AHI and RDI in Sleep Apnea: What Your Scores Really Mean

• Your AHI and RDI scores help determine the severity of sleep apnea.
• AHI measures apneas and hypopneas; RDI also includes subtle breathing disruptions.
• Daybreak helps you understand your results and get CPAP-free treatment at home.

The Apnea-Hypopnea Index (AHI) measures the average number of breathing disruptions you have per hour of sleep. It’s one of the main indicators used to diagnose sleep apnea.

• Apnea = a complete pause in breathing for at least 10 seconds
• Hypopnea = a partial reduction in airflow (typically by 30–50%) for at least 10 seconds, often accompanied by a drop in oxygen or an arousal from sleep

In other words, the higher the AHI, the more frequently your breathing is interrupted during sleep.

While AHI counts only apneas and hypopneas, the Respiratory Disturbance Index (RDI) includes additional breathing-related sleep disruptions called respiratory effort–related arousals (RERAs).

RERAs are events where breathing becomes labored enough to briefly wake you up, but not enough to meet the criteria for an apnea or hypopnea. These subtle disturbances can still fragment your sleep, cause daytime fatigue, and indicate upper airway resistance syndrome (UARS), a condition on the spectrum of sleep-disordered breathing.

So, while AHI focuses on oxygen drops, RDI gives a more complete picture by including arousals caused by breathing effort. This means your RDI is often slightly higher than your AHI, and in some cases, it can uncover sleep-disordered breathing that an AHI alone might miss.

Not all sleep studies are scored the same way. The main difference often comes down to how hypopneas (partial breathing reductions) are defined, specifically, how much your blood oxygen level must drop for the event to “count.”

There are two common scoring rules:

1. The 4% Rule
   1. A hypopnea is only counted if your oxygen level drops by 4% or more from baseline.
   2. This stricter definition tends to yield a lower AHI and can sometimes underestimate the severity of sleep apnea.
2. The 3% Rule
   1. A hypopnea is counted if your oxygen level drops by3% or more, or if it causes an arousal from sleep.
   2. This approach is more sensitive and captures events that still disrupt sleep quality even if oxygen drops are smaller.

Because of this difference, a patient might have:

• A higher AHI or RDI when scored using the 3% rule
• A lower AHI or RDI when scored using the 4% rule, potentially affecting insurance coverage or eligibility for treatment

This discrepancy underscores why understanding how your sleep test was scored is so important, and your medical insurance may require the 4% scoring technique (i.e. Medicare).

While AHI is the standard measure for diagnosing sleep apnea, RDI provides a broader view of sleep-disordered breathing. Two patients could have similar AHI scores but very different RDI scores, meaning one experiences far more sleep interruptions and daytime fatigue than the other.

Together, these metrics help physicians:

• Determine the presence and severity of OSA
• Identify milder forms of sleep disruption (like UARS)
• Tailor treatment options for better outcomes

AHI and RDI are two sides of the same coin, both critical for understanding how well you breathe during sleep. AHI counts apneas and hypopneas, while RDI gives a fuller picture by including subtle arousals. And depending on whether your test uses the 3% or 4% rule, your results, and your treatment path may differ.

If a sleep disorder is detected, Daybreak offers a custom-made, FDA-cleared oral appliance that gently repositions your jaw to keep your airway open at night. It’s a comfortable, effective, CPAP-free solution designed to help you breathe—and sleep—better.

Getting tested is the first step toward clarity. Understanding your results is the next step toward restful sleep, improved health, and renewed energy.

Wondering What Your AHI or RDI Score Means? Take the Daybreak At-Home Sleep Test to find out, it’s 98% accurate and doctor-reviewed.

1. Are RDI and AHI the same?

No, AHI and RDI are related but not identical. AHI measures apneas and hypopneas, while RDI includes those plus additional breathing disruptions known as RERAs (Respiratory Effort–Related Arousals), giving a more complete picture of sleep quality.

2. What is a normal AHI or RDI level in a sleep study?

A normal AHI or RDI is fewer than 5 events per hour. Scores between 5–14 indicate mild sleep apnea, 15–29 is moderate, and 30+ is considered severe.

3. What is moderate sleep apnea AHI?

Moderate sleep apnea is typically defined by an AHI score between 15 and 29. This means you’re experiencing 15–29 breathing disruptions per hour of sleep.

4. AHI vs RDI: Which is more important?

AHI is most used to diagnose sleep apnea, but RDI offers a broader view by including more subtle disturbances. Together, they help your provider understand the full impact on your sleep.

5. How do I test my AHI and RDI at home?

You can take an at-home sleep test with Daybreak. It’s easy, accurate, and reviewed by a doctor, no clinic visits or CPAP machines required.