Sleep Study
Reviewed
Also called: Polysomnography, Sleep apnea study, Home sleep study
A sleep study measures body functions while you sleep to diagnose sleep disorders. It is typically done overnight at a sleep center or at home. Electrodes record breathing, heart rate, oxygen levels, brain waves, and movements. For a home study, you attach the sensors yourself. Results include indices like AHI and oxygen desaturation. Your provider will interpret the results and recommend treatment if needed.
Specimen: N/A
Urgent safety information
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Why this test may be ordered
- You have symptoms of a sleep disorder, such as loud snoring, gasping for breath during sleep, trouble falling or staying asleep, or excessive daytime sleepiness that may increase the risk of accidents.
- You have a known condition that can be affected by sleep disorders, such as depression, diabetes, or heart disease.
- Your provider wants to evaluate the severity of a suspected sleep disorder to guide treatment.
Preparation and collection
Avoid alcohol and caffeine in the afternoon and evening before the test. Do not nap during the day. Do not use lotions, hair gels, or makeup. Avoid nail polish or artificial nails. If you take sleep medicines, ask your provider whether to take them before the test.
Overnight monitoring at a sleep center or at home with equipment provided by a healthcare provider. Electrodes are attached to the scalp, eyelids, chin, chest, and legs. A pulse oximeter is placed on a finger or ear. In-lab studies include video and audio monitoring by a polysomnography technologist.
You may have mild skin irritation from the electrodes. The source states there are no other known risks. In-lab studies involve video monitoring for safety.
Understanding results
A sleep study (polysomnography) measures breathing, heart rate, oxygen levels, brain waves, and movements during sleep. Results are used to diagnose sleep disorders such as sleep apnea, insomnia, restless leg syndrome, and narcolepsy. Your healthcare provider will interpret all measurements together.
- Apnea-Hypopnea Index (AHI): Lower likelihood: 5 or fewer apnea-hypopnea episodes per night. Higher likelihood: more than 5 episodes per night, which probably indicates sleep apnea. Limitation: The AHI count may vary from night to night; a single night may not fully represent your typical sleep. Next step: If more than 5 episodes are recorded, your provider will discuss treatment options such as lifestyle changes, CPAP, or dental devices.
- Oxygen Desaturation Index (ODI): Normal: oxygen levels remain above 90% during sleep. Abnormal: oxygen level drops below 90%, which is considered abnormal. Limitation: Oxygen levels can be affected by movement or sensor placement; repeated drops below 90% are needed for concern. Next step: If oxygen drops below 90% during sleep, your provider may recommend further evaluation or treatment for sleep apnea.
- Home sleep studies use fewer sensors and are only used to diagnose obstructive sleep apnea; they are not recommended if you have other sleep disorders or health conditions that could affect breathing.
- You may not sleep as well during the study, but a full night's sleep is not necessary for results.
- In-lab studies involve a low-light video camera to record movements, which may raise privacy concerns for some individuals.
What to do next
If your results suggest a sleep disorder, your provider will discuss the findings and recommend a treatment plan. For sleep apnea, this may include lifestyle changes, a CPAP machine, dental devices, or surgery depending on your specific condition.
- What were my AHI (Apnea-Hypopnea Index) and sleep efficiency?
- How does my oxygen desaturation index (ODI) compare to normal?
- What do my results mean for my overall health and safety?
- Do I need further testing or a referral to a sleep specialist?