A Multiple Sleep Latency Test – what does it measure?
Identifying sleep disorders is notoriously tricky, but one approach that has proved successful is the Multiple Sleep Latency Test. Also known as MSLT, this test measures how quickly you fall asleep during the day. From this, your doctor can begin to understand the issues you may be having and then develop a diagnosis.
The multiple sleep latency test is used to help physicians diagnose narcolepsy and idiopathic hypersomnia. These sleep disorders leave you feeling exhausted and needing sleep during the day. This MSLT, a daytime nap study, examines your sleep needs during regular waking hours.
Your doctor will require you to spend a whole day on the test to do this. Five naps will be scheduled during the day, each 2 hours apart. In a controlled environment, the test creates a quiet, comfortable space to sleep with all light blocked out. Once your clinician turns the lights off, the test measures how long it takes to fall asleep. After you fall asleep, somebody will wake you after 15 minutes. However, if you fail to fall asleep at all within 20 minutes of the test starting, that nap trial will end.
Photo by Polina Kovaleva
The Multiple Sleep Latency Test uses sensors to monitor your sleep behaviour accurately during each nap trial. They record whether you are asleep, the time it took to fall asleep, and your sleep stage. Together, this data lets your doctor understand the type of sleep you need during the day. From there, they can tell you the likely cause of the problem.
How can I prepare for an MSLT?
Any situation outside your everyday experience can be unnerving. The Multiple Sleep Latency Test requires you to sleep while being observed. This can be a challenge for all of us and a definite problem for your MSLT. In fact, several factors can influence the results and make it harder to diagnose your issue. These include:
- Age
- Level of sleep you had before the study
- Anxiety
- Caffeine intake
- Depression
- Drugs or medications you may have taken
- Tension
Avoiding these issues is essential to see the best results from your Multiple Sleep Latency Test. There are several things you can do to help, and these are steps your doctor may also recommend:
1. Maintaining a Sleep Diary
Before taking a multiple sleep latency test, your doctor will ask you to keep a sleep diary for two weeks. You will record your sleep patterns. This can help identify the problem, spot issues, and adjust to a regular sleep schedule.
2. Avoid Stimulants and Medications Where Possible
Think about how much caffeine you consume daily and talk to your doctor about it. They may suggest you reduce your intake or consider it during your test. You must discuss your medications, too, as you may need to stop taking some for a week or two before the MSLT. Do this to avoid contaminating the multiple sleep latency test results.
3. Recording Your Sleep
You must record a sleep diary the night before your multiple sleep latency test. For the test to offer valid results, you should sleep at least 6 hours during that night. The sleep study for the night can often reveal another possible sleep disorder, such as sleep apnoea.
4. Avoid Drugs
In addition to a sleep diary for the night before, if you do take drugs of any kind, you may need to undertake a drug test before your MSLT. This is because they may affect results, and the test will not be worth doing if you have high concentrations. The best advice, then, is to avoid drugs entirely for a few weeks before your multiple sleep latency test.
What is the difference between a Polysomnography and a Multiple Sleep Latency Test?
Polysomnography monitors you while you are asleep to analyse the depth and duration of various sleep stages. It also records your breathing and other average body functions to see how they are affected by sleep. The goal is to assess sleep quality, whereas in an MSLT, the goal is to see how sleepy you are.
Usually, your multiple sleep latency test will also record those data points for each short, 15-minute nap to help assess sleep patterns. However, the focus is always on how long it takes to get to sleep—how sleepy you are during the day.
Sometimes, you may take both tests, with the Polysomnography taken overnight and the MSLT taken over the next day.
How are MSLT results interpreted?
Sleep disorders are one of the more challenging diagnoses that your physician will undertake. This is partly because the causes of many sleep disorders remain unproven. But it is also because symptoms are so similar for many potential issues. With that in mind, you can expect to wait a couple of weeks or more to get any results from your multiple sleep latency test.
In general, tests can reveal an issue with the time it takes to get to sleep during the day. The type of sleep you experience during those naps tells your doctor the probable sleep disorder causing it.
If you suffer from narcolepsy, you will quickly cycle between sleep stages. Your doctor will look for two or more REM sleep stages during the multiple sleep latency test to show it as the most likely cause of your issue. However, idiopathic hypersomnia causes you to fall asleep in the day easily but prevents you from achieving REM sleep. So, suppose your test shows no REM sleep stages. In that case, it is more likely that idiopathic hypersomnia is the cause of your sleep problems.
Subsequently, your doctor will be able to create a suitable treatment plan to help you deal with the identified sleep disorder. Without a multiple sleep latency test, they could spend months identifying the issue.
Featured post photo by RDNE Stock project