Understanding Your Sleep Study Results

If you recently had or ordered a sleep study to test for sleep apnea, the question foremost in your mind is probably what your results have to say about your sleep health or the health of your patient.

However, unless you know what to look for, your sleep study report may seem more perplexing than informational.

Here are six things you need to know in order to be able to read and understand a sleep study report.

Note: You should review your results with your physician and discuss your diagnosis, next steps and treatment options.

1. The first number you should look for: the AHI or RDI

Also known as the apnea/hypopnea index, this statistic is the definitive metric in determining if a patient suffers from sleep apnea. It counts the average number of apneas and hypopneas—in other words, respiratory events that cause a significant decrease in airflow— that the patient experiences per hour.

A quick look at this number can give you an idea of where you or your patient falls on a scale of sleep apnea severity.

AHI and Severity of Sleep Image

2. Other sleep disruptions: arousals, leg movements

It’s called sleep apnea for a reason, right? In fact, it turns out that this name is a very limited picture of respiratory and brain-related events that can disrupt a patient’s sleep.

Many different events can be of concern. Apneas are probably the most well-known characteristic of this sleep disorder; they occur when a patient’s breath stops completely for at least ten seconds. But a hypopnea, a partial cessation of airflow, can be just as serious. There are also RERAs (respiratory effort related arousals) that can disrupt the breath or depth of sleep without qualifying as either of the two above events. Furthermore, the sleep study should pick up on any arousals (partial awakenings) or excessive movements of the legs. All of these factors should be taken into account when assessing sleep quality and considering treatment options.

Learn more about apneas, hypopneas and arousals here.

3. Sleep stages

During the night, humans progress through several sleep stages, known as N1, N2, N3, and REM sleep.

Adults typically cycle through the stages in that order multiple times per night. However, certain sleep disorders can disrupt and fragment this cycle, making it impossible for patients to achieve normal, revitalizing rest. For instance, sleep apnea can result in arousals that prevent people from ever sinking into the deepest stage of sleep that they need to feel recharged in the morning.

During the sleep study, brain monitors will keep track of which stage of sleep you are experiencing and will allow technicians to observe any irregularities.

For some people, sleep apnea is worse during REM sleep. A 2012 study in the Journal of Clinical Sleep Medicine analyzed 300 sleep studies and found that half of patients had a 2x increase in AHI while in REM sleep.

4. Body position

Similar to sleep stages, body position can also impact the severity of sleep apnea. The same 2012 Journal of Clinical Sleep Medicine study that analyzed 300 sleep studies found that 60% of patients had a 2x increase in AHI while sleeping on their backs. This is why the sleep technician will try to get each patient to sleep on his/her back for at least a portion of the sleep study.

The sleep study should show how much of your sleep time was spent on your right side, left side, prone (on your stomach) and supine (on your back).

5. Oxygen desaturation (SaO2)

If you stop breathing repeatedly during sleep, you’re not getting the amount of oxygen into your bloodstream that you need. Your oxygen saturation (SaO2) measures the percentage your body’s oxygen capacity that is actually being inhaled. In people with very severe sleep apnea, their oxygen levels can fall as low as 60% of ideal or lower during sleep—meaning that they are absorbing slightly over half the oxygen they need to function.

If your saturation dips anywhere below 95%, your brain and body are not getting enough oxygen. This can cause brain damage and serious cardiovascular problems. Fortunately, you can ensure you are getting the airflow you need by using a PAP (positive airway pressure) device, which will restore you to normal breathing and a good night’s sleep.

Check out this post to learn more about how oxygen saturation is measured during a sleep study.

