Sleep apnea diagnosis typically starts with a screening questionnaire and physical exam, then moves to an overnight sleep study that measures how many times your breathing stops or slows each hour. The process can happen in a sleep lab or, for many adults, at home with a portable device. Here’s what to expect at each step.
Screening Questionnaires and Initial Assessment
Before ordering any testing, your doctor will assess your risk using standardized tools. The most widely used is the STOP-BANG questionnaire, an eight-question yes/no checklist that covers snoring, daytime tiredness, observed pauses in breathing, high blood pressure, BMI, age, neck circumference, and male sex. A score of 0 to 2 puts you in the low-risk category for moderate to severe obstructive sleep apnea. A score of 3 or 4 is intermediate risk, and 5 to 8 is high risk.
You may also be asked to fill out the Epworth Sleepiness Scale, which rates how likely you are to doze off in eight everyday situations like sitting in traffic or watching TV. Scores range from 0 to 24, with anything 11 or above pointing to abnormal daytime sleepiness. Neither of these tools diagnoses sleep apnea on its own, but together they help your doctor decide how urgently you need a sleep study and what type makes sense.
What Happens During the Physical Exam
Your doctor will look at several physical features that raise the odds of airway obstruction during sleep. One key measurement is neck circumference: greater than 17 inches in men or 16 inches in women is a recognized risk factor. A larger neck often means more soft tissue that can collapse into the airway when throat muscles relax at night.
You’ll likely be asked to open your mouth wide so the doctor can evaluate your airway using the Mallampati classification. This four-class scale rates how much of the back of your throat is visible. In Class I, the soft palate, uvula, and surrounding structures are all clearly seen. By Class IV, only the hard palate (the bony roof of your mouth) is visible, meaning the airway opening is significantly crowded. Higher Mallampati scores are associated with increased odds of obstructive sleep apnea. Your doctor will also check for enlarged tonsils, a recessed jaw, nasal congestion, and signs of conditions that commonly travel with sleep apnea, like high blood pressure or obesity.
In-Lab Polysomnography
The gold standard for diagnosing sleep apnea is an overnight polysomnography, or PSG, conducted in a sleep lab. You arrive in the evening, and a technician attaches sensors to your scalp, face, chest, abdomen, and legs. These sensors track brain wave activity, eye movements, muscle tone, heart rhythm, airflow through your nose and mouth, blood oxygen levels, and the rise and fall of your chest and abdomen as you breathe. A small clip on your finger continuously monitors oxygen saturation throughout the night.
The test isn’t painful, though the wires take some getting used to. Most people do manage to sleep enough for the study to be scored. A sleep technician monitors your data in real time from another room. In a “split-night” study, if severe apnea is detected in the first half of the night, the technician may wake you to fit a CPAP mask so the second half can be used to calibrate your treatment pressure.
In-lab testing is preferred when your doctor suspects something beyond straightforward obstructive sleep apnea, such as central sleep apnea, a seizure disorder, or significant heart or lung disease. It’s also the go-to option for children.
Home Sleep Apnea Testing
For adults who show signs of moderate to severe obstructive sleep apnea and don’t have complicating medical conditions, a home sleep apnea test (HSAT) is a simpler alternative. You pick up a portable device from your doctor’s office or a sleep center, strap it on at bedtime in your own bed, and return it the next day. Home devices are smaller than lab setups. They typically track airflow, breathing effort, and blood oxygen, but they don’t record brain waves, so they can’t measure sleep stages or detect other sleep disorders.
A few important rules govern these tests. The American Academy of Sleep Medicine requires that an HSAT be ordered by a medical provider after a face-to-face evaluation (in person or via telemedicine). It should not be used to screen people who have no symptoms. And the raw data must be reviewed and interpreted by a board-certified sleep medicine physician, not just auto-scored by the device’s software. If a home test comes back normal but your symptoms are strong, your doctor will typically follow up with an in-lab study, since home tests can underestimate the severity of apnea by missing events that occur during brief awakenings the device doesn’t detect.
How Severity Is Measured
The main number that comes out of any sleep study is the Apnea-Hypopnea Index, or AHI. This counts the average number of times per hour that your breathing fully stops (apnea) or partially decreases (hypopnea) during sleep. The American Academy of Sleep Medicine breaks it into three tiers for adults:
- 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
An AHI below 5 is considered normal. Your report will also include your lowest oxygen saturation during the night, how long you spent below certain oxygen thresholds, and how your events distributed across sleep positions and sleep stages. Some people only have apnea while sleeping on their back, for instance, which changes the treatment approach. Children are scored on a stricter scale because even a few events per hour can be clinically significant in a developing brain and body.
Obstructive vs. Central Sleep Apnea
A sleep study doesn’t just count breathing pauses. It also determines what’s causing them, which matters for treatment. In obstructive sleep apnea, the airway physically collapses but your chest and abdomen keep trying to breathe. In central sleep apnea, the brain temporarily stops sending the signal to breathe, so both airflow and breathing effort cease at the same time. The sensors wrapped around your chest and abdomen are specifically there to make this distinction. If both your airflow and your effort drop simultaneously, without signs of obstruction like snoring or a mismatch between chest and abdominal movement, the event is scored as central.
This is one reason an in-lab study matters for complex cases. Home devices don’t always have the sensor resolution to reliably separate obstructive from central events. Central sleep apnea requires a different treatment strategy, and misclassification can lead to the wrong therapy.
What Happens After Diagnosis
Once your results are scored and your AHI falls into the mild, moderate, or severe range, your sleep medicine physician will discuss treatment options tailored to your severity and the type of apnea you have. For moderate to severe obstructive sleep apnea, positive airway pressure therapy (CPAP or similar devices) is the most common first step. Mild cases may be managed with an oral appliance that repositions your jaw, positional therapy if events cluster on your back, or weight loss if that’s a contributing factor.
You may need a follow-up study, either in the lab or at home, to confirm that treatment is working. The goal is to bring your AHI below 5 and resolve symptoms like daytime sleepiness, morning headaches, and fragmented sleep. If your first study was done at home and results were inconclusive, expect your doctor to recommend a full in-lab polysomnography to get the complete picture.