Sleep apnea is diagnosed through a sleep study that measures your breathing patterns, oxygen levels, and other body signals while you sleep. The process typically starts with a screening questionnaire at your doctor’s office, followed by either an at-home test or an overnight study in a sleep lab. Your results are scored using a standardized index, and a count of 5 or more breathing disruptions per hour generally confirms a diagnosis.
Screening: The First Step
Most diagnoses begin with a simple questionnaire. The two most common are the STOP-BANG and the Epworth Sleepiness Scale, and your doctor may use one or both.
The STOP-BANG asks eight yes-or-no questions covering snoring, daytime tiredness, whether anyone has observed you stop breathing, high blood pressure, BMI over 35, age over 50, neck circumference of 16 inches or more, and male sex. Each “yes” scores one point. A score of 3 or higher flags possible sleep apnea, though scores of 5 to 8 are much more specific, meaning fewer false alarms. The questionnaire is highly sensitive for moderate to severe cases, catching 93% to 100% of them in clinical studies.
The Epworth Sleepiness Scale takes a different angle. It scores how likely you are to doze off in eight everyday situations (watching TV, sitting in traffic, reading) on a scale of 0 to 24. Anything from 0 to 10 is considered normal daytime sleepiness. A score above 11 signals excessive sleepiness and usually triggers further testing. Neither questionnaire diagnoses sleep apnea on its own, but they help your doctor decide whether a sleep study is warranted.
Home Sleep Tests
If your screening suggests obstructive sleep apnea and you don’t have other complicating conditions (like heart failure or chronic lung disease), you’ll likely be offered an at-home test first. It’s simpler, cheaper, and lets you sleep in your own bed.
Home tests come in two main types. A Type 3 device measures airflow, breathing effort, blood oxygen levels, and heart rate. A Type 4 device measures only oxygen levels and heart rate. Type 3 tests give your doctor more data to work with and are more widely accepted for diagnosis. You typically pick up the device from a sleep clinic or receive it by mail, wear it for one or two nights, then return it so a sleep specialist can interpret the data.
Home tests cost between $150 and $1,000 before insurance, making them significantly more affordable than lab studies. The tradeoff is that they collect less information. They can’t measure brain waves, so they won’t detect how much time you spend in each sleep stage or pick up other sleep disorders like narcolepsy or periodic limb movement disorder. If a home test comes back normal but your symptoms are strong, your doctor will typically recommend a full lab study.
In-Lab Sleep Studies
An in-lab study, formally called polysomnography, is the most comprehensive diagnostic tool. You spend a night at a sleep center while a technologist monitors your brain waves, eye movements, heart rate, breathing pattern, blood oxygen level, body position, chest and abdominal movement, limb movement, and snoring. A small clip on your finger or ear tracks oxygen continuously, and sensors on your scalp record electrical brain activity.
It sounds like a lot of hardware, and it is. But the payoff is a complete picture of what happens while you sleep. In-lab studies are particularly important when your doctor suspects central sleep apnea (where the brain fails to send proper breathing signals), when a home test was inconclusive, or when other sleep disorders need to be ruled out. The average cost for an in-lab study is around $3,000, though it can range anywhere from $1,000 to $10,000 depending on your location and facility.
How Obstructive and Central Apnea Look Different
Both types of sleep apnea cause reduced or absent airflow through the nose and mouth, but the underlying mechanism is different, and the sleep study reveals which one you have. In obstructive sleep apnea, the airway physically collapses while your chest and abdominal muscles keep trying to breathe. The study shows continued respiratory effort against a closed airway. In central sleep apnea, there’s no respiratory effort at all because the brain temporarily stops sending the signal to breathe. This distinction matters because the two types require different treatment approaches.
Understanding Your Results: The AHI Score
Your sleep study results center on a number called the Apnea-Hypopnea Index, or AHI. This counts how many times per hour your breathing fully stops (apnea) or partially decreases (hypopnea) during sleep. Harvard Medical School classifies the severity as follows:
- Normal: fewer than 5 events per hour
- Mild: 5 to 14 events per hour
- Moderate: 15 to 29 events per hour
- Severe: 30 or more events per hour
These numbers directly affect your treatment options and insurance coverage. Medicare, for example, covers CPAP therapy if your AHI is 15 or higher. If your AHI falls between 5 and 14, Medicare still covers it, but only if you also have a related condition like high blood pressure, heart disease, or excessive daytime sleepiness. Many private insurers follow similar guidelines.
Diagnosis in Children
Children use a completely different severity scale because their baseline breathing rate and airway size differ from adults. An AHI of 1 or less is normal in pediatric patients. An AHI between 1 and 5 is considered very mildly elevated, 5 to 10 is mild, 10 to 20 is moderate, and above 20 is severe. In practical terms, an AHI above 5 clearly calls for treatment in a child, while an AHI below 3 typically doesn’t need intervention. The gray zone between 3 and 5 events per hour is judged case by case.
Children are almost always tested in a sleep lab rather than at home. Their sleep apnea often stems from enlarged tonsils or adenoids rather than the soft tissue collapse that causes most adult cases, and a full polysomnography helps the care team plan whether surgery, a dental device, or another approach makes the most sense.
What to Expect From Start to Finish
The timeline from first appointment to diagnosis usually runs two to six weeks. Your initial visit involves the screening questionnaire, a physical exam of your airway and neck, and a conversation about symptoms like snoring, gasping at night, morning headaches, and daytime fatigue. If your doctor orders a home test, you may have results within a week or two. An in-lab study requires scheduling an overnight appointment, which can take longer depending on availability at your local sleep center.
After the study, a board-certified sleep specialist reviews the raw data and generates a report with your AHI, oxygen dip patterns, sleep stage breakdown (for lab studies), and any other notable findings like leg movements or unusual heart rhythms. Your referring doctor then discusses the results and treatment options with you. If your study was done at home and the results were borderline or unclear, expect to be referred for a full in-lab study before a final diagnosis is made.