Mild, Moderate & Severe Sleep Apnea

In adults, obstructive sleep apnea severity is commonly described using the Apnea-Hypopnea Index (AHI). The conventional categories are:

• Normal: AHI below 5 events per hour
• Mild: AHI 5 to fewer than 15 events per hour
• Moderate: AHI 15 to fewer than 30 events per hour
• Severe: AHI 30 or more events per hour

These categories are based on how often breathing events (apneas and hypopneas) occur per hour of sleep. They provide a shared vocabulary for clinicians and patients. For details on what AHI counts and how it differs from related indexes, see the AHI, RDI & REI guide.

Important: These are adult classifications. They do not apply to children. See the section on pediatric considerations below.

The AHI categories describe event frequency — how often breathing pauses or reductions occur. They do not directly capture:

• Oxygen burden: How low oxygen drops and how long it stays low (see oxygen desaturation)
• Symptom burden: How sleepy, fatigued, or impaired the person feels during the day (see symptoms vs. AHI)
• Health history: Cardiovascular conditions, metabolic disorders, and other medical factors
• Event type: Whether events are obstructive, central, or mixed
• Position and stage effects: Whether events cluster in certain sleep positions or sleep stages

Because of this, two people with the same AHI category can have very different clinical pictures. The category is a starting point, not a complete summary.

The word "mild" describes event frequency, not impact. A person with mild OSA may still experience:

• Bothersome daytime sleepiness or fatigue
• Drowsy-driving concern, especially if symptoms impair alertness
• Significant oxygen dips despite a relatively low AHI
• Cardiovascular or metabolic conditions that increase the relevance of even mild OSA

Whether mild OSA warrants treatment is a clinical decision. Some people with mild OSA and no significant symptoms may be monitored, while others benefit from treatment. A healthcare provider weighs the AHI alongside symptoms, oxygen data, health history, and individual circumstances.

Safety note: If you experience drowsiness while driving, avoid driving when you feel unable to remain alert and discuss persistent daytime sleepiness with a healthcare professional.

People in the same severity category do not necessarily receive the same treatment. Treatment decisions may consider:

• Symptoms and daytime functioning
• Oxygen desaturation depth and duration
• Cardiovascular and metabolic health
• Ability to use a treatment consistently
• Anatomy and dental health
• Patient preferences and values

For a fuller discussion of these factors, see the treatment decision factors guide. The key point is that severity is one input, not a prescription.

The AHI cutoffs above are for adults. Children's sleep-disordered breathing uses different criteria, and even a small number of events can be more significant in a child. Symptoms and treatment approaches also differ.

If you are concerned about a child's breathing during sleep — including snoring, pauses, restless sleep, or behavioral concerns — a pediatric evaluation is recommended rather than applying adult categories. See our pediatric sleep apnea center for more information.