Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence.
INTRODUCTION — Patients with excessive daytime sleepiness (EDS) have impaired function due to difficulty maintaining wakefulness or alertness at appropriate times during the day. Complaints of EDS, or related terms such as tiredness, fatigue, and lack of energy, constitute some of the most common issues presented to clinicians. EDS is important to recognize because it can signal an undiagnosed sleep disorder or other treatable conditions. In addition, EDS can have a negative impact on a broad range of activities and raise safety risks while driving or operating other machinery.
This topic provides a general overview of the epidemiology, etiology, clinical features, and diagnosis of disorders that cause excessive daytime sleepiness. Classification of sleep disorders, sleep deprivation, and quantification of sleepiness are discussed separately. (See "Classification of sleep disorders" and "Insufficient sleep: Definition, epidemiology, and adverse outcomes" and "Quantifying sleepiness".)
Excessive daytime sleepiness — Daytime sleepiness is defined as excessive when it causes a subjective complaint or interferes with function. The International Classification of Sleep Disorders, third edition (ICSD-3) defines EDS as the inability to maintain wakefulness and alertness during the major waking episodes of the day, with sleep occurring unintentionally or at inappropriate times almost daily for at least three months .
Hypersomnia — The terms hypersomnia and hypersomnolence are sometimes used interchangeably with EDS. The ICSD-3 defines hypersomnolence as excessive sleepiness when wakefulness is expected, and hypersomnia as a disorder characterized by hypersomnolence . (See 'Central disorders of hypersomnolence' below.)
Fatigue — Fatigue refers to a subjective lack of physical or mental energy. Clinical fatigue incorporates three components, present to variable degrees in individual patients: inability to initiate activity (perception of generalized weakness, in the absence of objective findings); reduced capacity to maintain activity (easy fatigability); and difficulty with concentration, memory, and emotional stability (mental fatigue) . (See "Approach to the adult patient with fatigue".)
In practice, patients may use terms such as fatigue, tiredness, low energy, and sleepiness interchangeably. Although successful distinction is sometimes possible and can lead to different diagnostic approaches, data from patients with sleep disorders suggest that the terms, as used and emphasized by patients, have significant overlap. As an example, among 190 patients with laboratory-confirmed sleep-disordered breathing, 40 percent identified lack of energy as their worst problem, about 35 percent identified tiredness or fatigue, and only 25 percent identified sleepiness as their worst problem . Furthermore, when a sleep disorder is treated, patients may report less fatigue, tiredness, and lack of energy, as well as less sleepiness .
EPIDEMIOLOGY — EDS is reported by 10 to 25 percent of the general population . The quality of the data is limited by use of subjective measures in almost all studies, and variability between studies in questions used to assess for EDS. EDS has been reported to decrease with age in some studies, and to increase with age in others. Most studies show an equal gender ratio or a female predominance of up to two to one [6-8].
In a prospective population-based study that included over 4000 women without sleepiness at baseline, EDS developed in 8 percent of women over a 10-year period . The strongest independent risk factors for incident EDS were insomnia and smoking; others included anxiety and/or depression, somatic symptoms, snoring, and obesity.
ETIOLOGY — The causes of EDS are numerous, and multiple factors may contribute in any one patient. Some of the most common causes of EDS are insufficient sleep, depression, medications, and comorbid medical and psychiatric disorders. Obstructive sleep apnea (OSA) is a common and treatable cause of EDS that may not be readily apparent by history; though less common, hypersomnias of central origin such as narcolepsy should also be considered (table 1). Rarely, somatic symptoms and malingering account for symptoms of hypersomnia.
Insufficient sleep — Insufficient sleep can be self-imposed or socially dictated, as in shift work or other forms of sleep restriction. It can also result from an underlying comorbidity such as depression, medical illness or pain. Certain medications and drugs of abuse can alter sleep quantity and quality. (See "Insufficient sleep: Definition, epidemiology, and adverse outcomes" and "Insufficient sleep: Evaluation and management" and "Sleep-wake disturbances in shift workers".)
