What is AHI? Sleep apnea severity explained
4 min read · Reviewed 2026-10-06
Short answer
AHI (Apnea-Hypopnea Index) is the average number of times per hour your breathing stops or becomes very shallow during sleep, measured by a sleep study. In adults, under 5 is generally considered normal, 5–14.9 mild, 15–29.9 moderate, and 30 or more severe obstructive sleep apnea.
Apneas and hypopneas
An apnea is a pause in breathing lasting at least 10 seconds. A hypopnea is a partial reduction in airflow, usually with a drop in oxygen or a brief awakening. AHI counts both and divides by hours of sleep (or recording time on a home test).
Adult AHI ranges
- Less than 5: No obstructive sleep apnea
- 5 to 14.9: Mild
- 15 to 29.9: Moderate
- 30 or more: Severe
Why a screening score isn't an AHI
A questionnaire like STOP-Bang estimates risk; it doesn't count breathing events. Severity can only be measured with a sleep study and is interpreted by a clinician alongside your symptoms and health history.
Sources
- American Academy of Sleep Medicine — Obstructive sleep apnea — sleepeducation.org
- Kapur VK, et al., Journal of Clinical Sleep Medicine (AASM guideline) — Clinical Practice Guideline for Diagnostic Testing for Adult Obstructive Sleep Apnea (2017)
This article is general education, not medical advice. Talk with a clinician about your situation.