Can’t Sleep Through the Night? Here’s What a Sleep Study Can Reveal
If you keep waking up during the night, a sleep study can show why, and that is one of the main benefits of a sleep study. A sleep study, also called polysomnography, is a painless test that measures how well you sleep and how your body responds to sleep problems, and doctors use it to help diagnose sleep disorders (NHLBI). This guide explains what a sleep study records, which disorders it can help identify, and how a home test differs from an in-lab study. For the night itself, see our page on sleep studies at Vector.
This article was reviewed by Dmitriy Kolesnik, MD, a neurologist board certified in Sleep Medicine and Medical Director of Vector Sleep Diagnostic Center in Rego Park, Queens.
Vector has served patients since 2005 and runs 900 to 1000 overnight sleep studies a year. Our medical director, Dr. Dmitriy Kolesnik, is board certified in neurology and sleep medicine.
What a Sleep Study Actually Measures
The most common type of sleep study records brain waves and monitors your heart rate, breathing and the oxygen level in your blood during a full night of sleep, according to NHLBI. At a sleep center the test usually lasts overnight. Removable sensors are placed on your scalp, face, eyelids, chest, limbs and a finger, and they record:
- Brain waves. Scalp sensors record brain activity (EEG) through the night.
- Heart rate. Chest sensors monitor how your heart behaves while you sleep.
- Breathing effort and rate. Sensors track how hard you work to breathe and how often.
- Oxygen levels. A finger sensor reads the oxygen level in your blood.
- Muscle movements. Sensors on the limbs record movement before, during and after sleep.
Sleep Disorders a Sleep Study Can Help Diagnose
NHLBI says sleep tests can help diagnose sleep related breathing disorders such as sleep apnea, sleep related seizure disorders, sleep related movement disorders, and sleep disorders that cause extreme daytime tiredness such as narcolepsy. Doctors also use them to help diagnose or rule out restless legs syndrome. The sections below cover the ones people ask us about most.
Sleep Apnea
The AASM says your medical provider can diagnose obstructive sleep apnea using an in-lab sleep study or a home sleep apnea test. The AASM guideline cites the ICSD-3 definition of obstructive sleep apnea as a respiratory disturbance index of 5 or more events per hour together with typical symptoms such as unrefreshing sleep, daytime sleepiness, loud snoring, awakening with a gasping or choking sensation or witnessed apneas, or 15 or more events per hour even without symptoms. Our sleep apnea care page explains what comes after a diagnosis.
Periodic Limb Movement Disorder and Restless Legs Syndrome
Because the sensors record limb and muscle movement, a sleep study can show movement disorders that you may not notice while asleep. The AASM names periodic limb movement disorder as one of the disorders an overnight study can reveal. NHLBI adds that doctors may use sleep tests to help diagnose or rule out restless legs syndrome. Read more in our guide to restless legs syndrome.
Narcolepsy
The AASM narcolepsy page says doctors combine tests to decide whether you have narcolepsy. An overnight sleep study is one of them, and it can show whether another problem, such as sleep apnea, is causing your excessive daytime sleepiness. The Multiple Sleep Latency Test, also called a nap study, is a second test. It measures how quickly you fall asleep during several naps at set times through the day.
Parasomnias
The AASM describes REM sleep behavior disorder as a parasomnia in which you act out vivid dreams as you sleep. Its patient page says the best sleep study also records your sleep on video, which shows whether you get out of bed or do anything unusual during the night. Our team in Rego Park, Queens can help you decide whether this kind of study fits your symptoms.
In-Lab Sleep Study Versus a Home Sleep Apnea Test
Your doctor decides which one you need (NHLBI). The AASM patient page describes both options.
| Feature | In-lab sleep study | Home sleep apnea test |
|---|---|---|
| Where | Overnight at a sleep center, in a bed that may resemble a hotel room | In your own home |
| What it records | Brain waves, heartbeat, breathing and movement | A small monitor collects breathing data |
| Equipment | Sensors placed on your body for you | Less complicated equipment that you hook up yourself after being shown how |
| Best fit | More complex cases | Patients with many risk factors for sleep apnea and no other medical disorders |
The AASM guideline explains a limit of home testing. Because brain wave channels are usually not monitored at home, the result divides events by recording time rather than sleep time, and devices with conventional sensors cannot detect hypopneas tied only to arousals from sleep. These factors can lead to underestimating the true apnea-hypopnea index. If a single home test is negative, inconclusive or technically inadequate, the guideline strongly recommends an in-lab polysomnogram. For a fuller comparison, see at-home and in-lab sleep studies and our look at how accurate sleep studies are.