Sleep disorders — Many sleep disorders can result in EDS, at least in part because of reduced total sleep time or fragmentation of sleep . These disorders include:
●Sleep-related breathing disorders (eg, OSA, central sleep apnea, sleep-related hypoventilation/hypoxemia syndromes) (see "Polysomnography in the evaluation of sleep-disordered breathing in adults" and "Overview of obstructive sleep apnea in adults" and "Central sleep apnea: Risk factors, clinical presentation, and diagnosis")
●Circadian rhythm sleep-wake disorders (eg, jet lag, delayed sleep-wake phase disorder, advanced sleep-wake phase disorder) (see "Jet lag" and "Delayed sleep-wake phase disorder" and "Overview of circadian sleep-wake rhythm disorders")
●Sleep-related movement disorders (eg, restless legs syndrome, periodic limb movement disorder) (see "Clinical features and diagnosis of restless legs syndrome/Willis-Ekbom disease and periodic limb movement disorder in adults")
Parasomnias are not usually associated with EDS. Insomnia can sometimes be associated with EDS, but more commonly insomnia is associated with fatigue. In fact, patients with insomnia often have difficulty napping or sleeping during the day. (See "Overview of insomnia in adults".)
Central disorders of hypersomnolence — Hypersomnias of central origin are also considered to be sleep disorders, but the primary complaint of EDS is not due to disturbed sleep or misaligned circadian rhythms . Disorders in this category include:
●Narcolepsy type 1 or type 2 (see "Clinical features and diagnosis of narcolepsy in adults")
●Kleine-Levin syndrome (including menstrual-related hypersomnia) (see "Kleine-Levin syndrome (recurrent hypersomnia)")
●Idiopathic hypersomnia (see "Idiopathic hypersomnia")
Medical disorders — Certain neurological disorders (eg, myotonic dystrophy, Parkinson disease, multiple sclerosis), genetic disorders (eg, Prader-Willi syndrome, Niemann-Pick type C), and medical conditions (eg, hypothyroidism, obesity, hepatic encephalopathy) have been associated with hypersomnia that appears to have a central origin and is not better explained by other primary sleep disorders, medication use, or substance abuse. In such cases, a diagnosis of hypersomnia due to a medical disorder is most appropriate . (See "Excessive daytime sleepiness due to medical disorders and medications".)
Psychiatric disorders — Excessive nocturnal sleep, daytime sleepiness, and excessive napping can be associated with psychiatric disorders (such as depression, anxiety, and somatic symptom disorder or related conditions) when the problem is not otherwise explained by medication use, substance abuse or a known medical condition . In particular, atypical depression and bipolar depression frequently present with hypersomnia. (See "Unipolar depression in adults: Assessment and diagnosis", section on 'Depressive episode subtypes (specifiers)'.)
Medications and substance abuse — A variety of medications can cause or contribute to EDS (table 1). Common offending agents include benzodiazepines, nonbenzodiazepine sedatives, antihistamines, anticonvulsants, opioid analgesics, sedating antidepressants, and antipsychotics. Drugs of abuse that can cause EDS include alcohol, narcotics, and stimulant withdrawal. (See "Excessive daytime sleepiness due to medical disorders and medications", section on 'Medications'.)
INITIAL EVALUATION — No one test is adequate to fully characterize EDS or diagnose its causes . The evaluation typically begins with a thorough history and physical examination. Additional subjective and objective tests can supplement the history.
History — In the evaluation of EDS, the history is directed at refining the complaint of sleepiness and identifying potential causes. The history should elicit a detailed description of the complaint, attempting to differentiate sleepiness from other common complaints such as fatigue, lack of energy or weakness. It may be helpful to explain the difference between the terms and to ask a series of targeted questions for each symptom (table 2) . Sleepiness manifests mainly during sedentary activities, in contrast with fatigue, which typically affects pursuit of more active goals. The clinician should ask specifically about the propensity to fall asleep in low stimulus situations, such as long drives, reading, watching television, talking on the phone, interacting with friends, and completing desk work.
The medication list should be reviewed for any potentially contributory agents (table 1).
As EDS is frequently a symptom of sleep deprivation or an underlying sleep disorder, a sleep history should be taken in all patients. A good sleep history includes detailed information about symptoms of disturbed sleep, the duration of the symptoms (ie, acute or chronic), and the sleep environment. The history should include information about sleep times, such as bedtime, duration until sleep onset, final awakening time, consistency of bedtimes and awakening times, nap times, and nap lengths. The patient should be asked about sleep problems, including the number and duration of awakenings over a typical 24-hour period or a week.
