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What to Expect at a Sleep Study

A sleep study can feel unfamiliar, but knowing what to expect makes it much easier. Here is a practical walkthrough of both in-lab and home sleep studies.

In-Lab Study

Overnight polysomnography (PSG)

An in-lab sleep study is performed at a sleep center, usually overnight. It is the most comprehensive type of sleep study and is considered the gold standard for diagnosing sleep disorders.[1]

A real patient fully set up for an overnight in-lab sleep study, with EEG electrodes glued to the scalp, sensors on the face, and belts around the chest and abdomen
How you’ll be set up for an in-lab sleep study. A technologist attaches each sensor while you relax — nothing pierces the skin, none of it hurts, and everything comes off easily in the morning. Photo via Wikimedia Commons (free license — see file page for author credit).
Video · Bozeman Health Sleep Center

Watch: what happens during an in-lab sleep study

A real sleep center walkthrough — the room, the hookup, and the overnight monitoring.

Good to know

  • Most people are surprised how normal the room feels — more hotel than hospital.
  • You do not need a perfect night of sleep. A few recorded hours is usually enough.
  • The paste washes out with warm water and shampoo the next morning.
A person set up for polysomnography lying comfortably on their side in bed
You can still sleep in your usual position. The wires have plenty of slack — side sleeping, turning over, and getting up for the bathroom are all fine. Photo via Wikimedia Commons (free license — see file page for author credit).
A patient wired up for a sleep study, showing the sensor wires gathered together
The wires all gather into one connector. It looks like a lot, but you can still turn over and get up. Photo via Wikimedia Commons (free license — see file page for author credit).

Before the study

  • Avoid caffeine after noon on the day of your study.
  • Avoid alcohol on the day of your study — it affects sleep architecture and can mask or worsen sleep-disordered breathing.
  • Avoid naps the day of the study so you are sleepy at bedtime.
  • Shower and wash your hair. Avoid hair products, lotions, and makeup — they interfere with sensor adhesion.
  • Take your regular medications unless your sleep provider instructs otherwise.
  • Pack comfortable pajamas, toiletries, a change of clothes for the morning, any medications you take at bedtime, and your CPAP if you already use one.
  • Arrive on time — typically between 8:00 and 9:30 PM. The setup process takes about 30–45 minutes.
  • Bring your insurance card and photo ID.

During the study

  • You'll have your own room — typically a private, hotel-like bedroom. You can bring your own pillow if you prefer.
  • A technologist will attach sensors to your scalp (EEG), face (EOG, chin EMG), chest and abdomen (breathing effort), finger (pulse oximetry), and legs (leg movement sensors). A nasal cannula measures airflow. Sensors are attached with paste or adhesive — they don't hurt.
  • Wires connect to a box near the bed. You can move, turn over, and get up to use the restroom (the technologist will assist with disconnecting if needed).
  • A low-light camera and microphone allow the technologist to monitor you from another room. You can communicate via intercom.
  • You don't need to sleep perfectly. Most people worry they won't sleep — but even a few hours of recorded sleep is usually enough for diagnosis. The technologist will tell you when to try to sleep and when the study is done (usually by 6:00 AM).
  • If a split-night study is planned, the technologist may wake you partway through to fit a CPAP mask and titrate the pressure during the second half of the night.
Your Night, Step by Step

A typical in-lab study timeline

  1. 8:00 – 9:30 PMArrive and settle inYou'll check in, see your private room, change into your own pajamas, and complete a short questionnaire.
  2. ≈ 45 minutesSensor hookupThe technologist attaches each sensor while you sit comfortably — scalp, face, chest, finger, and legs. Nothing hurts.
  3. 10:00 – 11:00 PMLights outYou sleep in a normal bed. The technologist monitors from another room and can hear you through an intercom if you need anything.
  4. OvernightRecordingBrain waves, breathing, oxygen, heart rhythm, and movement are recorded continuously. In a split-night study, CPAP may be fitted partway through.
  5. ≈ 6:00 AMWake-up and disconnectSensors come off in minutes. You can shower, dress, and head straight to work if you like.
  6. 1 – 2 weeksResultsA sleep physician scores the study and your provider reviews the results and next steps with you.
What's Measured

