What to Expect in Overnight Sleep Study Testing Called Polysomnograms

Preparing for Your Polysomnogram to Identify Sleep Disorders

What to expect in overnight sleep study testing includes how to prepare, what happens during the study, and when results are interpreted
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So your doctor recommends you undergo overnight sleep study testing to assess snoring or daytime sleepiness for a sleep disorder like sleep apnea, but what should you expect? Polysomnograms are typically done in specialized sleep testing centers. Though you may have some anxiety about the experience, take a few moments, read on and lay those fears to rest. Discover the purpose of sleep testing, how to prepare before the visit, what to expect when you arrive, what happens if you can't sleep, and how soon you will receive the interpretation of the results.

What Is the Purpose of Sleep Testing?

Sleep studies, or polysomnograms, are tests to diagnose sleep disorders, including:

These tests generally involve spending the night sleeping at a sleep laboratory or sleep center. Typically, these studies will be ordered after you have seen a healthcare provider at a clinic visit and have discussed your sleep problems. These tests are the best means to understand how you sleep.

Before Your Sleep Study Visit

Prior to arriving for your sleep study, there are some important preparations that should be made. Most sleep laboratories will have patients arrive in the early evening hours, but check with your center before your appointment. If you work nights, some facilities are able to accommodate studies done during the day. It may be important to avoid caffeine and naps the day of your study, as these may interfere with your ability to sleep. Alcohol intake should not exceed your usual habits.

Restrictions on What to Bring to the Sleep Center

It will be important to check with your sleep center to see if they have special restrictions for you. In general, patients are encouraged to bring:

  • Medications taken at night (or upon awakening)
  • Toiletries
  • Comfortable sleepwear (pajamas or T-shirt and shorts)
  • Favorite pillows or blankets
  • "Comfort items" needed to sleep (such as your childhood teddy bear)
  • Snacks
  • Phone charger

Bring the same items you would usually bring to a stay overnight at a hotel.

Unfortunately, pets and bed partners will not generally be accommodated. If you have a service animal, bring the required documentation. In some cases, a rollaway bed (or cot) can be available for the parent of a child or if someone is unable to stay alone due to a medical condition (dementia, disability, etc.).

If there is something you can’t sleep without, it may not hurt to ask ahead of time.

What to Expect at the Sleep Center

There are hundreds of sleep centers across the country, and each one will vary some in its accommodations. Some are based in hospital wards, others in free-standing buildings and, still others, in empty hotel rooms.

There will be a bed and linens, bathroom facilities, and the equipment necessary to complete the study. There may be bedroom furniture, a television, and a range of other amenities.

Some rooms are sparse and others are extravagant. If you are curious about what the rooms look like, ask to arrange a visit to tour the facilities during the daytime.

Getting Set Up for the Overnight Sleep Study

After arriving and making yourself comfortable, the sleep technician—or sleep tech—will ask you to change into your sleepwear. Everyone will be more comfortable if you wear something to bed, but if you don’t routinely wear pajamas, a loose-fitting T-shirt and shorts will do nicely. The technician will then spend about 45 to 60 minutes setting you up for your sleep study. This time can vary, depending on their efficiency and the complexity of your individual set-up. Some studies for seizures may take as long as 90 minutes to two hours to set up.

The technician will measure the dimensions of your head and mark landmarks on your scalp with a marking pencil. The marks are not permanent and will wash off with soap and water. At designated places, a small cotton-tipped applicator, such as a Q-tip, will be used to clean a small patch of your skin. The cleaning paste is a little abrasive, but it is important to clean off the oils of your skin to optimize the contact for the electrode.

Then wires with gold-cupped electrodes will be put in to place for the EEG. Paste will be applied to each electrode. It serves to keep the wires in place as well as to better conduct the electrical waves of your brain. This paste is often sticky, similar to shortening used in cooking, but will also wash off with hot water with a little persistence. Some of the wires on the face will be taped in place. There are no needles in modern sleep electrodes, and this preparation should not hurt.