6. Recommended therapy or next steps

Depending on the findings of your sleep study, the interpreting physician may recommend another sleep study or CPAP therapy. Here are a few examples of the most common next steps after completing a sleep study (learn more about the different types of sleep studies here):

  • If you had a baseline PSG only which showed sleep apnea, you may need to return for a CPAP titration.
  • If your CPAP titration was not complete, you may need to return for another CPAP titration or a bi-level titration (learn more about the different types of PAP devices here).
  • If you had a successful CPAP titration, you may need to schedule a CPAP set-up.
  • If you had a home sleep apnea test (HST) you may need to have an in-center study, titration or autoPAP titration at home.
  • If your doctor suspects narcolepsy, you may need to return for a PSG & MSLT.



Other posts you may find interesting:

Editor’s Note: This post was originally published in November 2015 and has been edited and updated for accuracy and comprehensiveness.


  1. Anne Reply

    How can two sleep studies have different results? One study says I need to be on a CPAP the other one says I don’t. Now on one study I was on my anxenity meds the other I wasn’t could this change the effect of it.

  2. Julia Rodriguez Reply

    Hi Anne. Each sleep study is based on a different night of recorded sleep data, so yes, you could have different results in two sleep studies. It’s best to speak with your doctor or a sleep specialist as to why this occurred and how you should proceed. Good luck!

  3. Sandra C King Reply

    I have had two sleep studies. My cpap machine broke down after 8 years of use. I have Humana gold Medicare. I have been trying to get a new cpap machine for months, they tell me they need a BASELINE sleep study. They have both sleep studies. What is this? How do I get it? I need a cpap.

    • Anna Reply

      Medicare most likely needs a baseline study that is more recent that 8 years old.

  4. Sharon Reply

    I’ve been on cpap machine 2 years and just last couple of months I have been really tired what could be happing that iam tired

  5. Sharon Reply

    My ahi is 0.9 is that normal

  6. WILLIAM Banning Reply

    Just had a sleep study, I have anxiety so a lot of restless nights. Wake up every hr or so. The person doing the exam said I have more “events” when tossing and turning then while asleep. What does this mean?

  7. John Reply

    What if you need to wear a cpap machine but you cant sleep with one on. What are some alternatives.

  8. jenniferemmer Reply

    Hey, thanks for sharing the information. Sleep is a basic need. In Maslow’s hierarchy of Needs, sleep is defined as a Basic need, along-with food, drink, shelter and oxygen. Sleep is necessary for a person to survive. We are here to help you understand more about the importance of sleep and help you sleep better.

  9. Lonnie Cummins Reply

    So what does this mean? Do I have Sleep Apnea?

    This study is limited due to reduced total sleep time of 35 minutes, hence
    the results may not be valid. Mild snoring was heard intermittently. The total
    AHI was 18.9 events/hr. There was no REM sleep during the study night. The
    supine AHI was 21.6 events/hr.

  10. Lonnie Cummins Reply

    Sorry…Here is the complete report from above post:

    Diagnostic Polysomnography, 8/31/20, signed by ,
    1. This study is limited due to reduced total sleep time of 35 minutes, hence
    the results may not be valid. Mild snoring was heard intermittently. The total
    AHI was 18.9 events/hr. There was no REM sleep during the study night. The
    supine AHI was 21.6 events/hr.
    2.There was no associated episodic hypoxemia. There was no baseline
    oxyhemoglobin desaturation.
    3. There were no clinically meaningrul periodic limb movements of sleep during
    the limited time he slept.
    4. There were no seizures or parasomnias noted; there was normal attentuated
    muscle tone during REM (however, above states no REM sleep).
    5. EKG showed occasional ectopic beats. Clinical correlation advised.
    Diagnosis: Snoring
    1. A referral to sleep clinic is recommended. The patient may benefit from a
    usage of sleep aid before repeat sleep study if clinically indicated.
    2. Limited 1 lead EKG showed occasional ectopic beats which if new may need
    further work up like 12 lead EKG etc. Clinical correlation advised.
    3. If sleepy, the patient should be cautious in circumstances where difficulty
    maintaining alertness would be hazardous.

