Multiple Sleep Latency Test
Overview of Multiple Sleep Latency Test
The Multiple Sleep Latency Test (MSLT) is a nap study used to assess how quickly a person falls asleep during the day. The test measures how much time elapses between starting to nap and the first signals of sleep, called sleep latency. Sleep centers offer multiple sleep latency testing as a way for doctors to diagnose excessive daytime sleepiness. Excessive daytime sleepiness is a condition wherein a person feels sleepy during waking hours for no apparent reason, in settings where other people are normally more awake and alert, such as at work or while driving. Diagnosable daytime sleepiness affects only about 5 percent of Americans, but it can indicate the presence of rarer sleep disorders such as narcolepsy.
The MSLT was created on the basis that a sleep doctor can measure how sleepy a person is by measuring how quickly and how often that person can fall into deep sleep during the day. As a person’s level of sleepiness increases, it theoretically takes an increasingly shorter amount of time for that person to enter rapid eye movement sleep, or REM sleep. During an MSLT, sleep doctors equip the patient to wires and sensors designed to monitor brain activity, heart rate and facial muscle movement. The end result of the MSLT is a detailed record of how quickly and how often a person is able to enter the REM stage of sleep when asked to nap during the day.
Multiple Sleep Latency Test Procedure
During a multiple sleep latency test, external factors such as temperature, noise, and light, which can make it difficult to fall asleep, are controlled as best as possible. The MSLT test is not completely objective, however, as inherent tension, stress, anxiety, depression and day-of factors, such as how well the person slept the night before or what he or she ate or drank that morning, may still affect test results. Approximately 2 weeks before undergoing an MSLT, patients are typically asked to stop taking any regular stimulant medications.
On the day of the multiple sleep latency test, patients cannot smoke or consume caffeine. Generally, a polysomnography or overnight sleep study will have been conducted on the night preceding the nap study. The patient has generally had at least 6 hours of monitored sleep, via the sleep study, and the MSLT serves as an expansion of the test. The MSLT is performed 1 to 3 hours after the sleep study is over, so that doctors who suspect the presence of hypersomnia or narcolepsy can gather additional information before making an official diagnosis.
During the MSLT, patients are given 4 to 5 opportunities to nap, with approximately 2-hour breaks in between each nap. If someone can’t fall asleep within 20 minutes, the test is usually cancelled, as this makes it quite unlikely that the test will lead to a diagnosis of narcolepsy or hypersomnia. Approximately 15 minutes into each nap, the patient is woken up and asked to keep active and awake until it is time for the next nap trial to begin. Once enough data is collected, the MSLT is over and the patient can leave the sleep center.
Following Up with Multiple Sleep Latency Test Results
Data collected from the multiple sleep latency test is taken to a board-certified sleep specialist who can analyze it effectively. Records of the patient’s sleep-wake cycle are then charted and evaluated by sleep doctors. If a sleep disorder is present, the physician will be able to see evidence of abnormal sleep patterns in the charts.
Overall, results of a nap study usually take about 2 weeks to process. Sometimes the attending sleep doctor will order additional tests during this time or talk to the patient’s primary care doctor to gather more information before making a diagnosis. Patients will have a follow-up appointment with whichever doctor that ordered the multiple sleep latency test to discuss the results. If a sleep disorder has been detected, the sleep center will start on an appropriate treatment plan.
If you have a history of narcolepsy in your family or if you notice symptoms of excessive daytime sleepiness, then find a sleep center that offers overnight sleep study and multiple sleep latency testing. You may be a perfect candidate for a nap study.