Patients who cannot provide an adequate sleep history or who report considerable day-to-day or night-to-night variability can be asked to complete a daily sleep log for one or two weeks. Sleep logs record sleep times, sleep problems, and subjective sleep quality, so that the clinician may review the information for diagnosis and evaluate treatment efficacy without being misled by recall errors (table 3 and table 4) .
The history should also probe for symptoms of specific sleep disorders:
●Loud or habitual snoring and witnessed apneas can suggest a diagnosis of obstructive sleep apnea. (See "Clinical presentation and diagnosis of obstructive sleep apnea in adults", section on 'Clinical presentation'.)
●Leg discomfort, and typically an urge to move, that occurs with rest, abates with movement, and worsens in the evening, or the history from a sleep partner of limb movements during sleep, can signal a sleep-related movement disorder. (See "Clinical features and diagnosis of restless legs syndrome/Willis-Ekbom disease and periodic limb movement disorder in adults".)
●Cardinal features of narcolepsy (cataplexy, sleep attacks, hypnagogic hallucinations, and sleep paralysis) are not always volunteered and may be elicited by a careful history. (See "Clinical features and diagnosis of narcolepsy in adults", section on 'Clinical features'.)
Patients should be screened for depression by asking about depressed mood, loss of interest or pleasure in activities, change in appetite or weight, psychomotor retardation or agitation, low energy, poor concentration, thoughts of worthlessness or guilt, and recurrent thoughts of death or suicide. We recommend using a simple two- or nine-item screening tool such as the PHQ-9, which is easy to use, reliable and valid in primary care settings (table 5). (See "Screening for depression in adults".)
Interviewing family members can be particularly informative. Sleepiness is not always obvious to the person suffering from it, and a spouse, family member, or friend can often provide helpful observations on the impact of the patient's EDS. Patients and families should also be asked whether sleepiness affects quality of life, relationships with others, ability to concentrate, work productivity, and mood.
Physical examination — In most cases, a patient with EDS will not show specific findings on examination. Falling asleep while waiting for the clinician, excessive yawning, difficulty keeping eyes open, and poor concentration may help support the history if present, but if absent do not exclude EDS. The physical exam can also provide clues to an underlying sleep disorder. As an example, excessive oropharyngeal tissue, retrognathia, large neck circumference and obesity may be seen in patients with OSA. (See "Clinical presentation and diagnosis of obstructive sleep apnea in adults", section on 'Physical examination'.)
Epworth Sleepiness Scale — The Epworth Sleepiness Scale (ESS) is a one-page questionnaire that asks respondents to estimate their likelihood in recent times of dozing off or falling asleep in eight sedentary situations such as sitting and reading, traveling as a passenger in a car for an hour without a break, or sitting quietly after lunch without alcohol (table 6) (calculator 1) . Respondents score each item from zero (would never doze) to three (high chance of dozing), and responses are summed to generate a total score ranging from 0 to 24.
ESS scores greater than 10 are considered abnormal and supportive of a complaint of EDS. The ESS is easy to administer and can be helpful in that a high score raises the likelihood that a patient's complaint is truly EDS as opposed to fatigue or low energy. The validity of the ESS and its advantages and disadvantages are discussed separately. (See "Quantifying sleepiness", section on 'Epworth Sleepiness Scale (ESS)'.)
ADDITIONAL TESTING — In many patients, the cause of EDS is apparent from the history and no further diagnostic testing is necessary. This may be the case in patients who take offending medications or in those with clear sleep deprivation, psychophysiological insomnia, or medical or psychiatric conditions known to be associated with EDS. In other patients, particularly those in whom the history and examination suggest the possibility of sleep-related breathing disorders (such as sleep apnea) or central disorders of hypersomnolence, additional formal testing in a sleep laboratory should be pursued.
Polysomnography — Polysomnography is recommended in the evaluation of EDS when suspicion is raised for OSA, other sleep-related breathing disorders, periodic limb movement disorder (PLMD), narcolepsy, other central hypersomnias, or seizures during sleep. Polysomnography can also help identify the cause of insomnia in patients who do not have clear reasons for insomnia by history and examination. (See "Overview of polysomnography in adults".)
