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AHI Score Lookup

Enter your Apnea-Hypopnea Index to understand your severity classification, how it compares to the general population, and what the research says about treatment at your level.

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Find this number on your sleep study report, your CPAP machine screen, or by importing your SD card into CPAP Clarity.

What This Tool Does

This tool takes your Apnea-Hypopnea Index and returns three things: your AASM severity classification, how your AHI compares to the general adult population based on published prevalence data, and a summary of what clinical guidelines say about treatment options at your severity level. All processing happens in your browser. No data is sent to any server.

How AHI Is Measured

AHI is measured during a sleep study, either an in-lab polysomnography (PSG) or a home sleep apnea test (HSAT). During polysomnography, technicians monitor brain activity (EEG), airflow, chest and abdominal movement, blood oxygen levels, and other signals throughout the night. A trained sleep technologist then manually scores each respiratory event according to AASM criteria.

Home sleep tests use a simplified sensor set (typically nasal airflow, pulse oximetry, and chest effort) and calculate AHI using recording time rather than actual sleep time, since they cannot measure brain waves. This means HSAT-derived AHI can underestimate severity compared to PSG in some patients, because time spent awake during the recording is included in the denominator.

CPAP machines also report a nightly AHI using their built-in flow sensors. This "residual AHI" reflects how many events your machine detected while you were on therapy. It is useful for tracking treatment effectiveness night to night, but it is calculated using device-specific algorithms, not the same manual scoring criteria used in a sleep lab.

Severity Classification

The American Academy of Sleep Medicine (AASM) International Classification of Sleep Disorders, Third Edition (ICSD-3), defines four severity levels based on AHI:

  • Normal (AHI below 5): Fewer than 5 events per hour. Within the range seen in healthy adults without clinically significant sleep-disordered breathing.
  • Mild (AHI 5 to 14): 5 to 14 events per hour. May or may not produce noticeable symptoms. Treatment decisions at this level often depend on the presence of daytime sleepiness, cardiovascular risk factors, or occupational hazards.
  • Moderate (AHI 15 to 29): 15 to 29 events per hour. Associated with increased cardiovascular risk and more pronounced daytime symptoms. Treatment is generally recommended at this level.
  • Severe (AHI 30 or above): 30 or more events per hour. Strongly associated with significant oxygen desaturation, cardiovascular morbidity, and impaired daytime functioning. Treatment is considered essential.

These thresholds are consistent with the AASM ICSD-3 classification and are used by sleep labs and insurance companies worldwide.

AHI and Treatment Decisions

CPAP (continuous positive airway pressure) is the first-line treatment for moderate and severe obstructive sleep apnea. For mild cases, treatment guidelines are less prescriptive: CPAP is an option, but oral appliances (mandibular advancement devices), positional therapy (avoiding supine sleep), and weight management may also be appropriate depending on individual factors. Consider discussing the full range of options with your sleep provider.

Regardless of severity, weight loss has been shown to reduce AHI in patients who are overweight or obese. A 10% reduction in body weight is associated with a roughly 26% reduction in AHI (Peppard et al., 2000, JAMA). However, weight loss alone may not be sufficient for moderate or severe cases, and the benefit varies by individual anatomy. Your provider can help you evaluate which combination of therapies is most appropriate for your situation.

Frequently Asked Questions

What is AHI?

AHI stands for Apnea-Hypopnea Index. It is the number of apneas (complete airway blockages) and hypopneas (partial airway blockages) you experience per hour of sleep. A sleep study or your CPAP machine calculates this by dividing the total number of respiratory events by total sleep time (or recording time for home studies and CPAP devices). AHI is the primary metric used to diagnose sleep apnea severity and to evaluate whether treatment is effective.

What events are counted in AHI?

AHI counts two types of respiratory events. An apnea is a pause in airflow lasting at least 10 seconds. A hypopnea is a reduction in airflow of at least 30% lasting at least 10 seconds, accompanied by a 3% or greater drop in blood oxygen saturation or an arousal from sleep (per the AASM 2012 recommended scoring criteria). Some labs use an older 4% desaturation rule, which can produce a lower AHI for the same night of sleep. Obstructive, central, and mixed apneas are all included in the total count.

How does AHI change with CPAP treatment?

CPAP therapy typically reduces AHI significantly, often to below 5 events per hour when pressure is properly titrated. Your CPAP machine reports a residual AHI each night based on its flow sensor algorithms. This residual AHI is usually close to the value a sleep lab would measure, though the two are not identical because CPAP devices use proprietary detection algorithms rather than the EEG-based scoring used in polysomnography. A consistently elevated residual AHI may indicate that your pressure needs adjustment, your mask has a significant leak, or your sleep position is affecting therapy.

What is the difference between AHI and RDI?

AHI counts apneas and hypopneas only. RDI (Respiratory Disturbance Index) includes apneas, hypopneas, and respiratory effort-related arousals (RERAs). RERAs are brief arousals caused by increased breathing effort that do not meet the full criteria for an apnea or hypopnea. Because RDI includes more event types, it is always equal to or higher than AHI for the same night. Some insurance companies use RDI for CPAP qualification, which can help patients with upper airway resistance syndrome who have a low AHI but frequent RERAs.

Can AHI change over time without treatment changes?

Yes. Several factors can cause AHI to change over months or years. Weight gain tends to increase AHI because excess tissue around the airway narrows the pharyngeal space. Weight loss can reduce AHI, sometimes substantially. Aging, alcohol consumption, sedative medications, sleeping on your back, nasal congestion, and hormonal changes (such as menopause) can all influence AHI. Periodic re-evaluation with your sleep provider is worthwhile, especially if your symptoms change or you have gained or lost a significant amount of weight.

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