What Is Polysomnography? A Complete Guide to In-Lab Sleep Studies

Quick answer: Polysomnography is the overnight in-lab sleep study. About two dozen sensors record brain waves, breathing, oxygen levels, and heart rhythm while you sleep at a sleep lab. It's the most thorough sleep test in medicine and the right choice for complex cases, but for most adults with suspected sleep apnea, a home sleep test answers the same diagnostic question.

If your doctor mentioned "polysomnography" and you went looking for what it actually means, here's the short version. You spend a night at a sleep lab. A technologist sticks sensors to your scalp, your face, your chest, and your legs. About two dozen physiologic channels record simultaneously while you sleep. In the morning, a board-certified sleep physician reads the recording and writes a report.

Polysomnography is the gold standard for diagnosing complex sleep disorders. It's also typically $1,500 to $3,000 in California, requires a full night away from home, and is more than most patients with simple obstructive sleep apnea actually need. The home sleep test answers the same yes-or-no diagnostic question for around $200, which is why the American Academy of Sleep Medicine recommends home testing as the first study for adults with moderate-to-high pretest probability of OSA (AASM Clinical Practice Guideline, 2017, reaffirmed 2023).

What does polysomnography measure?

A full PSG attaches roughly two dozen sensors and records every channel continuously through the night. The point of recording everything at once is that sleep disorders rarely show up on a single channel, diagnosis often comes from how the channels relate to each other (an oxygen drop with a corresponding brain-wave arousal, for example).

• Electroencephalogram (EEG) — brain waves, used to identify sleep stages (N1, N2, N3, REM)
• Electrooculogram (EOG) — eye movements, the signal that confirms REM sleep
• Electromyogram (EMG) — chin and leg muscle activity
• Electrocardiogram (ECG) — heart rhythm
• Nasal and oral airflow sensors
• Chest and abdominal effort belts
• Pulse oximetry — blood oxygen saturation
• Audio and video recording for snoring and body position

What happens the night of a sleep study?

You arrive at the lab around 8 or 9pm. A technologist spends 45 to 60 minutes attaching sensors with a paste that washes out the next morning (it looks worse than it is). Once everything's connected, you settle into a private bedroom, most labs are designed to look hotel-ish rather than clinical, and the technologist monitors from a control room down the hall.

Almost everyone sleeps worse on the first night than they do at home. This is well-documented enough to have a name: the first-night effect. Don't worry about it. The recording captures plenty of data even from interrupted sleep, and the diagnostic conclusions hold up. You'll be woken between 5 and 6am, the sensors come off, and you drive home. A technologist scores the recording over the next day or two; a sleep physician interprets it; the report goes to your ordering doctor.

When does my doctor order polysomnography?

There are real clinical reasons in-lab testing is the right call. The AASM guidelines reserve PSG for cases where home testing can't reliably answer the question:

• Suspected central sleep apnea (the brain fails to signal breathing muscles, separate from obstructive apnea)
• Suspected mixed/complex apnea
• Significant heart failure or severe COPD that complicates oxygen interpretation
• Suspected narcolepsy, REM behavior disorder, or periodic limb movement disorder
• Neuromuscular disease
• Children under 18
• A non-diagnostic home sleep test in a patient with persistent high-suspicion symptoms

When can a home sleep test do the same job?

If you're an adult with the textbook OSA picture, loud habitual snoring, witnessed pauses in breathing, daytime sleepiness, plus one or more of: BMI over 30, hypertension, or a thick neck, AASM guidelines explicitly support home testing as the right first study.

Home tests record airflow, oxygen, heart rate, and breathing effort. They don't record brain waves, so they can't stage sleep. For diagnosing obstructive sleep apnea, that's fine, sleep staging isn't required. The apnea-hypopnea index (AHI) from a home test is treated as diagnostic when the pretest probability is moderate or higher.

How much does polysomnography cost?

• Polysomnography in California: typically $1,500–$3,000 before insurance, with a wide spread by facility (hospital-based labs charge more than freestanding accredited labs).
• Home sleep test: $150–$400 before insurance, taken in your own bed, no missed work day.
• Both are typically covered by Medicare and major commercial plans when ordered for an appropriate indication. CPT 95810 is the in-lab attended PSG code; 95800 covers most home tests.

How do I decide which test fits?

You don't, actually, your doctor does. All sleep testing requires a physician order, and the test gets matched to your clinical picture. What you can do is advocate for the home test if your situation is uncomplicated; most physicians will agree when there are no central apnea symptoms, no comorbid heart or lung disease, and no other sleep disorders to rule out.

Advanced Sleep Medicine Services has performed home sleep testing throughout California since 1994. We're accredited by the Accreditation Commission for Health Care (ACHC), and our board-certified sleep physicians read every study. If your doctor has ordered a sleep test, we ship an FDA-approved device to your home and have results back within a few days. We accept 100+ insurance plans, call (877) 775-3377 to verify yours.