What do AHI, RERA, Arousal and RDI mean? (2023)

After your sleep study for medical practices

What do AHI, RERA, Arousal and RDI mean? (1)

What do these terms mean in a sleep study report?

Which one do insurers use to determine eligibility for CPAP therapy?

Learn about the different types of respiratory events, how they are assessed, and what they mean for CPAP therapy treatment options and insurance coverage.


It is the average number of combined apneas and hypopneas per hour. It is most commonly used to determine the severity of a person's sleep apnea.

What is Free Diving?

Apnea is when you stop breathing for at least ten seconds while you sleep. The figure below shows how sensors used during a sleep study measure your breathing. This criterion is used to evaluate a sleep study. This is the part of the process where a technician reviews the recorded data from your overnight sleep study.

What do AHI, RERA, Arousal and RDI mean? (2)

Different types of freediving:

  • Apnea:The signals shown above drop at least 90% for at least 10 seconds.
  • Obstructive sleep apnea:Meets criteria for apnea (above) and sustained or increased respiratory effort is seen (exertion is due to airway obstruction, learn more)Here).
  • Central apnea:Apnea without respiratory effort throughout (this is a neurological problem, learn more about central sleep apnea)Here).
  • Mixed Apnea:An apnea without respiratory effort at the beginning of the test, followed by respiratory effort in the second part of the test.

What is hypopnea?

Hypopnea is a significant reduction in airflow during sleep (not a complete cessation) that causes a drop in blood oxygen saturation and then awakening.

Two ways to calculate hypopnea (according to Medicare, see link in sources):

(1)50% reduction in airflow at 3% blood oxygen desaturation

(2) 30% reduction in airflow at 4% blood oxygen desaturation

What do AHI, RERA, Arousal and RDI mean? (3)

Activation of respiratory effort.

Event that causes excitement or decreased oxygen saturation without qualifying as apnea or hypopnea.

Arousal is when sensors that measure brain activity, called EEGs, show brain waves changing into an alpha waveform. It means you woke up, even if you don't realize it. It is the repeated awakening of your brain as a result of a breathing disturbance lasting at least 10 seconds that causes sleep apnea damage, regardless of the type of event that occurs or whether the pause in breathing is a complete pause or a partial pause. As a result, many sleep centers and insurers are starting to recognize the RERA as an indicator of disease severity.

What do AHI, RERA, Arousal and RDI mean? (4)

index of respiratory disorders.

This is the combined number of apneas, hypopneas and RERA per hour of sleep. Clinicians who use this scale generally follow the same guidelines used for the Apnea/Hypopnea Index (AHI).

Medicare defines the RDI as the average number of apneas and hypopneas (so it's really the same as the AHI), it doesn't include the RERA.

Most commercial insurance refers to AASM standards, which include apneas, hypopneas, or RERA.

As detailed above, the AHI is the traditional measure used to determine the severity of sleep apnea; However, many institutions and insurers consider RERAs because any respiratory event that lasts at least 10 seconds and causes arousal can be harmful and must be treated. The following table lists the AHI criteria, but RERA should also be considered.

None/Normal:Almost everyone experiences occasional apnea, so less than 5 such events per hour are considered normal and no treatment is recommended.

Mild sleep apnea:CPAP is generally not recommended as a first choice for treating mild sleep apnea. Other interventions are generally recommended, such as weight loss, use of positional tricks (if sleep apnea occurs primarily when sleeping in the supine or supine position), improvements in sleep hygiene, and oral appliances (learn more about CPAP alternatives).Here).

Moderate and severe sleep apnea:CPAP therapy is generally recommended. Most insurance companies will authorize payment for CPAP if your AHI is moderate to severe (Learn How CPAP Therapy Works to Treat Sleep ApneaHere).

What do AHI, RERA, Arousal and RDI mean? (5)

(Video) Reading Sleep Study Results: Identifying Sleep Apnea

For a deeper dive into the terms and measurements found in sleep studies, download our guide to understanding sleep study results.

Download the guide


Other posts you might find interesting:

  • Which doctor should I talk to about my sleep problems?
  • How much will a sleep study cost?
  • The link between sleep apnea and diabetes
  • How does sleep apnea affect the heart?

What do AHI, RERA, Arousal and RDI mean? (6)

Julia Rodriguez

Julia joined Advanced Sleep Medicine Services, Inc. in 2011 with experience in sales, marketing and customer service. She is currently Vice President of Marketing and Operations and enjoys the opportunity to educate and interact with people who are looking to improve their health through better sleep.


