Polysomnography, commonly known as a sleep test, is a diagnostic tool used to identify sleep disorders. It comprehensively records your brain waves, blood oxygen levels, heart rate, breathing patterns, and also monitors eye and leg movements during sleep. This provides valuable information for diagnosing and managing various sleep-related conditions.
Why is a Sleep Test Performed?
A sleep study is essential for monitoring your sleep stages and cycles. It helps determine if your sleep patterns are disrupted, when these disruptions occur, and the underlying causes. The process involves identifying the different stages of sleep, including non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep.
During NREM sleep, brain waves slow down, a change recorded using an electroencephalogram (EEG). After an hour or two in NREM, brain activity increases, marking the start of REM sleep, characterized by rapid eye movements and most dreaming. These cycles between NREM and REM typically occur every 90 minutes throughout the night. Sleep disorders can significantly interfere with these cycles, and a sleep test helps pinpoint the specific issues.
Your healthcare provider may recommend a sleep test if they suspect you have any of the following conditions:
- Sleep apnea or other sleep-related breathing disorders: This condition involves repeated pauses and restarts in breathing during sleep.
- Periodic limb movement disorder (PLMD): People with PLMD experience repetitive flexing and extending of their legs during sleep, sometimes linked to restless legs syndrome (RLS).
- Narcolepsy: Individuals with narcolepsy suffer from excessive daytime sleepiness and may experience sudden sleep attacks.
- REM sleep behavior disorder (RBD): RBD involves acting out dreams during sleep, potentially leading to injury.
- Unusual behaviors during sleep: This can include sleepwalking, moving around excessively, or engaging in rhythmic movements.
- Chronic insomnia: Insomnia is characterized by difficulty falling asleep, staying asleep, or both.
Where are Sleep Tests Conducted?
Sleep studies can be performed in a dedicated sleep disorders unit within a hospital or at a specialized sleep center. Typically, the test is conducted at night to align with normal sleep patterns. However, for shift workers who regularly sleep during the day, the test can be scheduled accordingly.
In some cases, a sleep study can be done at home using a home sleep apnea test (HSAT) device. These tests primarily focus on diagnosing obstructive sleep apnea (OSA) and record breathing rate, airflow, oxygen levels, and heart rate. Some HSATs also gather data on blood vessel activity. Different types of HSAT devices are available, each employing a unique combination of sensors.
What to Expect During a Sleep Test
Whether conducted in a sleep center or at home, understanding the process can alleviate anxiety.
Polysomnography in a Sleep Center
If you are undergoing a sleep study at a sleep center, you’ll arrive in the evening and stay overnight. To make the experience more comfortable, you can bring items you normally use for your bedtime routine, such as your pillow or favorite book. You’re also welcome to wear your own nightclothes.
The room where the polysomnography is performed resembles a typical hotel room, designed to be dark and quiet. You’ll have your own private bathroom.
The room is equipped with a low-light video camera that allows technologists to monitor your movements without disturbing you. An audio system enables communication between you and the technologists, who are stationed in a monitoring area outside the room.
Before you go to sleep, a technologist will attach sensors to your scalp, temples, chest, and legs using a mild adhesive. A small clip will also be placed on your finger or ear to monitor your blood oxygen level. These sensors are connected to a computer via wires that are long enough to allow you to move comfortably in bed.
Throughout the night, the technologist will monitor various parameters, including:
- Brain waves
- Eye movements
- Heart rate
- Breathing pattern
- Blood oxygen level
- Body position
- Chest and abdominal movement
- Limb movement
- Snoring and other noises
The technologists remain vigilant throughout the night and can communicate with you if you need assistance. They can also enter the room to adjust the wires if you need to get up.
During the study, the technologist may introduce a positive airway pressure (PAP) machine, like a Continuous Positive Airway Pressure (CPAP) or Bilevel Positive Airway Pressure (BPAP) device, particularly if sleep apnea is suspected. These devices deliver a stream of air through a mask to help keep your airway open while you sleep. You may have the opportunity to try on a PAP device before the study begins to familiarize yourself with it. Oxygen may also be administered during the study to aid your breathing if needed.
Although sleeping at a sleep center might not be as comfortable as sleeping at home, this generally doesn’t affect the accuracy of the results. A full night’s sleep is not required for obtaining reliable polysomnography data.
Home Sleep Apnea Test
With a home sleep apnea test, the equipment will be delivered to your home or you’ll pick it up from your healthcare provider’s office. Detailed instructions on how to use the equipment will be provided. Be sure to ask questions if anything is unclear.
You’ll follow your regular bedtime schedule, attaching the sensors to your body and turning on the machine according to the instructions. Your healthcare provider may also ask you to keep a sleep log.
Preparing for a Sleep Test
To ensure the accuracy of your sleep study, avoid alcohol and caffeine in the afternoon and evening before the test, as these substances can alter your sleep patterns and potentially worsen symptoms of certain sleep disorders. Also, avoid napping before the test.
You may be asked to shower or bathe before the study, but refrain from using lotions, gels, colognes, or makeup, as these products can interfere with the sensors.
Risks Associated with Polysomnography
Polysomnography is a non-invasive and painless test. The most common side effect is mild skin irritation caused by the adhesive used to attach the sensors.
Understanding the Results
The measurements recorded during a sleep study provide a wealth of information about your sleep patterns, including:
- Brain waves and eye movements: These help assess your sleep stages and identify any disruptions, which may indicate conditions like narcolepsy or REM sleep behavior disorder.
- Heart and breathing rate changes, and blood oxygen levels: Atypical changes can suggest sleep apnea.
- PAP or oxygen usage: Data from these interventions can help determine the best settings for home use, if prescribed.
- Frequent leg movements: These may indicate periodic limb movement disorder.
- Movements or behaviors during sleep: These can be signs of REM sleep behavior disorder or other sleep disorders.
Following the sleep study, a polysomnography technologist will analyze the data to chart your sleep stages and cycles. This information is then reviewed by your healthcare provider, who will discuss the results with you during a follow-up appointment. Based on the findings, they will recommend appropriate treatment or further evaluation, if necessary.
If you underwent a home sleep apnea test, your healthcare provider will review the data collected. It may take a few days or weeks to receive your results. If the results are inconclusive, your healthcare provider may recommend an in-lab sleep study for more comprehensive evaluation.