In addition to the electrodes on your face and scalp, there are a few other items that shall be applied. The exact set-up may vary from one sleep center to another, but these are standard to most:

  • A flat, plastic snore microphone taped to your neck
  • Sticky pads on your chest to monitor your heart rhythm via an EKG
  • Stretchy cloth belts that go across the chest and stomach to measure breathing
  • Sticky pads or electrodes applied to your shins or forearms to monitor movements (an EMG)

All of these wires will be connected to a small box. This box can be carried around, so don’t worry that you won’t be able to get up after being wired. Trips to the bathroom are accommodated. 

Finally, just before going to bed, a nasal cannula—which is plastic tubing that sits in the nose—will be applied. It will not give you oxygen, but will rather measure airflow. Most laboratories will also use a thermistor, which is a pronged wire that sits in the nostrils and measures temperature differences.

What to Do Before You Sleep

After getting set up, some patients worry about what they will be doing before they sleep. Most technicians will have one or two other patients to set up, so you will have some time when you are left alone. It is important to not fall asleep before starting the study, and most people bring reading materials or other things to work on. It is likely possible to bring your smartphone, computer, a portable DVD player, or even something to listen to. Many people find the evening very relaxing—there are no dishes to be done and no one else around to bother you!

Some centers will have their patients watch an educational video about sleep disorders. If you are likely to need continuous positive airway pressure (CPAP) during the night, you may be fitted with a mask and practice with this before going to bed.

When the Night Begins

When you have reached your bedtime, or you feel drowsy enough to fall asleep, it will be important to let your technician know. They will help you into bed and connect the wire box to a computer that will allow the tech to monitor you from another room. There will likely be a small infrared camera and two-way speaker in the bedroom. If you need to get up during the night, this is how you will call for assistance.

Just prior to going to sleep, the technician will need to test the equipment. As part of this testing, you will open and close your eyes, move them around, snore, take breaths in and out, and even move your arms and legs. If something goes wrong with a wire, or if one comes loose during the night, your technician will come in to fix it.

Will I Sleep in a Sleep Test—and What If I Can't?

The biggest concern most people have is whether they will be able to sleep. Surprisingly, most individuals are able to sleep, even with all the wires, the strange environment, and any number of things that could be disruptive. It is exceptionally rare to have someone not be able to sleep at all.

If you are concerned that you may not be able to fall asleep, some healthcare providers prescribe a sleeping medication or sleeping pill to be used the night of the study. There are some that will not change the results of your sleep study, including the most commonly prescribed one called zolpidem (Ambien). Make certain that all medications are approved by your doctor before using them the night of the study.

In the worst-case scenario, the testing can be repeated as necessary to ensure adequate sleep observation is obtained and the results are valid. Don't feel stressed though: the vast majority of people are successful during their first attempt at a study.

The Morning After the Sleep Study

Most people get up at a regular time, and if you let your sleep technician know this before going to bed, they will be happy to wake you (there may be no clocks in the bedroom). The wires and other measurement devices will be removed with surprising speed, perhaps in as little as 5 to 10 minutes. There may be a questionnaire about your night's sleep to complete.

Some centers have showers, and you may be able to get ready for your day before leaving. (Remember that the sleep technicians have been awake all night, and they are eager to get home to sleep, too.)

You will likely not be given any information about your study until a sleep doctor has had a chance to review the results, which could be a few weeks. Most patients will meet with the doctor in clinic to discuss the interpretation of the study's findings and to review possible treatments if a sleep disorder is identified.

A Word From Verywell

If you have further questions or concerns, don't hesitate to contact either the testing center or the doctor who ordered the testing on your behalf. In some cases, home sleep apnea testing may be an acceptable alternative.


Berry RB et al. "The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications, Version 2.2." Darien, Illinois: American Academy of Sleep Medicine, 2015.