Narcolepsy and sleep studies: What to expect
Fact-checked by If you’ve recently learned you have narcolepsy, your diagnosis was likely based on the findings from sleep studies — tests doctors use to identify patterns of disrupted sleep and their underlying cause.
Sleep studies generate a lot of data about how well you’re sleeping, how long you sleep for, and how normal your sleep cycles are. It can be hard to understand all of these test results and what they really mean for you.
Here is a breakdown of what sleep studies measure, what your results might mean, and why your doctor might need to run more tests later on.
Which sleep studies are used?
For doctors to diagnose your narcolepsy, you probably underwent two main sleep studies: an overnight polysomnography and a next-day Multiple Sleep Latency Test (MSLT).
- Polysomnography: This nighttime test assesses how much sleep you’re getting, your sleep quality, and how much time you’re spending in each stage of the sleep cycle.
- MSLT: This daytime test measures how quickly you fall asleep during scheduled nap times during the day.
Polysomnography and MSLT are typically performed in sequence, with polysomnography done overnight and MSLT done the next day. They usually require staying in a private room at a specialized sleep center.
With polysomnography for narcolepsy, sensors are placed on your body to record brain and muscle activity, heart rate, breathing, and eye movements while you sleep overnight. This test may have helped your doctors rule out other sleep conditions that could potentially be causing or contributing to your symptoms. It also helps them understand whether problems with your nighttime sleep might be interfering with daytime MSLT test results.
MSLT for narcolepsy involves sensors placed on your body while you take five scheduled naps throughout the day, each spaced two hours apart in a dark, quiet room. This narcolepsy test was likely key to reaching your diagnosis, helping your doctors identify daytime sleepiness and sleep cycle disturbances characteristic of narcolepsy.
Understanding your sleep study report
After your initial sleep study, the results were interpreted by a sleep specialist to determine if you had narcolepsy or another sleep disorder.
That report probably includes a lot of data about many aspects of your sleep. But to diagnose narcolepsy, two major things specialists look for are evidence of daytime sleepiness and disruptions in the rapid eye movement (REM) phase of sleep. People with narcolepsy generally enter REM sleep more quickly than what’s typically seen in those with a normal sleep cycle, including during the day.
Your polysomnography results may have looked normal — they often do for people with narcolepsy — but they may have shown signs that support a narcolepsy diagnosis. Among such signs are:
- falling asleep within five minutes
- entering REM sleep within 15 minutes of falling asleep
- spending more time in light non-REM sleep than average
However, these findings alone cannot definitively diagnose narcolepsy. Diagnostic criteria for the sleep disorder generally require that MSLT results also show that you:
- fell asleep in an average of eight minutes or less across the naps
- entered REM sleep during at least two naps, or at least one nap if you entered REM within 15 minutes during polysomnography
Data from these sleep studies can be complex, so there is not always a single thing that indicates a definitive diagnosis. Your doctors will have interpreted the results in the context of your broader clinical circumstances and can help explain to you in more detail how they arrived at your diagnosis.
Why you might need to be retested
While many people with narcolepsy will only need to have sleep studies done once, at the time of their diagnosis, there are certain circumstances where your doctor might recommend repeat testing. Possible reasons for this include:
- a doctor identified another sleep problem during polysomnography that needs to be addressed before your MSLT results can be properly interpreted, such as sleep apnea
- a medication or substance interfered with your test results
- the results were inconclusive for an unknown reason but your symptoms still point to narcolepsy
- additional documentation is needed for insurance companies or disability claims
In some cases, instead of or alongside an additional sleep test, a doctor may recommend a test to measure levels of the brain signaling molecule orexin in the spinal fluid. An orexin deficiency causes narcolepsy type 1, while people with narcolepsy type 2 may have normal orexin levels. Doctors may recommend this for:
- children
- adults with unusual cataplexy
- people who cannot discontinue medications that may interfere with the MLST
Preparing for a sleep study
Specialists at your testing center will provide you with specific instructions about how to prepare for a narcolepsy sleep study if you need repeat testing, but it may involve:
- Â tracking your sleep for 1-2 weeks with a sleep diary and/or a wearable device (actigraphy) to ensure that sleep deprivation will not affect your results and that your sleep study aligns with your personal sleep habits
- getting on a stable treatment regimen for other sleep disorders, such as apnea
- discontinuing or adjusting medications that could interfere with your sleep study results
Your care team will always tell you which medications or substances need to be stopped or adjusted before your sleep study, and how to do so safely.
Most sleep centers recommend packing for a sleep study as if you are staying overnight at a hotel. That may include bringing along a toothbrush, other toiletries, pajamas, a change of clothes, and medications. Comfort items and/or a book or activity to do in between MSLT naps might also be packed in your testing bag. Your care team can provide more information about what to expect during an MSLT at your specific sleep center.
Sleep studies for children and teenagers
Sleep studies for children and teenagers typically follow protocols similar to those for adult testing, but a parent or guardian may need to stay the night with younger patients.
The tests may also be adjusted to accommodate age-appropriate sleep needs, as children often require more sleep than adults. Protocols may also be adjusted for children with neurodevelopmental disorders or other special needs.
Narcolepsy News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
