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Counting Sheep: An Overview of Sleep Studies

Written by Alexandra Fuhs

Edited by Shania Sheth and Jocelyn Wang


Hi everyone! This article is the first article in our Sleep Medicine series, where we dive deep into how sleep affects the human body and health. Read on to learn about sleep disorders, and how they can be diagnosed.


Everyone knows about the recommended eight hours of sleep per night, but some people find that difficult to achieve for reasons other than late-night Netflix marathons or too much caffeine. Sleep studies help diagnose sleep disorders such as sleep apnea, insomnia, and narcolepsy. Because the issues arise when a patient is asleep, these disorders are difficult to diagnose with a regular office visit. The studies are non-invasive tests that take place in a center specially designed for these overnight stays (usually in a hospital or a specialized sleep center). Patients’ sleep stages, cycles, and functions such as heart rate are monitored through sensors when they’re asleep by a technician, and later evaluated by a doctor. While there are multiple kinds of sleep studies, there are three main ones that are used to diagnose the most common sleep disorders.

Multiple Sleep Latency Test:

This test is used to diagnose the severity of daytime tiredness and is conducted the day after a nighttime sleep test. During the test, the patient is given four to five opportunities to take a short nap with two-hour breaks in between the naps. While they are allowed to leave the laboratory during the breaks, they are instructed to stay awake and may not eat or drink anything containing caffeine.

The results of the MSLT determine how long it takes a patient to fall asleep and provide information on sleep latency (how long it took them to fall asleep). Using this test, the criteria to be diagnosed with narcolepsy is an average sleep latency of less than eight minutes across all the naps and the occurrence of at least two sleep-onset REM periods (SOREMP) — REM sleep experienced shortly after a person falls asleep. The insomnia diagnosis criteria is also an average sleep latency of less than eight minutes, but less than two SOREMPs, meaning the patient did not experience REM sleep.


A polysomnography can be used to diagnose various sleep disorders such as sleep apnea, seizure disorders, and restless legs syndrome, as well as narcolepsy and insomnia. During a polysomnography, a technician uses electrodes placed on the eyelids, chin, scalp, and chest to monitor the patient’s brain waves, heart rate and rhythm, and blood pressure, as well as observe body movements and snoring. While it may be difficult for patients to fall asleep, a polysomnography does not necessarily require a full night of sleep, so the data would not be affected.

CPAP Titration Study:

Sleep disorders such as sleep apnea cause people to experience momentary lapses in breathing, which can lead to fatigue, daytime tiredness, and trouble sleeping. One treatment is to use a CPAP machine, which blows air into a person’s nose or mouth to help keep their airway open. A CPAP titration study is used to determine the ideal rate of airflow needed to treat a patient with sleep apnea.

A polysomnography is conducted with a CPAP machine. As the patient sleeps, the rate of airflow through the CPAP machine is increased in small increments. When the patient no longer has lapses in breathing, that rate of airflow is selected for their CPAP machine. There are two types of this study, a full-night and split-night study. In a full-night study, the CPAP machine is calibrated for the entire time, whereas in a split-night study, the first portion of the night is used to diagnose the sleep disorder that the patient is suffering from, and the second portion is used to calibrate the machine.


Thanks for reading the first article in our Sleep Medicine series! We hope you learned about different methods that sleep disorders can be diagnosed and treated.

If you liked reading this article, check out our article on South Asian culture, linked here.

Thank you for reading, and until next time,

Alexandra and the Writing Committee :)


  1. American Thoracic Society. “Multiple Sleep Latency Test”. Patient Education Information Series.

  1. Summer, Jay. “Multiple Sleep Latency Test MSLT”. Sleep Foundation, 27 April 2022.

  1. Giorgi, Anna. “Polysomnography”. Healthline, 17 March 2020.

  1. Summer, Jay. “CPAP Titration Sleep Study”. Sleep Foundation, 23 September 2022.

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