From the Guidelines
The severity of sleep apnea is determined by the Apnea-Hypopnea Index (AHI), which measures the number of breathing interruptions per hour during sleep, with mild sleep apnea diagnosed with an AHI of 5-14.9 events per hour, moderate sleep apnea with an AHI of 15-29.9 events per hour, and severe sleep apnea with an AHI of 30 or more events per hour, as confirmed by the most recent guidelines 1.
Severity Classification
The AHI score is used to classify the severity of sleep apnea, with the following categories:
- Mild sleep apnea: AHI of 5-14.9 events per hour
- Moderate sleep apnea: AHI of 15-29.9 events per hour
- Severe sleep apnea: AHI of 30 or more events per hour This classification is supported by recent studies, including a systematic review and meta-analysis published in 2022 1, and is consistent with the 2024 ESC guidelines for the management of elevated blood pressure and hypertension 1.
Importance of Severity Assessment
Proper severity assessment is essential because untreated severe sleep apnea increases risks of cardiovascular problems, metabolic disorders, and neurocognitive impairment. The severity score guides treatment decisions, ranging from lifestyle modifications for mild cases to continuous positive airway pressure (CPAP) therapy or even surgical interventions for severe cases. In addition to the AHI, oxygen desaturation levels are often considered when assessing severity, with significant drops in blood oxygen levels indicating more serious disease.
From the Research
Severity Score for Sleep Apnea
The severity of sleep apnea is typically measured by the apnea-hypopnea index (AHI), which is the number of apnea and hypopnea events per hour of sleep 2.
Apnea-Hypopnea Index (AHI)
- The AHI is a well-established metric for assessing sleep apnea severity, although it has limitations 2.
- A greater AHI is associated with increased severity of sleep apnea and poorer treatment outcomes 3.
- The AHI is used to classify sleep apnea into different severity levels, including mild, moderate, and severe 3.
Classification of Sleep Apnea Severity
- Mild sleep apnea: AHI of 5-14 events per hour 3.
- Moderate sleep apnea: AHI of 15-29 events per hour 3.
- Severe sleep apnea: AHI of 30 or more events per hour 3.
Alternative Metrics for Sleep Apnea Severity
- Hypoxic burden, arousal intensity, odds ratio product, and cardiopulmonary coupling are alternative metrics that may be used to assess sleep apnea severity 2.
- Composite indices of sleep apnea severity, such as the Sleep Apnea Severity Index and Modified Sleep Apnea Severity Index, may be more robust measures of disease burden than AHI alone 4.