Sleep Study Report: What Your AHI Score Means for Snoring
The AHI on a sleep study counts breathing pauses and partial drops per hour of sleep, and that number sets the severity band. If a home test is negative, inconclusive or technically inadequate, the sleep guideline calls for a lab study next.
At a glance
- AHI: apnoeas and hypopnoeas counted per hour of sleep, where an apnoea is a full pause and a hypopnoea is a partial drop in airflow.
- Bands: below 5 is usually read as normal, 5 to 15 is mild, above 15 to 30 is moderate, and above 30 is severe.
- Home tests: many divide by recording time rather than sleep time, so the number can read lower than a lab study.
- Rule of thumb: the AHI shows how often breathing events happen, and a negative home test does not settle the matter while symptoms continue.
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What does AHI mean on a sleep study?
AHI stands for apnoea-hypopnoea index. An apnoea is a full pause in breathing, and a hypopnoea is a partial drop in airflow. The index adds up both kinds of event and divides by the hours of sleep, so an AHI of 10 means ten events an hour on average. A 2021 review in the journal Sleep describes the AHI as the frequency of apnoeas and hypopnoeas during sleep.
What are the AHI severity bands?
The mild, moderate and severe bands below are the 1999 American Academy of Sleep Medicine grades, which the 2021 review says the 2012 update did not change. The normal line below 5 is not one of those grades; the review traces it to a threshold from healthy-control studies. Treat all of the bands as a guide rather than a fixed line.
| Band | AHI, events per hour |
|---|---|
| Normal | Below 5 |
| Mild | 5 to 15 |
| Moderate | Above 15 to 30 |
| Severe | Above 30 |
Ask the lab which convention it uses for a value that falls exactly on a boundary, since a number on the edge can be grouped differently in different reports.
Why can a home test give a lower number?
Many home sleep apnoea tests divide the events by the time the device was recording, rather than by the time you were actually asleep. The recording time is usually longer than the sleep time, so the result can come out lower than a lab study’s AHI. The 2021 review makes that gap explicit, and the American Academy of Sleep Medicine has proposed a separate term, the respiratory event index, to tell home-test values apart from lab values.
When does the guideline call for a lab study?
The 2017 American Academy of Sleep Medicine guideline on diagnostic testing for adult sleep apnoea says that if a single home test is negative, inconclusive or technically inadequate, a polysomnogram, which is a full lab study, should be done. It also prefers the lab study for people with significant heart or lung disease, possible respiratory muscle weakness from a neuromuscular condition, awake low breathing, chronic opioid medication use, a history of stroke, or severe insomnia.
Can a sleep questionnaire diagnose apnoea on its own?
No. The same guideline recommends that clinical tools, questionnaires and prediction algorithms not be used to diagnose adults with sleep apnoea without a polysomnogram or a home test. A questionnaire can raise the question, but a sleep test is what answers it.
What should you ask about your sleep study report?
- Confirm the test type. Ask whether it was a full lab study or a home test, because the two numbers are not directly comparable.
- Find the AHI and its band. Write down the AHI value and the severity word the report uses.
- Ask about position and REM sleep. Ask whether the AHI is also given for back sleeping and for REM sleep, since the sleep clinic can use that split.
- Ask for the next step. Ask what the sleep clinician plans to do, and when you will hear the decision.
Insider tip: ask for the split
A single AHI can hide a pattern. Ask whether the report shows the AHI for back and side sleeping separately, and for REM and non-REM sleep. If the numbers differ a lot, raise that with the sleep clinician before you accept the overall score. Confirm with your clinic whether they report these splits at all.
If you snore, the snoring fixes guide covers side sleeping and the test choice in more detail, and the snoring and sleep apnoea guide covers the weight link. The signs a partner or family member can watch for are in the sleep apnoea checklist. The rest of the printouts are in the Lab Reports Decoded hub.
Get medical help soon if a partner notices pauses in your breathing, if daytime sleepiness affects your driving, or if you have morning headaches, or chest pain or breathlessness at night. Anyone with heart or lung disease, a history of stroke, or long-term opioid use should talk to the sleep team before accepting a home test. Treatment choices belong to the sleep clinician, and no sleep aid should be started or stopped on your own.
Sleep study questions, answered
What is a normal AHI score?
An AHI below 5 events per hour is usually read as normal. The 2021 review traces that figure to a threshold from healthy-control studies rather than to the severity grades, and the bands are guides rather than fixed lines.
Is an AHI of 15 severe?
No. Under the printed bands, 5 to 15 is mild, and moderate starts above 15 and runs up to 30. Ask the lab which convention it uses for a value that falls exactly on a boundary.
Is a home sleep apnoea test as accurate as a lab study?
Not always. A home test can read lower than a lab study, and the 2017 guideline sends a negative, inconclusive or technically inadequate home test on to a polysomnogram.
What is the difference between polysomnography and a home sleep test?
Polysomnography is the full lab study, and a home test is a shorter recording done at home. The guideline asks for a lab study when a home result is negative, unclear or technically poor.
Can a sleep questionnaire diagnose apnoea?
No, not on its own. The guideline asks for a sleep test before an adult is diagnosed with sleep apnoea.
Does snoring always mean sleep apnoea?
Not always. Snoring alone does not produce an AHI, so the sleep test decides the severity band rather than how loud the snoring sounds.
Can the report show whether I sleep on my back?
It may. Ask whether the AHI is given for back and side sleeping, and whether REM sleep is shown separately, since not every report includes these splits.
My sleep study looks normal, but I still feel tired. What now?
Tell the sleep clinician. If the result came from a home test, the guideline points to a lab study, and if it came from a lab study, bring the symptoms back to the clinician for review.