Sleep Study Test Results Explained

How To Read and Understand Your Results When Testing for a Sleep Disorder

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Illustration of woman sleeping with sleep tracker during sleep study

There’s a lot of data to sift through after you have a sleep study performed, and we know it can be overwhelming to try and make sense of what looks like a seemingly random collection of letters and numbers. What do those numbers mean, why is there a graph, and what do all those acronyms stand for? 

Don’t worry – by the end of this article, you’ll have a much better understanding of what happens during a sleep study test and how to read your sleep study results.

Types of Sleep Studies

There are five main types of sleep studies: 

In-Lab Polysomnogram (PSG)

This is the preferred testing situation because everything happens within a controlled environment. During polysomnography, you’ll be connected to multiple wires and sensors that detect and monitor multiple important parameters like muscle movement, heart rate, brain activity, and breathing activity. 

Out of Center Sleep Test (OCST)

In this test, patients are sent home with small devices designed to allow the patient to perform the test at home. The kits consist of a pulse-oximeter, 1 or 2 strain gauges, and a nasal cannula. These tests can be less accurate because the home kits assume the patient is asleep without reading brainwaves.

Split Night Study

These are always in-lab PSGs where the technicians use the night’s first half as a diagnostic phase. If the patient shows significant sleep apnea, they are woken up and placed on a continuous positive airway pressure (CPAP) machine. Technicians then monitor the rest of the night to determine if the CPAP machine helped. 

CPAP Titration Study

These are in-lab PSGs where technicians use the entire night to adjust the CPAP to the patient’s personal needs. Doctors perform this study after an initial study determining sleep apnea.

Multiple Sleep Latency Test (MSLT)

The only sleep study done during the day, this test measures how fast a patient falls asleep in a quiet environment in the daytime. Doctors use MSLTs to diagnose narcolepsy and idiopathic hypersomnia. 

What Do Sleep Studies Test For?

When people think of sleep studies, they usually think of sleep apnea. However, doctors use these tests to diagnose a wide variety of disorders. 

Like many medical tests for disorders, doctors can’t test for something. Instead, they have to run tests to rule out other things. This way, they can narrow down the symptoms and data to understand what you’re struggling with. 

What Data Do Sleep Studies Collect? 

Though the doctor may have tested you for sleep apnea or because you can’t get an entire night’s sleep, the specialists look through various types of data to determine underlying conditions. This data includes:

  • Electroencephalogram for brain waves (EEG)
  • Electrooculogram for eye movements (EOG)
  • Electromyogram for muscle activity (EMG)
  • Electrocardiogram for heart measurements (EKG)
  • Sounds of snoring
  • Airflow efficiency and difficulties
  • Oxygenation
  • Video of the test to correlate tossing and turning with internal medical data

Man, that is a lot to get through. I know I couldn’t look at different charts and graphs for eight hours and get anything out of it. So, who does?

Sleep Study Scoring Service

A sleep study scoring service is a team of medical professionals specializing in reading and interpreting sleep study results. The group usually works under one or two “sleep doctors.” 

First, a sleep tech reviews the raw data and “scores” it into organized, clinical information. Then the information is sent to the sleep doctor, who re-reviews it and writes an explanation. The sleep study results interpretation is then passed to your primary doctor or referring clinician.

You may be able to skip the third party if you go to a sleep clinic with a scoring service offered in-house. This way, the data stays in one office, sometimes leading to a quicker turnaround time.

Diagnosing Sleep Disorders

There are many sleep disorders that doctors can diagnose thanks to sleep studies. Unfortunately, Insomnia and restless leg syndrome don’t have one diagnostic explanation. It can be a combination of medical history, a doctor’s opinion, and your own experiences.

Understanding Your Sleep Apnea Test Results

To understand your sleep study results, we’ll need to understand the Apnea Hypopnea Index (AHI). This is one of the most critical pieces of information evaluated. You may be thinking: Why do I need to learn about sleep apnea if that’s not why I’m taking the sleep test? 

Even if your doctor is not testing you for sleep apnea, you’ll still want to understand what the AHI means, and how to read a sleep study interpretation guidelines. The doctors can use the scoring to rule out sleep apnea and focus on other possible problems.

What is the AHI Scale?

Doctors use the AHI scale as a measurement tool to represent how often a patient stops breathing (or almost stops breathing) per hour. The AHI is the sum of apneas (pauses in breathing) added to the number of hypopneas (shallow breathing) that occur each hour.

