A patient-friendly guide to understanding your sleep study results — what the numbers mean and how they affect your treatment options.
Quick Answer
Your sleep study results include the apnea-hypopnea index (AHI) — the average number of breathing events per hour — and your oxygen saturation nadir. An AHI below 5 is normal, 5–14 is mild, 15–29 is moderate, and 30+ is severe sleep apnea. These numbers, along with oxygen data, guide your diagnosis and treatment plan.
Key Takeaways
After your sleep study, the recorded data is analyzed by a physician who generates a detailed report. This report contains several key measurements that determine whether you have sleep apnea, how severe it is, and which treatment options are appropriate for you.
The most important number in your results is the apnea-hypopnea index (AHI). This is the average number of times per hour that your breathing completely stops (apnea) or becomes significantly reduced (hypopnea) during sleep. The AHI is the primary metric used to diagnose sleep apnea and classify its severity.
In addition to the AHI, your report will include your oxygen saturation nadir (the lowest oxygen level recorded during the night), the percentage of time your oxygen was below 90%, heart rate data, and — if you had an in-lab study — information about your sleep stages and sleep efficiency.
The AHI is calculated by dividing the total number of apneas and hypopneas by the total number of hours of sleep. For example, if you had 60 breathing events during 6 hours of sleep, your AHI would be 10, which falls in the mild range.
Here is how AHI scores are classified:
Normal (AHI < 5)
Fewer than 5 breathing events per hour. No sleep apnea diagnosis.
Mild (AHI 5–14)
5 to 14 breathing events per hour. Treatment may be recommended, especially if symptoms are present. Oral appliance therapy is often an excellent option.
Moderate (AHI 15–29)
15 to 29 breathing events per hour. Treatment is typically recommended. Oral appliance therapy or CPAP may be appropriate.
Severe (AHI 30+)
30 or more breathing events per hour. Treatment is strongly recommended. CPAP is typically first-line, but oral appliance therapy may be an option for CPAP-intolerant patients.
During sleep apnea events, breathing pauses or reduces, which can cause oxygen levels in the blood to drop. Your sleep study report includes several oxygen-related measurements:
Oxygen levels below 90% during sleep are considered significant. Frequent or prolonged drops can strain the cardiovascular system and contribute to high blood pressure, heart disease, and other health problems. Your provider considers both AHI and oxygen data when recommending treatment.
If you had an in-lab polysomnography, your report will include information about your sleep architecture — the distribution of time spent in each sleep stage. Sleep is divided into two main types: non-REM sleep (which has three stages) and REM sleep.
N1 (Light Sleep)
The transition from wakefulness to sleep. Typically makes up about 5% of total sleep time.
N2 (Light Sleep)
A deeper stage of light sleep. Makes up about 45–50% of total sleep time.
N3 (Deep Sleep)
The most restorative sleep stage. Important for physical recovery, immune function, and hormone regulation. Makes up about 15–25% of total sleep time.
REM Sleep
Rapid eye movement sleep, associated with dreaming, memory consolidation, and emotional processing. Makes up about 20–25% of total sleep time.
Sleep apnea disrupts the normal cycling through these stages. Patients with sleep apnea often spend less time in deep sleep and REM sleep, which contributes to daytime fatigue, difficulty concentrating, and other symptoms. Treatment helps restore normal sleep architecture.
Home sleep tests do not measure sleep stages because they do not monitor brain waves. This is one of the key differences between home testing and in-lab polysomnography. Learn more at our sleep study vs home sleep test comparison page.
The severity of your sleep apnea — determined by your AHI — plays an important role in treatment planning. Here is what each severity level typically means for patients:
Mild Sleep Apnea (AHI 5–14)
You experience 5 to 14 breathing events per hour. Symptoms may include snoring and mild daytime fatigue. Treatment may be recommended if symptoms are bothersome or if you have other risk factors. Oral appliance therapy is often the preferred treatment for mild OSA.
Moderate Sleep Apnea (AHI 15–29)
You experience 15 to 29 breathing events per hour. Symptoms are typically more noticeable and may include significant daytime sleepiness, morning headaches, and impaired concentration. Treatment is generally recommended. Both CPAP and oral appliance therapy are appropriate options.
Severe Sleep Apnea (AHI 30+)
You experience 30 or more breathing events per hour — meaning your breathing pauses or reduces every 2 minutes or more frequently. Symptoms are usually significant, and health risks are elevated. CPAP is typically the first-line treatment, but oral appliance therapy may be recommended for patients who cannot tolerate CPAP. Learn about CPAP alternatives.
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A low AHI means your sleep apnea is not a health concern.
Even mild sleep apnea (AHI 5–14) can cause significant symptoms and increase health risks over time. Treatment may be recommended based on symptoms and overall health, not AHI alone.
If your oxygen levels are normal, you don't have sleep apnea.
Some patients with sleep apnea maintain normal oxygen levels but still experience frequent breathing events. AHI is the primary diagnostic metric, not oxygen alone.
Sleep study results are too complicated for patients to understand.
The key metrics — AHI and oxygen levels — are straightforward. Your provider will explain your results in plain language and help you understand what they mean for your health.
Severe sleep apnea means CPAP is your only option.
While CPAP is typically first-line for severe OSA, patients who cannot tolerate CPAP may be candidates for oral appliance therapy. Treatment is personalized based on severity, lifestyle, and preferences.
If your sleep study results show any level of sleep apnea, discuss treatment options with your provider. Even mild sleep apnea can worsen over time and increase health risks if left untreated. If you experience chest pain, severe shortness of breath, fainting, or irregular heartbeats, seek immediate medical attention.
Learn About Your Treatment Options
Understanding your diagnosis is the first step toward better sleep. Explore educational resources on sleep apnea treatment options, including CPAP alternatives and oral appliance therapy.
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Sleep Apnea and Heart Disease
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Symptoms such as loud snoring, witnessed breathing pauses, excessive daytime fatigue, and morning headaches may indicate obstructive sleep apnea. If you experience these symptoms regularly, a professional sleep evaluation is recommended.
Seek immediate medical attention if you experience chest pain, severe shortness of breath, fainting, or any symptoms that feel life-threatening. These may indicate a medical emergency requiring urgent care.
Untreated sleep apnea is associated with elevated risk of high blood pressure, heart disease, stroke, and type 2 diabetes. Do not ignore persistent symptoms — early evaluation and treatment can help protect your long-term health.
This page is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider regarding your individual health concerns.