Sometimes, the PSG shows evidence of recent sleep deprivation, such as short nocturnal sleep latency, increased overall sleep efficiency, or an increase in the expected amount of deep non-rapid eye movement (non-REM) sleep. However, the novel experience of a sleep laboratory and recording equipment can hinder rapid sleep onset, deep sleep, or expected amounts of REM sleep in many individuals, so the absence of these findings should not reduce concern for a complaint of EDS.
Polysomnography will be abnormal in a variety of sleep disorders. As examples:
●In OSA, PSG shows increased numbers of obstructive apneas, hypopneas, and respiratory effort-related arousals. (See "Clinical presentation and diagnosis of obstructive sleep apnea in adults", section on 'Diagnosis'.)
●In central sleep apnea, PSG shows increased numbers of central apneas, hypopneas, and arousals. (See "Central sleep apnea: Risk factors, clinical presentation, and diagnosis", section on 'Diagnostic criteria'.)
●In PLMD, PSG detects increased numbers of stereotyped jerking leg movements that may or may not be associated with arousals and fragmentation of sleep. (See "Clinical features and diagnosis of restless legs syndrome/Willis-Ekbom disease and periodic limb movement disorder in adults", section on 'Periodic limb movements of sleep'.)
●In narcolepsy, PSG may demonstrate spontaneous awakenings, mildly reduced sleep efficiency, and rapid eye movement sleep within 15 minutes of the onset of sleep. (See "Clinical features and diagnosis of narcolepsy in adults", section on 'Diagnostic evaluation'.)
Home sleep apnea testing — A patient with EDS whose history suggests OSA may be a candidate for home sleep apnea testing (HSAT). Although a variety of testing approaches are available, the most common are overnight cardiopulmonary recordings that record airflow, chest excursion, oxygen saturation, ECG, snoring, and position. Such studies do not record sleep. However, they may be appropriate and less expensive alternatives to PSG for patients with high pre-test suspicion for moderate to severe OSA, if they also have no medical conditions that could complicate interpretation (eg, congestive heart failure) and have little risk for other sleep disorders (eg, narcolepsy) that cannot be assessed by home studies.
When positive, HSAT can identify the patient as a candidate for treatment with continuous positive airway pressure. When negative, however, a HSAT must be followed by a laboratory-based PSG to show that the patient does not in fact have OSA that was missed. (See "Home sleep apnea testing for obstructive sleep apnea in adults", section on 'Diagnosis'.)
Multiple sleep latency test — The multiple sleep latency test (MSLT) should only be performed immediately after a PSG. It provides an objective assessment of an individual's tendency to fall asleep at different times throughout the day .
The test consists of five daytime nap attempts while sleep/wake states are recorded in a sleep laboratory . For results to be valid and reliable, patients must have had sufficient sleep the night before, must not have been sleep deprived recently, and when possible should not be taking – or have recently discontinued – medications that affect sleep or daytime sleepiness. In addition, naps should not be performed during a patient's usual sleep period. These issues may be more important for younger patients. (See "Quantifying sleepiness", section on 'Multiple sleep latency test (MSLT)'.)
The primary results obtained from the MSLT are the mean sleep latency (based on standard EEG, EOG, and EMG criteria) and the number of naps that include REM sleep (known as sleep-onset rapid eye movement periods, or SOREMPs). A mean sleep latency less than eight minutes is generally considered to be consistent with objective evidence of EDS, in a properly performed MSLT that follows sufficient nocturnal sleep (of at least six hours) on PSG during the previous night. Although this cut-point (eight minutes) divides a largely unimodal distribution, with normal individuals sometimes scoring lower and patients with sleep disorders sometimes scoring higher, mean sleep latencies less than eight minutes are considered supportive of several specific sleep disorders. As examples:
●A mean sleep latency less than eight minutes, plus two or more SOREMPs, support a diagnosis of narcolepsy in the appropriate clinical circumstances. (See "Clinical features and diagnosis of narcolepsy in adults", section on 'Diagnostic evaluation'.)
●A mean sleep latency less than eight minutes, plus fewer than two SOREMPs, can support a diagnosis of idiopathic hypersomnia in the appropriate clinical setting. (See "Idiopathic hypersomnia", section on 'Diagnostic evaluation'.)
