STOP-BANG Score — OSA Screening Calculator
Screen for obstructive sleep apnea risk using the STOP-BANG questionnaire. 8 yes/no questions with risk stratification and predictive performance data.
AHI (Apnea-Hypopnea Index) Calculator
Calculate your Apnea-Hypopnea Index from sleep study data. Includes supine AHI, REM AHI, positional analysis, and severity grading.
⚠️ Medical Disclaimer: The AHI is one component of sleep apnea diagnosis. Clinical symptoms (EDS, witnessed apneas, morning headaches) and a formal sleep study are required for diagnosis.
Total Sleep Study Events
hrs
min
%
Positional Analysis
hrs
REM Analysis
hrs
Apnea-Hypopnea Index
15
Moderate OSA
Overall AHI⧉
15
105 events / 7 hrs — events per hour of sleep
Apnea Index⧉
6.4
Complete cessation of airflow for ≥10 seconds per hour
Hypopnea Index⧉
8.6
≥30% airflow reduction with ≥3% desat or arousal per hour
Supine AHI⧉
18.3
Not positionally dependent
Non-Supine AHI⧉
12.5
Events per hour in lateral/prone positions
REM AHI⧉
23.3
Not REM-dependent
SpO₂ Nadir⧉
82%
Hypoxic burden: Moderate
Total Sleep⧉
7 hrs
Total sleep time from PSG
AHI Severity Scale
| AHI Range | Severity | Clinical Significance |
|---|---|---|
| AHI < 5 | Normal | No clinically significant sleep apnea |
| AHI 5–14 | Mild | May cause daytime drowsiness; treatment discussions vary with symptoms and context |
| AHI 15–29 | Moderate | Significant sleep fragmentation; formal sleep-medicine review is common |
| AHI ≥ 30 | Severe | Higher cardiometabolic burden; management review is usually more urgent |
Typical Management Context by Severity
| Severity | Common Initial Discussion | Alternatives | CPAP Context |
|---|---|---|---|
| 5–14 (Mild) | Lifestyle, positional, and symptom-context review | Oral-appliance discussion when appropriate | Sometimes considered when symptoms or comorbidities are prominent |
| 15–29 (Moderate) | Formal treatment discussion is common | Alternative devices or procedures depend on anatomy and tolerance | Often part of the conversation |
| ≥30 (Severe) | Higher-acuity sleep-medicine management review | Adjunctive or alternative options depend on the full evaluation | Commonly discussed in this band |
Planning notes, formulas, and examples
About the AHI (Apnea-Hypopnea Index) Calculator
The AHI (Apnea-Hypopnea Index) Calculator computes your apnea-hypopnea index from sleep study data, providing severity classification, positional analysis (supine vs. non-supine), and REM-dependent analysis.
The AHI is the primary metric used to classify obstructive sleep apnea (OSA), the most common sleep-related breathing disorder affecting an estimated 936 million adults worldwide. It measures the number of complete airflow cessations (apneas) and partial reductions (hypopneas) per hour of sleep. Diagnosis still depends on the broader sleep-study and symptom context, not the number alone.
Beyond the overall AHI, it shows subgroup analyses that can change how the sleep-study report is interpreted. Positional OSA (supine AHI ≥2× non-supine AHI), REM-dependent OSA, and the SpO₂ nadir all add context beyond the headline AHI. The page keeps those values grouped so the report can be reviewed more coherently.
When This Page Helps
Sleep study reports often include multiple event counts, oxygen values, and subgroup analyses that are difficult to compare at a glance. This calculator keeps the core AHI context together with positional and REM-specific breakdowns so the same report can be reviewed more consistently and interpreted without losing the main sleep-study structure. It is useful when you need a concise summary of the study rather than a page of separate numbers.
How to Use the Inputs
- Enter the total number of apneas recorded during the sleep study.
- Enter the total number of hypopneas recorded.
- Enter total sleep time in hours and additional minutes.
- Enter the lowest SpO₂ recorded during the study.
- Select the study type (in-lab PSG or home sleep test).
- Optionally enter supine-specific event counts and time for positional analysis.
- Optionally enter REM-specific event counts and time for REM analysis.
- Review AHI severity, positional pattern, and the broader management context.