The AASM also warns that apps and sleep tracking devices may claim to detect sleep apnea, but their results can be unreliable, so discuss them with your medical provider.
Benefits of a Sleep Study: Why Getting Diagnosed Matters
NHLBI says untreated sleep disorders can raise your risk of heart failure, high blood pressure, stroke, diabetes and depression. Sleep disorders have also been linked to an increased risk of injury and car accidents. The benefits of a sleep study come down to objective data in place of guesswork: about what happens in your brain and body during sleep, and your doctor uses it to build a treatment plan.
Getting Ready for a Sleep Study
- Tell your doctor about snoring, gasping, daytime fatigue and anything a bed partner has noticed. The AASM suggests asking a partner, roommate or relative whether they have heard you snore loudly or make choking noises in your sleep.
- Ask whether your symptoms and medical history call for a home test or an in-lab study.
- Read our night before sleep study checklist so you know what to bring and what to avoid.
- After the study, schedule the follow-up visit to review your results. Our guide to what happens after your sleep study walks through that visit.
Want to see the benefits of a sleep study for your own symptoms? Questions about which test fits you? Email vectorsleep@gmail.com or call (718) 830-2800. Our team at Vector Sleep Diagnostic Center in Rego Park, Queens reviews your symptoms and helps you choose the right study.
Frequently Asked Questions About Sleep Studies
What does a sleep study measure?
NHLBI says the most common type of sleep study records brain waves and monitors your heart rate, breathing and the oxygen level in your blood during a full night of sleep. At a sleep center, removable sensors on the scalp, face, eyelids, chest, limbs and a finger also record breathing effort and rate and muscle movements.
Is a sleep study uncomfortable?
NHLBI describes sleep studies as painless tests. It notes a small risk of skin irritation from the sensors, which goes away after they are removed.
Which sleep disorders can a sleep study help diagnose?
According to NHLBI, sleep tests can help diagnose sleep related breathing disorders such as sleep apnea, sleep related seizure disorders, sleep related movement disorders, and disorders that cause extreme daytime tiredness such as narcolepsy. Doctors also use them to help diagnose or rule out restless legs syndrome.
Do I need an overnight study at a sleep center or can I test at home?
Your doctor decides. NHLBI says your doctor will determine whether you need your sleep test at a sleep center or can do it at home with a portable device. The AASM says a home sleep apnea test suits some patients with many risk factors for sleep apnea and no other medical disorders, and that an in-lab study is usually recommended for more complex cases.
What if my home sleep test is negative but I still feel unrested?
The AASM guideline strongly recommends polysomnography, the in-lab study, when a single home sleep apnea test is negative, inconclusive or technically inadequate. It also notes that home testing can underestimate the true apnea-hypopnea index.
What happens after the sleep study?
The AASM says that after your sleep study or home sleep apnea test you schedule a follow-up appointment to discuss the results, and that if you are diagnosed with sleep apnea your medical provider will talk with you about treatment options. NHLBI says your doctor reviews your results and develops a treatment plan for any diagnosed sleep disorder.
Sources
- NHLBI, Sleep Studies, what a sleep study records, which disorders it helps diagnose, risks of untreated disorders
- American Academy of Sleep Medicine, Sleep Education: Obstructive Sleep Apnea, in-lab versus home testing, apps
- AASM Sleep Education: Narcolepsy, overnight study and the Multiple Sleep Latency Test
- AASM Sleep Education: REM Sleep Behavior Disorder, sleep study with video
- Clinical practice guideline for diagnostic testing for adult obstructive sleep apnea (AASM, Journal of Clinical Sleep Medicine, 2017), definition, home test limits, negative results