In general, short mean sleep latencies on an MSLT are more informative than longer latencies. In other words, negative results (ie, sleep latency greater than eight minutes) should not be used to argue that a patient complaining of EDS is not in fact sleepy. Normal results on an MSLT can provide some reassurance, but cannot guarantee a patient's ability to remain awake when driving or during other potentially dangerous circumstances. (See "Drowsy driving: Risks, evaluation, and management", section on 'Polysomnography and other testing'.)
The MSLT is indicated when clinical suspicion exists for narcolepsy , and may be useful in other circumstances when an objective measure of sleepiness is desired. The test is not routinely indicated, however, in evaluation for suspected OSA, sleepiness due to medical or neurological causes, insomnia, or circadian rhythm sleep-wake disorders.
A related study, the maintenance of wakefulness test (MWT), is not routinely indicated in the initial evaluation of EDS. It may be considered to assess an individual's ability to remain awake when the inability to do so could constitute a public or personal safety issue . However, results must be integrated with findings from the clinical history and compliance with therapy, and normal MWT results do not guarantee adequate alertness and safety. Neither the MSLT nor the MWT have been well validated as predictive tools for accident risk in real world circumstances. Similarly, driving simulator studies can show some association with risk for real-world motor vehicle crashes but do not adequately predict risk at an individual level . (See "Quantifying sleepiness", section on 'Maintenance of wakefulness test (MWT)'.).
MANAGEMENT — Diagnosis of the cause for EDS is the first priority and dictates treatment approach. Treatment strategies can be highly variable and might include, for example:
●Behavioral counseling about insufficient sleep, poor sleep hygiene, or a circadian rhythm sleep-wake disorder (see "Insufficient sleep: Evaluation and management" and "Overview of circadian sleep-wake rhythm disorders")
●Mechanical treatment with continuous positive airway pressure (CPAP) or an oral appliance for obstructive sleep apnea (see "Management of obstructive sleep apnea in adults")
●Medication for restless legs syndrome/Willis-Ekbom disease (see "Treatment of restless legs syndrome/Willis-Ekbom disease and periodic limb movement disorder in adults")
●Changes in type or dose of medications that cause hypersomnolence (see "Excessive daytime sleepiness due to medical disorders and medications", section on 'Medications')
●Ongoing efforts to treat the underlying condition when EDS is due to medical or psychiatric problems, such as chronic pain or depression (see "Excessive daytime sleepiness due to medical disorders and medications", section on 'Evaluation and management')
WHEN TO REFER TO A SLEEP MEDICINE PHYSICIAN — A decision on referral of a patient with EDS will depend on the experience, subspecialty training, and comfort level of the practitioner, as well as local availability of appropriate specialists.
Some accredited sleep disorders centers require that a patient be seen by an affiliated sleep medicine physician before polysomnography or other testing. In such cases, the sleep medicine physician often directs treatment efforts as well. Other accredited centers will see some patients after they are tested and found to have a sleep disorder, or they will work with outside physicians who are comfortable with the diagnosis and treatment of sleep disorders.
SAFETY CONSIDERATIONS — Regardless of the underlying cause, EDS raises important considerations related to driving safety and other activities that are discussed in detail separately. (See "Drowsy driving: Risks, evaluation, and management".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (See "Patient education: Daytime sleepiness (The Basics)" and "Patient education: Sleep apnea (The Basics)" and "Patient education: Jet lag (The Basics)" and "Patient education: What is a sleep study? (The Basics)".)
SUMMARY AND RECOMMENDATIONS
●Excessive daytime sleepiness (EDS) is defined as inability to maintain wakefulness or alertness during the major waking episodes of the day. It is distinguished from fatigue, which refers to a subjective lack of physical or mental energy. (See 'Definitions' above.)
●The causes of EDS are numerous and include at least four broad categories: insufficient sleep, sleep disorders, medical and psychiatric conditions, and medications. (See 'Etiology' above.)
•Insufficient sleep can be self-imposed or a consequence of work and other external obligations.
•Sleep disorders that contribute to EDS include sleep-related breathing disorders such as obstructive sleep apnea (OSA), circadian rhythm sleep-wake disorders, and central disorders of hypersomnolence, such as narcolepsy.
•Neurological, psychiatric and medical conditions such as chronic pain can be associated with hypersomnia that is not otherwise explained by a sleep disorder or medication side effects.
•Common medications associated with EDS include benzodiazepines, nonbenzodiazepine sedatives, antihistamines, opioid analgesics, anticonvulsants, and antipsychotics.
