Apnea Hypopnea Index (AHI)

Last Updated: January 6, 2019

Definition - What does Apnea Hypopnea Index (AHI) mean?

The sleep hypopnea index (AHI) is used as a clinical diagnostic tool to determine if a patient has sleep apnea and to what severity. It is the sum of the number of apneas and hypopneas recorded during a patient's sleep study divided by the number of hours. By comparing this number against a diagnostic chart, a doctor can see if a patient falls into the clinical definition of sleep apnea and to what severity.

WorkplaceTesting explains Apnea Hypopnea Index (AHI)

The sleep hypopnea index (AHI) is calculated based on the number of apneas and hypopneas a patient suffers during a sleep study and the duration of the study. An apnea is when a person stops breathing for 10 seconds or more with no air or oxygen flowing into the lungs. During hypopnea the person does breathe but the amount of air or oxygen is severely limited.

After the sleep study when the measurement of apenas and hypopneas is taken, the research staff will take the total number events and divide that by the total hours slept. The result is a number of events per hour. Those with a result of less than five per hour are considered to have minimal interruptions. A number of six through 15 falls into the clinical diagnosis of mild sleep apnea and those with 16 through 30 per hour are diagnosed as having moderate sleep apnea. Anyone having over 30 incidents per hour is considered to have severe sleep apnea.


Persons who are in the moderate to high range are often encouraged to use a device such as a CPAP or APAP machine during sleep to help keep steady airflow and reduce the number of apea and hypopnea events during sleep.

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