Formula used
AHI = (Total Apneas + Total Hypopneas) / Total Sleep Time (hours)
Apnea: Complete airflow cessation ≥10 seconds
Hypopnea: ≥30% airflow reduction with ≥3% SpO₂ desaturation or arousal under the commonly used AASM scoring approach
Supine AHI = Supine events / Supine time
Positional OSA: Supine AHI ≥ 2× Non-supine AHIExample Calculation
Result: AHI = 15.0 events/hr — Moderate OSA
With 105 total events over 7 hours, the AHI is 15.0, placing this patient in the moderate OSA category. The SpO₂ nadir of 82% indicates moderate hypoxic burden. In practice, this kind of result usually leads to a fuller sleep-medicine review rather than relying on the AHI alone.
Tips & Best Practices
- For accurate AHI, use total sleep time (not recording time) — PSG determines this precisely; home tests estimate it.
- AHI should be read together with symptoms, oxygen desaturation, and the broader sleep-study report rather than by itself.
- Always check both supine and non-supine AHI — half of OSA patients have positional disease.
- SpO₂ nadir below 80% is a cardiovascular risk factor independent of AHI.
- Residual AHI on CPAP should be <5 to consider treatment adequate.
Understanding Sleep Study Reports
A polysomnography report contains far more than the AHI alone. Key metrics include sleep efficiency, sleep staging distribution, periodic limb movement index, central vs. obstructive event classification, and oxygen desaturation index. The AHI remains the primary severity summary, but it is only one part of the full sleep-study interpretation.
Cardiovascular Impact of Untreated OSA
Untreated moderate-to-severe OSA is associated with a 2-3× increased risk of hypertension, 2-3× risk of atrial fibrillation, 1.5-2× risk of coronary artery disease, and 1.5-3× risk of stroke. The intermittent hypoxia–reoxygenation cycle causes oxidative stress, systemic inflammation, sympathetic activation, and endothelial dysfunction. Treatment with CPAP shows significant reduction in blood pressure and cardiovascular events.
Why Subgroup Patterns Matter
Positional disease, REM-predominant disease, and deep oxygen desaturations can make two patients with the same overall AHI look clinically different. That is why this page keeps the subgroup values visible instead of reducing the report to one number.
Sources & Methodology
Last updated:
Methodology
This page divides the total number of apneas and hypopneas by total sleep time to calculate AHI, then adds optional positional and REM-specific subgroup calculations when those inputs are available. It is built to summarize a sleep-study result, not to diagnose sleep apnea without the underlying study and symptom context.
The page keeps oxygen nadir, positional patterns, and REM patterns visible because the same overall AHI can have different clinical context depending on the rest of the sleep report. Treatment decisions still require clinician review of the full study.
Sources
- Hypopnea Scoring Alignment (American Academy of Sleep Medicine) — AASM position statement on the recommended hypopnea scoring criteria used in AHI calculation.
- Lung Health Basics: Sleep Fact Sheet (National Heart, Lung, and Blood Institute) — NHLBI overview of sleep apnea and sleep-related breathing context.
Frequently Asked Questions
AHI counts apneas and hypopneas per hour. RDI (Respiratory Disturbance Index) also includes RERAs (respiratory effort-related arousals), making it a more sensitive but less specific measure. AHI is the standard for OSA diagnosis.
CPAP is commonly part of the discussion for higher AHI bands, especially when symptoms, oxygen desaturation, or cardiometabolic comorbidity are present. The actual management plan still depends on the full sleep-study context and clinical history.
Home sleep tests (Type III) tend to underestimate AHI because they measure recording time rather than actual sleep time. A negative HSAT in a high-probability patient should be followed by in-lab PSG.
Positional OSA occurs when the supine AHI is at least twice the non-supine AHI. These patients may benefit from positional therapy (devices that prevent supine sleep) as standalone or adjunct treatment.
During REM sleep, skeletal muscle tone decreases (atonia), including pharyngeal dilator muscles, making the airway more collapsible. Some patients have OSA only during REM sleep.
Yes. Weight loss of 10-15% can reduce AHI by 50% in obese patients. Positional therapy, oral appliances, myofunctional therapy, and surgeries like UPPP or MMA can also reduce AHI.
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