleep positions as well as REM sleep. If any criteria are not met, then repeat testing for a diagnostic baseline, titration, or both may need to be performed.
Two types of studies are performed during the wake period for evaluation of sleepiness and alertness. Nap studies, called the MSLT, are performed during the wake period to objectively measure daytime sleepiness or aid in the diagnosis of narcolepsy. The MSLT follows a polysomnogram and it consists of a series of naps to determine mean sleep latency. A related test is the maintenance of wakefulness test (MWT), and it is considered an objective measure of alertness. This test is similar to an MSLT except that the patient is told to try to stay awake. MWTs are typically done to evaluate the effectiveness of treatment and evaluate the work readiness of a patient. Results of MSLTs and MWTs are not highly correlated. The lack of a correlation between alertness and sleepiness measures suggests that these are not reciprocal systems and sleep and wake are not on a continuum. If the purpose of testing is to measure the degree of sleepiness or aid in the diagnosis of narcolepsy, the MSLT is the appropriate test. If there is concern about the patient’s ability to stay awake, the MWT is the preferred test.
Part II of this manuscript will explain basic data found in a sleep study report to enable the ordering physician to understand and interpret the results. Also, common sleep disorders encountered in primary practice will be discussed along with the current understanding of causes and treatment options.
References
1. National Commission on Sleep Disorders Research. Report of the National Commission on Sleep Disorders Research. DHHS Publication. Washington DC:U.S. Government Printing Office, 1992.
2. Leger D. The cost of sleep-related accidents: A report for the National Commission on Sleep Disorders Research. Sleep. 1994;17:84-93.
3. Gallop Organization. Sleep in America. Princeton, NJ: Gallop Organization;1995.
4. Leger D, et al. Prevalence of insomnia in a survey of 12,778 adults in France. J Sleep Res. 2000;9:35-42.
5. Ohayon MM, et al. SSM-IV and ICSD-90 insomnia symptoms and sleep dissatisfaction. Br J Psychiatry. 1997:171:382-388.
6. Bixler ED, et al. Prevalence of sleep disorders in the Los Angeles metropolitan area. Am J Psychiatry. 1979;136:1257-1262.
7. American Academy of Sleep Medicine. International Classification of Sleep Disorders. American Academy of Sleep Medicine 1997.
8. US Congress, Office of Technology Assessment. Biological Rhythms: Implication for the Worker. (OTA-BA-463) Washington, DC, US Government Printing Office.1991; September.
9. National Sleep Foundation: 2001 "Sleep in America" Poll. Press release: March 2001.
10. Bonnet MH, Arand DL. We are chronically sleep deprived. Sleep. 1995;18:908-911.
11. Kripke DF, et al. Mortality association with sleep duration and insomnia. Arch Gen Psychiatry. 2002;59:131-136.
12. Bonnet MH, Arand DL. Caffeine use as a model of acute and chronic insomnia. Sleep. 1992;15:526-536.
13. Stone BM. Sleep and low doses of alcohol. Electroencephalogr Clin Neurophysiol. 1980;48:706-709.
14. Kowatch RA, et al. Electorencephalograpic sleep and mood during cocaine withdrawal. J Addict Dis. 1992;11:21-45.
15. Obermeyer WH, Benca RM. Effects of drugs on sleep. Neurol Clin. 1996;14:827-840.
16. Rosen RC, Kostis JB. Biohavioral sequellae associated with adrenergic-inhibiting antihyertensive agents: A critical review. Health Psychol. 1985;4:579-604.
17. Sridhar GR, Madhu K. Prevalence of sleep disturbances in diabetes mellitus. Diabetes Res Clin Pract. 1994;23:183-186.
18. Huang YR, Wang GH. Study on quality of sleep and mental health in patients with hyperthyroidism. Chung Hua Hu Li Tsa Chih. 1997;111:257-260.
19. Strobel RJ, Rosen REC. Obesity and weight loss in obstructive sleep apnea a critical review. Sleep. 1996;19:104.
20. Rowley JA, Aboussouan LS, Badr S. The use of clinical prediction formulae in the evaluation of obstructive sleep apnea. Sleep. 2000;23:929-938.
21. Schwab RJ, Goldberg AN. Upper airway assessment-radiographic and other imaging techniques. Otolaryngol Clin North Am. 1998;31:931-968.
22. Chesson A, Jr, et al. Practice parameters for the evaluation of chronic insomnia. Sleep. 2000;23:237-241.
23. Polysomnography Task Force, American Sleep Disorders Associations Standards of Practice Committee. Practice parameters for the indications for polysomnography and related procedures Sleep. 1997;20:406-422.
24. Chervin RD. Periodic leg movements and sleepiness in patients evaluated for sleep-disordered breathing. Am J Respir Crit Care Med. 2001;164:1454-1458.
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Readers are invited to submit questions or comments on material seen in or relevant to Primary Care Reports. Send your questions to: Robin Mason, Primary Care Reports, c/o American Health Consultants, P.O. Box 740059, Atlanta, GA 30374. For subscription information, you can reach the editors and customer service personnel for Primary Care Reports via the internet by sending e-mail to [email protected].
Sleep disorders are extremely common and the primary care physician (PCP) can play an important role in their identification and management. The PCP is the first line of defense for identifying patients with sleep disorders and initiating appropriate evaluation and managing long-term treatment.
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