Sleep health explainer
How to Read a Home Sleep Test Report: A Plain-English Guide
A home sleep apnea test report can look like a page of codes and percentages. This guide explains the main terms in an adult report so you can discuss the findings with your medical provider. Start with the signed interpretation, not just the largest number. The measurements support a diagnosis; they do not replace a review of your symptoms, medical history and test quality. [1]
1 Check what was measured
Find the test date, device name, usable recording duration and any comments about lost signals. A long recording is not necessarily a full night of usable data. If a sensor came off or you were awake for long stretches, tell your medical provider, even if the report looks complete. [2]
Look for whether the results are preliminary, automatically generated or reviewed. The American Academy of Sleep Medicine (AASM) advises against basing diagnosis or treatment decisions only on automatic scoring. Raw home-test data need qualified physician review and interpretation, with sleep-medicine expertise or oversight. [1]
2 Understand REI and AHI
Both numbers describe how often breathing events occur. Apneas are pauses or near-complete reductions in airflow; hypopneas are partial reductions that meet scoring rules. AHI means apnea-hypopnea index: the number of apneas and hypopneas per hour of sleep. REI means respiratory event index: events per hour of monitoring time in a typical home test. [1, 3]
Monitoring time is not automatically the entire recording. It should exclude unusable signal and identified awake periods, but it can still exceed actual sleep time. Most home tests do not measure brain waves to distinguish sleep from wake. A larger time denominator can make the event rate look lower. [1, 2]
For illustration, 60 events divided by six hours gives 10 events per hour; divided by four hours gives 15. This arithmetic is not a way to rescore your own test. Some devices estimate sleep and report AHI or pAHI, so ask what the label and denominator mean for your device. [2, 4]
3 Find the hypopnea scoring rule
A report may show results using a 3% rule, a 4% rule or both. In adults, the AASM-recommended hypopnea definition combines an airflow reduction of at least 30% for at least 10 seconds with either an oxygen-saturation drop of at least 3 percentage points or a brain-wave arousal. The alternative 4% definition requires the larger oxygen drop and does not count an arousal alone. [3]
These are drops from the preceding oxygen level, not absolute oxygen readings of 3% or 4%. Different scoring rules can produce different event rates from the same night. Most home tests cannot directly detect brain-wave arousals, so a home-test 3% result is not automatically equivalent to a lab result that also counts arousals. Compare like with like. [1, 3]
4 Read oxygen numbers together
ODI The oxygen desaturation index counts qualifying oxygen drops per hour. Check whether it uses a 3% or 4% drop and what time period is used in the calculation. ODI is not the same measurement as AHI or REI: it counts oxygen changes rather than scored breathing events. [5, 6]
Oxygen nadir This is the lowest recorded oxygen saturation, often labeled SpO2. It does not tell you how long the reading lasted. Movement or a poor sensor signal can create artifact, meaning an inaccurate measurement. Research on one home-test device found that automated nadir values sometimes required correction after review; that finding does not mean every low reading is false. Ask whether the low point was verified against the tracing. [7]
Time below a threshold Reports may list minutes or a percentage of time below 90%, sometimes called T90, or at another stated oxygen threshold. Read the units and the time denominator. Ten minutes and 10% are not interchangeable. Consider duration, overall pattern and signal quality alongside the nadir. A reporting threshold is not, by itself, a personal treatment or emergency cutoff. [6, 7]
5 Know what the result cannot settle
Home sleep apnea testing is intended for selected adults with suspected obstructive sleep apnea, not as a complete evaluation of every sleep problem. Significant heart or lung disease, suspected hypoventilation, chronic opioid use, stroke history or severe insomnia may make an in-lab study more appropriate. [8]
A negative result does not always rule out sleep apnea. The AASM diagnostic guideline recommends an in-lab sleep study, called polysomnography, after a single negative, inconclusive or technically inadequate home test. Review the next step with your medical provider, particularly if symptoms continue. Do not let a low headline number end the conversation. [8]
6 Bring these questions to your follow up
Was there enough reliable data? Does the event rate use monitoring time or measured or estimated sleep time? Which hypopnea rule was used? Were the oxygen findings verified? Do the results explain my symptoms, and is another evaluation needed? Write down the answers beside your report so you leave knowing what the findings mean for you.
The main point Read the interpretation, event rate, oxygen pattern and technical limitations together. Let your medical provider connect those findings to your health and explain the plan. Do not start or change treatment from a report number alone.
Educational information for adults, not a diagnosis or an individualized treatment plan.
Sources and further reading
Primary research and professional guidance supporting this article. Sources checked October 2026.
- Rosen and colleagues. AASM position statement on home sleep apnea testing. 2018.
Test interpretation, REI versus AHI, arousal limitations and the role of medical providers.
- Zhao and colleagues. Effect of manual editing of total recording time. 2017.
Primary study of recording-time editing, wakefulness and underestimation of event rates.
- Malhotra and colleagues. AASM position statement on arousal-based scoring. 2018.
Adult hypopnea definitions and the differences between 3% or arousal and 4% criteria.
- AASM Scoring Manual Version 3 frequently asked questions.
Home-test report terminology, REI and peripheral arterial tonometry indices.
- Whenn and colleagues. Study type and sleep measurement in ODI calculation. 2024.
Primary research showing that ODI depends on the time denominator and wake handling.
- American Thoracic Society. Interpreting sleep studies primer.
Report examples distinguish oxygen nadir, desaturation index and time below oxygen thresholds.
- Plante and Rumble. Watch for and correct oximetry artifact. 2023.
Single-center primary study of WatchPAT oxygen-nadir errors; not a universal device error estimate.
- Kapur and colleagues. AASM guideline for adult OSA diagnostic testing. 2017.
Patient selection and polysomnography after negative, inconclusive or inadequate home testing.