●The most important tool in the evaluation of a patient with EDS is the history, including a detailed sleep history, looking for clues to an underlying sleep disorder or explanation for insufficient sleep. The Epworth Sleepiness Scale (ESS) is a standardized measure of subjective sleepiness that is not diagnostic but can be useful in clinical practice. Additional objective testing in the sleep laboratory can also be helpful. (See 'Initial evaluation' above.)
●A polysomnogram should be ordered when the clinician suspects OSA, other sleep-related breathing disorders, periodic limb movement disorder, narcolepsy, other central hypersomnias, seizures during sleep, or unexplained insomnia. (See 'Polysomnography' above.)
●A home sleep apnea test may be an appropriate alternative to polysomnography in a sleep laboratory when a patient's history and physical exam suggest high pretest probability for moderate to severe sleep apnea. (See 'Home sleep apnea testing' above.)
●The multiple sleep latency test (MSLT) or its variant, the maintenance of wakefulness test (MWT), is indicated and should be performed immediately after polysomnography when clinical suspicion exists for narcolepsy or other disorders of central hypersomnolence, or when objective assessment of daytime sleepiness is desired. (See 'Multiple sleep latency test' above.)
●Regardless of the underlying cause, EDS raises important considerations related to driving safety and other activities. (See "Drowsy driving: Risks, evaluation, and management".)
- American Academy of Sleep Medicine. International Classification of Sleep Disorders, 3rd ed, American Academy of Sleep Medicine, Darien, IL 2014.
- Markowitz AJ, Rabow MW. Palliative management of fatigue at the close of life: "it feels like my body is just worn out". JAMA 2007; 298:217.
- Chervin RD. Sleepiness, fatigue, tiredness, and lack of energy in obstructive sleep apnea. Chest 2000; 118:372.
- Chotinaiwattarakul W, O'Brien LM, Fan L, Chervin RD. Fatigue, tiredness, and lack of energy improve with treatment for OSA. J Clin Sleep Med 2009; 5:222.
- Young TB. Epidemiology of daytime sleepiness: definitions, symptomatology, and prevalence. J Clin Psychiatry 2004; 65 Suppl 16:12.
- Hublin C, Kaprio J, Partinen M, et al. Daytime sleepiness in an adult, Finnish population. J Intern Med 1996; 239:417.
- Baldwin CM, Kapur VK, Holberg CJ, et al. Associations between gender and measures of daytime somnolence in the Sleep Heart Health Study. Sleep 2004; 27:305.
- Hara C, Lopes Rocha F, Lima-Costa MF. Prevalence of excessive daytime sleepiness and associated factors in a Brazilian community: the Bambuí study. Sleep Med 2004; 5:31.
- Theorell-Haglöw J, Åkerstedt T, Schwarz J, Lindberg E. Predictors for Development of Excessive Daytime Sleepiness in Women: A Population-Based 10-Year Follow-Up. Sleep 2015; 38:1995.
- Chesson AL Jr, Ferber RA, Fry JM, et al. The indications for polysomnography and related procedures. Sleep 1997; 20:423.
- Chervin RD. Use of clinical tools and tests in sleep medicine. In: Principles and Practice of Sleep Medicine, Kryger MH, Roth T, Dement WC (Eds), Elsevier Saunders, St Louis 2011. p.666.
- Bodkin CL, Manchanda S. Office evaluation of the "tired" or "sleepy" patient. Semin Neurol 2011; 31:42.
- Carney CE, Buysse DJ, Ancoli-Israel S, et al. The consensus sleep diary: standardizing prospective sleep self-monitoring. Sleep 2012; 35:287.
- Johns MW. A new method for measuring daytime sleepiness: the Epworth sleepiness scale. Sleep 1991; 14:540.
- Richardson GS, Carskadon MA, Flagg W, et al. Excessive daytime sleepiness in man: multiple sleep latency measurement in narcoleptic and control subjects. Electroencephalogr Clin Neurophysiol 1978; 45:621.
- Littner MR, Kushida C, Wise M, et al. Practice parameters for clinical use of the multiple sleep latency test and the maintenance of wakefulness test. Sleep 2005; 28:113.
- Schreier DR, Banks C, Mathis J. Driving simulators in the clinical assessment of fitness to drive in sleepy individuals: A systematic review. Sleep Med Rev 2017.