From the Guidelines
The Apnea-Hypopnea Index (AHI) levels for classifying obstructive sleep apnea are: mild OSA is defined as an AHI of 5 to less than 15 events per hour, moderate OSA is an AHI of 15 to less than 30 events per hour, and severe OSA is an AHI of 30 or more events per hour. These classifications help clinicians determine the severity of a patient's condition and guide appropriate treatment decisions, as indicated in the 2024 European Heart Journal guidelines 1. The AHI represents the average number of apneas (complete breathing pauses) and hypopneas (partial breathing reductions) that occur per hour of sleep.
Key points to consider when evaluating AHI levels include:
- A normal AHI is generally considered to be fewer than 5 events per hour
- Higher AHI values indicate more frequent breathing disruptions during sleep and are associated with greater risk of cardiovascular complications, daytime sleepiness, cognitive impairment, and reduced quality of life
- The severity of OSA is directly correlated with AHI levels, with mild OSA having an AHI of 5 to less than 15, moderate OSA having an AHI of 15 to less than 30, and severe OSA having an AHI of 30 or more events per hour, as defined in the 2024 guidelines 1.
In contrast to older studies, such as the 2008 Journal of Clinical Sleep Medicine guidelines 1, which defined mild, moderate, and severe OSA according to the respiratory disturbance index (RDI), the 2024 European Heart Journal guidelines 1 provide a more recent and widely accepted definition of OSA severity based on AHI levels. Therefore, the 2024 guidelines should be used to guide clinical decision-making regarding OSA diagnosis and treatment.
From the Research
AHI Levels for Obstructive Sleep Apnea
The Apnea-Hypopnea Index (AHI) is used to estimate the severity of obstructive sleep apnea (OSA). According to the studies, the AHI levels for mild, moderate, and severe OSA are:
Limitations of AHI
While AHI is widely used to assess OSA severity, it has limitations. For example, it does not provide information on the severity of individual obstruction events 3. Alternative metrics, such as hypoxic burden, arousal intensity, and cardiopulmonary coupling, may provide additional information on OSA severity 4, 5.
Outcome Measurements in OSA
Outcome measurements in OSA should not be limited to AHI alone. Other measures, such as general quality of life, OSA-specific quality of life, measurements of sleepiness, and physiological measures, can provide a more comprehensive assessment of OSA severity and treatment outcomes 6.