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Apnea-Hypopnea Index (AHI)

The Apnea-Hypopnea Index is a diagnostic metric used to evaluate the severity of sleep apnea. It represents the average number of apneas (complete pauses in breathing) and hypopneas (instances where partial obstructions cause shallow breathing) per hour of sleep. AHI is commonly calculated during a sleep study (polysomnogram) or home sleep apnea test. The index helps classify sleep apnea as mild, moderate, or severe and plays a critical role in determining whether interventions like CPAP therapy, oral appliances, or surgery may be called for.

Clinically, the Apnea-Hypopnea Index (AHI) offers an objective measure to correlate sleep-disordered breathing with symptoms such as daytime fatigue, impaired cognition, or cardiovascular risk. For physicians, understanding the AHI value in the context of patient history and comorbidities is essential for tailoring therapy.

Apnea-Hypopnea Index (AHI) Calculator

Apnea episodes

The patient is not breathing for at least 10 seconds

Hypopnea episodes

Abnormally slow or shallow breathing

Actual sleep time

Value

AHI Severity Chart

AHI Scoring & Interpretation

The Apnea-Hypopnea Index is calculated by dividing the total number of apneas and hypopneas by the number of hours of sleep. For example, if a patient experiences 80 respiratory events during 8 hours of sleep, their AHI is 10. This value is used to assess the severity of obstructive sleep apnea (OSA).

The severity thresholds for both adults and children were developed and standardized by the American Academy of Sleep Medicine (AASM) and are widely adopted in clinical practice and sleep laboratories. Interpretation should always consider clinical context, including symptoms, comorbidities, oxygen desaturation, and arousal indices.

Adult AHI Interpretation (Age ≥13 years)

• Normal: <5 events/hour
• Mild OSA: 5–14.9 events/hour
• Moderate OSA: 15–29.9 events/hour
• Severe OSA: ≥30 events/hour

These thresholds apply to adolescents and adults aged 13 and older. Adult scoring rules are recommended for patients ≥13 years of age, based on AASM guidelines.

Pediatric AHI Interpretation (Age <13 years)

• Normal: <1 event/hour
• Mild OSA: 1–4.9 events/hour
• Moderate OSA: 5–9.9 events/hour
• Severe OSA: ≥10 events/hour

In children under 13, even an AHI ≥1 is considered abnormal and may warrant further evaluation. Pediatric scoring criteria reflect children's increased sensitivity to disrupted sleep and associated developmental risks.

Learn more on the BackTable ENT Podcast

BackTable is a knowledge resource for physicians by physicians. Get practical advice on the Apnea-Hypopnea Index (AHI) and how to build your practice by listening to the BackTable Podcast.

Ep 210 Rethinking OSA: Role of the Nose with Dr. Keith Matheny and Dr. Ashwin Ananth

00:00 / 01:04

References

[1] American Academy of Sleep Medicine. The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications. Version 2.6. Darien, IL: American Academy of Sleep Medicine, 2020.
[2] Berry, R. B., Brooks, R., Gamaldo, C. E., Harding, S. M., Marcus, C. L., & Vaughn, B. V. "The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications." Journal of Clinical Sleep Medicine, 2012;8(5):597–619.
[3] Epstein, L. J., Kristo, D., Strollo, P. J., et al. "Clinical guideline for the evaluation, management and long-term care of obstructive sleep apnea in adults." Journal of Clinical Sleep Medicine, 2009;5(3):263–276.

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