Excessive Daytime Sleepiness

Learn About Excessive Daytime Sleepiness

Excessive Daytime Sleepiness, or EDS, is a condition characterized by difficulty staying awake in the everyday course of living.  People with EDS are often tired, fatigued, and forgetful; they can have difficulty focusing or concentrating; and can be irritable and moody.  Measuring the degree of EDS is the job of the Epworth Sleepiness Scale, or ESS.  The ESS assigns a likelihood score to a patient-reported propensity to become sleepy in particular situations:  Watching TV; sitting and reading; being inactive in a public place like a theater or a meeting; as a passenger in a car; lying down to rest in the afternoon or sitting quietly after lunch; talking with someone, or while stopped for a few minutes in traffic.  The higher the ESS score, the more severe the problem of EDS.  

In addition to subjective measures of EDS, there are objective measures of daytime sleepiness, particularly the Multiple Sleep Latency Test, or MSLT.  The MSLT consists of five nap opportunities spaced two hours apart.  During these naps the patient is monitored to determine the time to onset of sleep (this is the sleep latency), as well as the level of sleep the patient attains to in the time allotted.  This test is especially pertinent to the diagnosis of narcolepsy, one of the conditions causing EDS (see Sleep Disorders V:  Narcolepsy).  The MSLT is often preceded by an overnight sleep study in the sleep lab, to assess the adequacy of nocturnal sleep and to identify nocturnal events potentially responsible for the daytime sleepiness.

The causes of EDS are many.  Neurologists encounter EDS as an associated feature of dementia, Parkinson’s disease or other neurodegenerative conditions, neuromuscular disorders, epilepsy, and chronic pain.  Sleep disorders associated with EDS include narcolepsy, obstructive sleep apnea, insufficient sleep hours, shiftwork, medications and substances of abuse, circadian rhythm disorders (Sleep Disorders III:  Disorders of Sleep Rhythm), and idiopathic hypersomnia (that is, severe excessive daytime sleepiness with no known cause).

Nocturnal causes for daytime sleepiness include sleep-related breathing disorders, which cause sleep to be fragmented and non-restorative.  In particular, during sleep breathing the airway becomes relaxed, allowing it to collapse upon inhalation.  The collapse can be complete (apnea) or partial (hypopnea).  Either way, the episode is terminated by an arousal in the brain – an awakening so brief that patients themselves are rarely aware of it, yet it is sufficient to restore muscle tone to the airway.  Other causes of sleep fragmentation include snoring, periodic movements of the limbs that are associated with brain arousals, any condition of a painful nature, epilepsy, asthma or other pulmonary disease, gastro-esophageal reflux disease, and irritable bowel syndrome.  

In addition to nocturnal causes of excessive daytime sleepiness, there is the primary disorder of alertness, narcolepsy.  Discussed in detail elsewhere (see Sleep Disorders V:  Narcolepsy), narcolepsy is basically a disorder of sleep intrusion into the activities of the waking state.  Other neurological disorders can also cause primary attenuation of waking alertness, such as the rare Kleine-Levin syndrome, which occurs predominately in adolescent males, and involves distinct periods of ravenous eating, hypersexuality, and aggression during which the person may sleep for upwards of 18 hours a day.  Finally, menstrually-related hypersomnia occurs during the few days preceding menses.

The first step in determining what the cause of EDS might be is to take a careful history and perform a symptom-based physical examination.  It is also quite helpful to have the patient maintain a sleep diary for a number of days or weeks to identify circadian or behavioral factors impacting the quality of nocturnal sleep, including primary insomnia, inadequate sleep hours, a disturbance of circadian rhythm, pain or other disorders causing multiple awakenings during the night, the use of caffeine or other stimulants too late in the day causing varying degrees of insomnia and a psychiatric illness such as depression.  

The treatment of EDS depends upon the cause.  Sleep hygiene refers to behavioral changes to promote nocturnal sleep and daytime alertness.  Stimulants or the alerting agents Provigil (modafinil) and Nuvigil (armodafinil) can help support alertness in patients with narcolepsy and idiopathic hypersomnia; but there are other treatments specific to narcolepsy such as certain antidepressants and gamma-hydroxybutyrate (Xyrem).  Continuous positive airway pressure, or CPAP, a device that uses a stream of air administered via a nasal mask to splint the airway open, can be used to remedy sleep-disordered breathing.  Antidepressants can help the patient with depression.  Lithium and anticonvulsants can be helpful in the management of the Kleine-Levin syndrome.  Finally, birth control pills can be useful for menstrually-related hypersomnia.

Mark J. Woyshville MD

Bibliograpy: LinkEpworth Sleep ScaleAAFP

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