Sleep apnea testing usually involves either an overnight study at a sleep lab or a portable device you wear at home. Which one you get depends on your symptoms, risk factors, and what your doctor suspects. The process typically starts with a screening questionnaire and physical exam, then moves to one of these two monitoring methods that track your breathing, oxygen levels, and other body signals while you sleep.
Screening Before the Sleep Study
Before anyone hooks you up to sensors, your doctor will assess your risk level. The most widely used screening tool is the STOP-Bang questionnaire, an eight-question checklist that covers snoring, tiredness, observed pauses in breathing, high blood pressure, body mass index, age, neck circumference, and gender. Each “yes” answer scores one point. A score of 0 to 2 puts you at low risk, 3 to 4 at intermediate risk, and 5 or higher at high risk for obstructive sleep apnea.
Your doctor will also look inside your mouth. They’re checking how crowded your airway is using a grading system that ranges from a wide-open view of the back of your throat (low risk) to being able to see only the hard palate at the roof of your mouth (high risk). A crowded airway, a large neck circumference, or enlarged tonsils can all point toward a breathing problem during sleep. If the screening suggests moderate or high risk, you’ll be referred for a formal sleep study.
In-Lab Polysomnography
A polysomnography, or PSG, is the most comprehensive sleep test available. You spend a night at a sleep center, usually arriving in the evening and leaving the next morning. A technologist places sensors on your scalp, temples, chest, and legs using mild adhesive, and clips a small monitor onto your finger or ear to track blood oxygen levels. All of these sensors connect by wire to a computer in another room.
While you sleep, the system records your brain waves, eye movements, heart rate, breathing pattern, blood oxygen level, body position, chest and belly movement, limb movement, and any snoring. Brain wave monitoring (EEG) lets the technologist see exactly when you fall asleep, how long you spend in each sleep stage, and whether your sleep is being disrupted by breathing pauses. A technologist watches your data in real time throughout the night, so if something unusual happens, they see it immediately.
In-lab studies are typically recommended when your doctor suspects something beyond straightforward obstructive sleep apnea, such as central sleep apnea, periodic limb movements, or narcolepsy. They’re also used when you have significant heart or lung conditions that need closer monitoring overnight.
Home Sleep Apnea Testing
For most people with a straightforward suspicion of obstructive sleep apnea, a home test is the simpler and more common option. Your sleep clinic sends you home with a small portable device that you set up yourself before bed. The standard setup measures at least four signals: airflow through your nose (via a small nasal sensor), breathing effort (using a flexible band around your chest or abdomen), blood oxygen saturation, and heart rate through a finger clip.
Some newer devices add a body position sensor and a microphone to detect snoring. There are also models that use a finger probe to measure changes in your pulse wave volume, which can detect the subtle cardiovascular responses that happen each time your airway closes. The most minimal versions use a single sensor placed on the throat that captures airflow, breathing effort, and snoring all at once.
Home tests are less detailed than in-lab studies. They don’t monitor brain waves, so they can’t tell exactly when you’re asleep versus lying awake. This means they can underestimate the severity of your condition, since time spent awake gets counted as sleep time in the final calculations. If your home test comes back normal but your symptoms are still significant, your doctor may follow up with a full in-lab study.
How to Prepare for Your Test
The preparation is the same whether you’re testing at home or in a lab. Avoid caffeine and alcohol for at least eight hours before the study. Don’t nap that day, since a nap can make it harder to fall asleep during the test. Shower or bathe beforehand, but skip lotions, creams, hair gel, and hairspray afterward. Clean skin and hair help the adhesive sensors stick properly and get clear readings.
For an in-lab study, pack what you’d normally bring for an overnight stay: pajamas, a toothbrush, something to read. Most sleep centers have private rooms set up to feel more like a hotel than a hospital. The sensors feel unusual but they shouldn’t be painful, and most people manage to fall asleep despite them.
What Your Results Mean
The main number your doctor looks at is the Apnea-Hypopnea Index, or AHI. This counts how many times per hour your breathing partially or completely stops during sleep. The severity scale for adults breaks down like this:
- Normal: fewer than 5 events per hour
- Mild: 5 to fewer than 15 events per hour
- Moderate: 15 to fewer than 30 events per hour
- Severe: 30 or more events per hour
For children, the thresholds are much lower. An AHI of 1 or above is considered abnormal, with mild ranging from 1 to fewer than 5 events per hour, moderate from 5 to fewer than 10, and severe at 10 or more. A child with an AHI of 6 would be classified as moderate, while the same number in an adult would be mild.
Your report will also include the Oxygen Desaturation Index, which tracks how often your blood oxygen drops by 3% or more for at least 10 seconds. This gives your doctor a picture of how much your body is being starved of oxygen during the night, which matters for understanding cardiovascular risk and guiding treatment decisions. Low oxygen episodes that happen dozens of times per hour put significant strain on the heart over time.
Testing for Other Sleep Disorders
If your overnight study suggests excessive daytime sleepiness that doesn’t match a breathing problem, your doctor may order a Multiple Sleep Latency Test the following day. This test measures how quickly you fall asleep during the daytime and whether you enter dream sleep abnormally fast. You take five scheduled naps, each two hours apart, in the same sleep lab. Each nap opportunity lasts up to 20 minutes. If you fall asleep, the test continues for another 15 minutes to see whether you slip into REM sleep.
Falling asleep in an average of 8 minutes or less across the five naps, combined with entering REM sleep during two or more of them, is the pattern that points toward narcolepsy. This test is always done the morning after an in-lab polysomnography, since your doctor needs the overnight data to rule out sleep apnea or other conditions that could be fragmenting your sleep and making you excessively tired during the day.