The apneas and hypopneas need to last at least ten seconds at a time to be classified. After that, sleep technicians calculate your AHI score by dividing the number of combined events by the number of hours of sleep. 

For example, say you had 3 apneas and 6 hypopneas throughout a 9-hour night: 3+6=9, and 9/9=1. Therefore, your AHI score would be 1.

Understanding the AHI Scale Results

So, you’ve gotten a hypothetical AHI score of 1. Where does that place you in the results? Here is how to read sleep apnea results.

  • Less than 5: Normal, no sleep apnea
  • 5-15: Mild sleep apnea
  • 15-30: Moderate sleep apnea
  • More than 30: Severe sleep apnea

Congrats! Your score of AHI 1 puts you within the normal, no sleep apnea range. This allows your doctors to pursue different possible causes for your trouble sleeping. 

If your actual score falls within any of the other areas, your doctor may recommend you sit down and discuss treatment options for sleep apnea. This can entail seeing a specialist or speaking to someone at the practice. 

Understanding Your Results for Narcolepsy

The MSLT specifically helps test for narcolepsy because it’s the only sleep study done during the day. During an MSLT, the patient has five scheduled naps every two hours. During this time, the sleep techs hook the patient to sensors that help sleep technicians monitor their vital signs.

If a patient suddenly falls asleep during the test when they weren’t supposed to be napping, this can be a sign of narcolepsy. I know that passing out in the middle of the day sounds exactly like narcolepsy, but this is why the sleep study results are so important.

Loss of patient consciousness can be for many reasons, such as heat, blood pressure, or iron deficiencies. During a sleep study, the technicians can look for signs that directly correlate to narcolepsy (activated REM, lower heart rate, normal blood pressure, etc.).

Understanding Your Results for Periodic Limb Movement Disorder (PLMD)

To be diagnosed with PLMD, there has to be evidence of clinical history and unusual bioelectrical signals found in your polysomnography test results. 

If your sleep study results come back with an average AHI, but you’re still feeling restless and tired during the day, sleep technicians will begin to look at the EEGs and the EMGs for unusual signals between your brain and your limbs.

Understanding Your Results for Sleepwalking and Sleep Talking

Even if your spouse has an embarrassing clip of you talking in your sleep, your doctor may be hesitant to diagnose you with a sleep disorder. There are a lot of variables that can cause occasional sleep talking or sleepwalking. A sleep study helps determine if the problems are chronic and harmful to your health.

This is why sleep studies have a visual component when collecting data. Not only will any cameras record you walking around, but microphones also pick up any speech. These studies benefit those living alone and unable to record themselves at night.

The sleep techs will also consider the bioelectrical grams to prove the body is asleep while walking around and talking. Science is less of proving one thing and more of disproving another!

Understanding Your Results for REM Sleep Behavior Disorder

This disorder can take more than a sleep study to diagnose but does require a study for an official diagnosis. Results for a REM sleep behavioral study consist of visual and audio data while including all bioelectrical grams. 

FAQ’s

What Are Normal Sleep Study Results?

Normal sleep study AHI’s range from 1-5. Time spent in each sleep stage averages 5% in stage 1, 50% in stage 2, 20%-30% in stages 3&4. Those numbers don’t add up to 100%, but each stage varies by cycle. Adults should have four to six cycles per night. Abnormal sleep study results would be greater than 30 and indicate severe sleep apnea.

How Many Awakenings per Night Is Normal?

Most healthy adults wake up three to four times during a typical night. If you regularly wake up more than six times per night, reach out to your doctor and explain your symptoms.

How Long Do At Home Sleep Study Results Take?

Those who opt for the in-home testing option will likely get their results back in 10-14 business days.

Conclusion

When you receive a sleep study analysis, there’s a lot of data to look over. Your doctor will start with your AHI to confirm or rule out sleep apnea before moving on to the bioelectrical grams and video data. Overall, you want your night to have 

Nate Devore
Nate Devore
For over 15 years Nate has been obsessed with solving his own personal and difficult health challenges related to sleep, energy, and fatigue. As one of our sleep experts at sleeping.com, Nate is passionate about helping you get the best night’s sleep possible.

Medical Disclaimer: The content on this page should not be taken as medical advice or used as a recommendation for any specific treatment. Always consult your doctor before making any decisions.

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