  1. What do AHI, RERA, Arousal and RDI mean? (7)

    Jean Kruk Responder

    Posted on March 10, 2018

    I have recently started CPAP - (5 weeks) I have read the meaning of terms and abbreviations used I am interested in receiving a copy of the guide to understanding sleep study results - 2 pages, but I am unable to download it. I would appreciate it if you could email me a copy. Regards Jean

  2. What do AHI, RERA, Arousal and RDI mean? (8)

    Martinajef Responder

    Posted on 3/4/2018

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  3. What do AHI, RERA, Arousal and RDI mean? (9)

    Molly Min Mao Responder

    Posted on March 19, 2020

    Could you provide an updated link on the Medicare rule "50% reduction in airflow with 3% blood oxygen desaturation"? Because I only knew the rule of thumb for 30% airflow reduction at 4% desaturation. Thank you very much

    (Video) Obstructive Sleep Apnea Part 2: Definitions
  4. What do AHI, RERA, Arousal and RDI mean? (10)

    Himstra Responder

    Posted on 06.05.2020

    thanks for saving my life

  5. What do AHI, RERA, Arousal and RDI mean? (11)

    Lynn Jaffe Responder

    Posted on Aug 15, 2020

    I found this information very helpful; However, there is no hyperlink to download the manual, so it is not available.

  6. What do AHI, RERA, Arousal and RDI mean? (12)

    carol jackson Responder

    Posted on September 11, 2020

    I did a home sleep study and was diagnosed with mild sleep apnea. (AHI of 13.4). The study recommends therapeutic treatment with CPAP. Does Medicare need this second study? I thought it was separate from diagnostics and I just needed to determine the pressure setting on my machine.
    Thank you very much.

  7. What do AHI, RERA, Arousal and RDI mean? (13)

    fitness items Responder

    Posted on Aug 7, 2021

    (Video) Definition and Pictures of Sleep Apneas (Obstructive, Mixed, Central), Hypopnea, and RERAs

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    persimmon fruit Responder

    Posted on 09/03/2021

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  11. What do AHI, RERA, Arousal and RDI mean? (17)

    Mohamed bin El Ahab Responder

    Posted on November 11, 2021

    (Video) Scoring A Sleep Study: Uncut, Patient with RERAs, UARS

    I am interested in information about apnea

  12. What do AHI, RERA, Arousal and RDI mean? (18)

    DMZABO Responder

    Posted on January 16, 2022

    First, a very informative blog/post. Thank you for that. I've been on a Bi-Pap machine for over 3 years and it works fine. But if you want to take your sleep apnea knowledge to the next level, I recommend visiting SLEEPFILES.COM.
    Here it will download your nightly sleep information from the SD card residing in your sleep machine/device and show graphs of your most recent sleep to help you discuss it with your doctor. Known as OSCAR, it is ABSOLUTELY SAFE TO DOWNLOAD IT ON YOUR COMPUTER.
    AND IT'S FREE TO DOWNLOAD TOO. This is such useful information that you can use to potentially lower your AHI numbers and also help you comply with insurance company regulations.
    It has been helpful for me and I have been using it for about 2 weeks now and I really enjoy gaining knowledge on how to sleep better with sleep apnea. Most of the time, we'll do the sleep tests and find out if you're a candidate for sleep apnea therapy, and then the doctor will only see you once a year. This after the person who delivered your machine shows you how to proceed, and that's basically it. Well, using this app gives you the tools to help you find the right setup and equipment (leaks are a real problem). That is, it is very likely that you really know how to fight apnea and its side effects.

  13. What do AHI, RERA, Arousal and RDI mean? (19)

    Aster Perez Responder

    Posted on March 2, 2022

    It is the average number of combined apneas and hypopneas per hour. It is most commonly used to determine the severity of a person's sleep apnea.

  14. What do AHI, RERA, Arousal and RDI mean? (20)

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  15. What do AHI, RERA, Arousal and RDI mean? (21)

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    Posted on Oct 12, 2022

    (Video) Why Knowing Your AHI is NOT Enough

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leave a comment


1. Most doctors don't know about this - Upper airway resistance syndrome (UARS)
(Vik Veer - ENT Surgeon)
2. Sleep Nerds: Sleep Study Scoring of Central Apnea, Mixed Apnea, Hypopnea, and RERAs. Severe OSA
3. Sleep Study Scoring on Person with Normal Sleep. Polysomnograph
4. The Science of Orgasms
5. Airway Answers: Ep 7 - The Upper Airway Resistance with Ken Hooks
(Airway Circle)
6. WEBINAR: Reading a Sleep Test; So, That’s What Those Squiggly Lines Mean


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