Multiple Sleep Latency Test and Maintenance of Wakefulness Test



Multiple Sleep Latency Test and Maintenance of Wakefulness Test


David Moore

S. Justin Thomas







The American Academy of Sleep Medicine (AASM) has defined excessive daytime sleepiness (EDS) as sleepiness occurring in a situation when an individual would be expected to be awake and alert (1). Excessive sleepiness is a complex issue that has had a profound impact on society. The cost of accidents due to excessive sleepiness has been estimated at approximately $43.15 to $56.02 billion during 1988 alone (2). Although these figures were criticized as overestimated (3), even a fraction of this amount would be a costly figure. Furthermore, it is important to recognize that when these accidents include the loss of life, the cost is incalculable.

Sleepiness on the job may cause accidents in the workplace. It is estimated that 42% to 49% of commercial vehicle accidents are caused by sleepiness or inattention. Twenty-five percent of Americans perform shift work (most of these in the transportation industry) and 4% work nights (2). Considering that humans are not biologically wired to be nocturnal, attempting to work during one’s biologically natural sleep time produces a tendency to be sleepy while at work. Additionally, shift workers often have to take extreme measures to sleep efficiently during the day. This leads to a generally sleepy working population at risk for accidents. Ironically, most sleep technologists have worked or currently work nights. It is not unusual to hear stories of fellow sleep technologists who have had trouble with sleepiness, including falling asleep while driving home.

The total number of motor vehicle accidents and ensuing fatalities due to sleepiness reported in the literature varies greatly from 1% to 41.6% (2, 4). The variation in these reports may be due to several factors. Until recently, the issue of sleepiness in relation to accidents has not been routinely assessed, and in many cases, the individuals involved are unaware of falling asleep or will not admit to falling asleep at the wheel at the risk of assuming responsibility for an accident. Unlike alcohol-related accidents, there is no blood test to determine one’s level of sleepiness when an accident occurs, and therefore, sleepiness is often merely speculation. However, the association between sleepiness and motor vehicle accidents is undeniable. In clinical situations, large numbers of patients with diagnosed sleep disorders report having had motor vehicle accidents (2). Furthermore, when polled, nine out of ten police officers had pulled over at least one motorist under the suspicion of driving under the influence when the person was actually sleepy. The National Highway Traffic Safety Administration reported that between 2009 and 2013, drowsy driving resulted in an average of 72,000 crashes, 44,000 injuries, and 800 deaths per year (5).

As sleepiness becomes a recognized problem in society, the role of the sleep center in documenting pathologic sleepiness has increased in importance. However, measuring sleepiness is a difficult and often an elusive task. Several scales, such as the Epworth Sleepiness Scale and the Stanford Sleepiness Scale, have been developed to subjectively measure sleepiness. Because of their subjective nature, these scales are used in conjunction with the sleep history and more objective measures to aid in the diagnosis of sleep disorders. Objective measures of
sleepiness are the multiple sleep latency test (MSLT) and the maintenance of wakefulness test (MWT).

The MSLT measures one’s tendency to fall asleep. It is used as part of the evaluation of patients with suspected narcolepsy and may be used in evaluating patients with suspected idiopathic hypersomnia (1). The MSLT consists of five nap opportunities, each separated by 2 hours. A shorter four-nap test may be performed; however, this test is not reliable for the diagnosis of narcolepsy unless at least two sleep-onset rapid eye movement (REM) periods (SOREMPs) have been recorded (1). The MWT measures one’s ability to resist the urge to fall asleep. The MWT may be used to evaluate treatment response or to assess patients whose inability to remain awake may constitute a public or personal safety issue (1). The MWT consists of four 40-minute trials, each separated by 2 hours. Currently, the MSLT and MWT are the only objective measures available to the clinician to quantify sleepiness in a patient. They should be used in conjunction with other clinical information to determine the correct diagnosis and best course of treatment. The importance of quantifying sleepiness lies in the impact that sleepiness has on the patient and society as a whole. In this regard, technologists play an important role in the diagnosis of the disorders of excessive sleepiness.




Dec 12, 2019 | Posted by in NEUROLOGY | Comments Off on Multiple Sleep Latency Test and Maintenance of Wakefulness Test

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