What sensors monitor overnight

  • Brain waves (EEG): Determines sleep stages (N1, N2, N3 deep sleep, REM) and wakefulness.
  • Eye movements (EOG): Identifies REM sleep.
  • Muscle activity (EMG): Chin EMG for REM sleep confirmation; leg EMG for periodic limb movements.
  • Airflow (nasal cannula + thermistor): Detects apneas (complete pauses) and hypopneas (partial reductions) in breathing.
  • Breathing effort (chest and abdominal belts): Distinguishes obstructive events (effort present) from central events (no effort).
  • Oxygen saturation (pulse oximetry): Monitors blood oxygen levels throughout the night.
  • Heart rhythm (ECG): Single-lead electrocardiogram to detect arrhythmias.
  • Body position: Records whether you are on your back, side, or stomach — important because OSA is often worse when supine.
  • Snoring microphone: Records snoring intensity and timing.
Home Sleep Test

Home sleep apnea testing (HSAT)

A home sleep apnea test is a simpler, portable alternative that you use in your own bed. It is appropriate for patients with a high likelihood of moderate-to-severe obstructive sleep apnea without significant other medical conditions.[1]

How it works

  • You pick up the device from your sleep clinic or it is mailed to you.
  • The device typically includes a nasal cannula (airflow), a finger probe (oxygen), a chest belt (breathing effort), and sometimes a body position sensor.
  • You set it up yourself at bedtime following the instructions — it takes about 5–10 minutes.
  • Sleep in your own bed as normally as possible.
  • Return the device the next day (or after 1–3 nights depending on the protocol).
  • A sleep provider reviews the data and contacts you with results.

Important limitations

  • Does not measure sleep stages: HSAT cannot tell when you are asleep vs. awake, so it may underestimate the severity of sleep apnea.
  • A negative HSAT does not rule out OSA: If the home test is normal or inconclusive but symptoms persist, an in-lab polysomnography is recommended.[1]
  • Not appropriate for everyone: Patients with significant heart failure, severe lung disease, neuromuscular disease, suspected central sleep apnea, or other complex sleep disorders should have an in-lab study.[1]
  • Data quality depends on setup: Loose sensors or poor signal can produce unreliable results. Follow the setup instructions carefully.
Video · ResMed

Setting up the ApneaLink Air home test

Step-by-step setup for one of the most commonly dispensed home sleep test devices.

Video · Philips

Setting up the Alice NightOne home test

If your clinic gave you a different device, the steps are similar — belt, cannula, finger probe.

After the Study

Results and next steps

Understanding your results

  • Apnea-Hypopnea Index (AHI): The number of breathing pauses (apneas) and partial reductions (hypopneas) per hour of sleep. This is the primary measure of OSA severity.[1]
  • Normal: AHI < 5
  • Mild OSA: AHI 5–14
  • Moderate OSA: AHI 15–29
  • Severe OSA: AHI ≥ 30
  • Oxygen desaturation: Time spent with oxygen below 90% or 88%. Important for assessing severity and cardiovascular risk.
  • Sleep architecture: In-lab studies also report time in each sleep stage, sleep efficiency, and leg movement data.

What comes next

  • Your sleep provider will review results and discuss diagnosis and treatment options with you.
  • If OSA is diagnosed, treatment may include CPAP/APAP, oral appliance therapy, positional therapy, or lifestyle modifications depending on severity and preferences.
  • If the study was inconclusive, a repeat study or alternative testing may be recommended.
  • Results are typically available within 1–2 weeks.
  • Bring questions to your follow-up appointment — understanding your results helps you engage with treatment.
Common Worries

Questions patients ask most

Will the sensors hurt?

No. Everything attaches with paste, gel, stickers, or soft elastic belts. Nothing pierces the skin, and removal in the morning takes only a few minutes.

What if I can't fall asleep?

This is the most common worry — and it almost never ruins the study. Even a few hours of recorded sleep is usually enough for a diagnosis. Avoid naps and caffeine that day so you're sleepy at bedtime.

Can I sleep on my side or turn over?

Yes. The wires gather into a single connector near the bed with enough slack to turn freely. Sleeping in different positions is actually useful data.

What if I need the bathroom overnight?

Just say so out loud — the technologist hears you on the intercom and will unclip the connector so you can walk to the bathroom normally.

Does the paste come out of my hair?

Yes — warm water and regular shampoo remove it. Most sleep centers have showers so you can rinse off before leaving.

Can someone come with me?

Policies vary by sleep center. Caregivers can usually stay for patients who need assistance — call your center ahead of time to confirm.

Trusted resources

Related topics

References

  1. Kapur VK, Auckley DH, Chowdhuri S, et al. Clinical practice guideline for diagnostic testing for adult obstructive sleep apnea: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2017;13(3):479-504. doi:10.5664/jcsm.6506