    • Jonathan Sherrill Reply

      Lonnie, if you would like to discuss your sleep study results in detail, please call me at 310-877-0167. Jonathan Sherrill-General Manager

  11. Lisa Price Reply

    I do not have restful sleep. I have dark circles under my eyes. I toss and turn at night. I can’t breath through my nose when I lay down-mouth breather. Two sleep studies show no apnea but a breathing issue. I’ve had a septoplasty and Rhin air procedure. I still do not restful sleep.

  12. High Rated Gabru Reply

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  13. Rose Reply

    I see that this post is quite old but I just got my sleep study results back and I don’t know if it’s bad or good? To me it sounds bad from what I’ve gooogled but I’m not a dr..

    So here it is. Will I have to use a cpap mask? My good friend passed away from sleep apnea and now I’m afraid to go to sleep as silly as that sounds..

    FINDINGS: The recording initiated 1:22 AM and ended 7:57 AM. There were 6 hours, 22 minutes of satisfactory raw data available for air flow evaluation.

    There were a total of 112 apneas. There were 129 hypopneas using 4 percent desaturation criteria. The apnea indices were obstructive 5.2, central 12.4, and mixed 0.0 per hour. Cheyne-Stokes respirations were absent.

    The overall apnea-hypopnea index (AHI) was 37 events per hour (using CMS/Medicare scoring).

    There was 68 percent of study time spent supine. The AHI while supine was 52 per hour and non-supine was 5 per hour.

    The average pulse rate was 60 beats per minute. The average oxygen saturation was 91 percent. The lowest saturation recorded was 82 percent. The time spent with oxygen saturation less than or equal to 88% was 45 minutes.

    IMPRESSION: The home sleep test confirms severe obstructive sleep apnea. Findings include an overall apnea-hypopnea index (AHI) of 37 events per hour (using CMS scoring). The breathing disorder includes a mixed pattern of obstructive apneas and central apneas, together with significant oxygen desaturations (hypoxemia).

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  15. sherry d broughton Reply

    I was diagnosed with sleep apnea 5 years ago. I just took a second test. The technician stated if I start snoring or stop breathing, she will come place me on a machine. She never came in. I am hoping I no longer require this. I am exhausted after using the CPAP. I rest better without it.

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  17. canlitv Reply

    Hello, a debt of gratitude is in order for sharing the data. Rest is a fundamental need. In Maslow’s order of Needs, rest is characterized as a Basic need, alongside food, drink, haven and oxygen. Rest is fundamental for an individual to get by. We are here to assist you with seeing more with regards to the significance of rest and assist you with dozing better.

  18. Avery Smith Reply

    Apneas are probably the most well-known characteristic of this sleep disorder; they occur when a patient’s breath stops completely for at least ten seconds.

  19. Sandra Reply

    My husbands sleep study results show:
    Under component: sleep study reduced
    Value: no
    The test was a Polysomnography 4 or more parameters.
    He currently uses a bi-pap machine and we expected to see values after this test. Can you explain this to us?

  20. Carissa Cunningham Reply

    I just wanted to see if you could answer a few questions please? I live in a very small town so unfortunately our Drs are far behind other areas. I’m a 38yr women & had a study done when I was about 22yrs old. It did show I stop breathing a mid amount but she said “you have the biggest pain spirals I’ve ever seen on a scan before” what does that mean? My old Dr didn’t do anything after the test or discuss it. I have had health problems since childhood, 10 surgeries 2 on my brain (years after the study), seizure disorder, ect. I just wanted to know what she meant by that & what or if my brain condition cavernous malformation could have caused this? I would so appreciate an answer finally because my primary Dr isn’t even a primary we just don’t have enough Drs here so they tryish.
    Thank you
    Carissa Cunningham

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  24. spin the wheel Reply

    Because each sleep study is based on a separate night’s worth of data, the results from two sleep tests may change. It’s better to consult with a doctor or a sleep specialist to find out why this happened and what you should do next.

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