An in-center sleep study, also known as polysomnography, is a diagnostic test used to assess the quality and patterns of a person's sleep. It helps doctors evaluate sleep disorders such as obstructive sleep apnea (OSA), periodic limb movements of sleep (PLMS) associated with restless leg syndrome (RLS), narcolepsy, parasomnias, and other sleep-related conditions. Sleep studies are typically recommended when a patient experiences symptoms like excessive daytime sleepiness, loud snoring, choking during sleep, or difficulty falling and staying asleep.

If you’ve been advised to undergo a sleep study, it’s natural to feel a little anxious or uncertain about what to expect. While the process can seem intimidating at first, understanding the purpose, procedure, and how to prepare can help alleviate some of that stress. This article will walk you through what a sleep study entails, including the different types of studies, the preparation required, the procedure itself, and what happens afterward.

1. Why a Sleep Study Is Recommended

Sleep studies are recommended for a variety of reasons, typically when a sleep disorder is suspected but the symptoms cannot be fully understood through a simple medical history or a physical exam. Common conditions diagnosed through sleep studies include:

Obstructive Sleep Apnea (OSA): Characterized by brief interruptions in breathing during sleep.
Narcolepsy: A condition marked by sudden, uncontrollable sleep episodes during the day and fragmented sleep at night.
Restless Leg Syndrome (RLS): An overwhelming urge to move the legs, often accompanied by discomfort and associated with periodic limb movements of sleep (PLMS).
Periodic Limb Movement Disorder (PLMD): Characterized by involuntary leg movements (PLMS) during sleep that disturb sleep quality and may affect a bed partner.
Insomnia: Persistent difficulty falling asleep or staying asleep.
Parasomnias: Abnormal behaviors during sleep, such as sleepwalking or night terrors.

Sleep studies can also be used to monitor a person’s response to treatments or therapies, particularly for conditions like sleep apnea, where continuous positive airway pressure (CPAP) therapy may be used.

2. Types of Sleep Studies

There are different types of sleep studies based on the nature of the suspected sleep disorder and the environment in which the study takes place. The most common types include:

Polysomnography (PSG): The most comprehensive sleep study, which involves monitoring a variety of physical parameters during sleep, including brain activity (EEG), heart rate (ECG), muscle activity (EMG), eye movements (EOG), oxygen levels (pulse oximetry), and airflow. This is usually conducted in a sleep center or hospital.
Home Sleep Apnea Test (HSAT): A simplified version of the PSG that focuses on breathing and can be conducted in the comfort of your own home. This test is typically used to diagnose sleep apnea, particularly in patients who are suspected of having moderate to severe sleep apnea and do not have significant comorbid conditions. The test involves wearing sensors that track your breathing, oxygen levels, heart rate, and other variables while you sleep.
Multiple Sleep Latency Test (MSLT): Used to diagnose narcolepsy and excessive daytime sleepiness (i.e., idiopathic hypersomnia), this test measures how quickly you fall asleep during several daytime naps.

Each of these studies provides valuable information, but the level of detail and the equipment used may differ based on your condition and the doctor’s recommendations.

3. Preparing for a Sleep Study

Proper preparation is key to ensuring the sleep study yields accurate and useful results. Here’s how you can prepare for your sleep study:

Before the Study

Talk to Your Doctor: Your doctor will provide specific instructions based on your sleep study type. Follow all advice and disclose any medications or supplements you’re taking, as certain substances can affect sleep patterns. In many cases, you may be asked to avoid caffeine or alcohol before the study.
Dress Comfortably: Wear loose, comfortable clothing to your appointment. You’ll be wearing the sensors, so tight or restrictive clothing isn’t necessary.
Hair and Skin: The night before your sleep study, you may be asked to wash your hair thoroughly but avoid using any hair products such as gels, hairsprays, or oils. These can interfere with the electrodes and sensors. Make sure your skin is clean and free from oils, lotions, or makeup to ensure proper electrode adhesion.
Arrive Early: You’ll typically be asked to arrive in the evening, usually between 7:00 PM and 9:00 PM, depending on the clinic’s schedule. This allows time for the technician to attach all the necessary sensors and equipment.

For Home Sleep Studies

If you're using a home sleep apnea test, your doctor will provide specific instructions on how to set up the equipment. The sensors will likely include a nasal cannula or sensor to monitor airflow, a pulse oximeter to track oxygen levels, and one or two belts to monitor chest and abdominal movements. You will be asked to wear the sensors overnight and return them the next morning for analysis.

4. What Happens During the Sleep Study?

A sleep study is typically conducted in a sleep center or clinic, where the environment is designed to replicate a normal bedroom setting while still allowing for close monitoring. Here’s a step-by-step breakdown of what to expect during the study:

Arrival at the Sleep Center

Once you arrive at the sleep center, you’ll be shown to a private room that resembles a hotel room. The room will usually have a comfortable bed, a bathroom, and the necessary equipment for the study. You may also be given a questionnaire to record any sleep-related notes or concerns.

Sensor Placement

A trained sleep technician will place electrodes and sensors on your body to monitor your sleep stages, brain activity, breathing, and other physiological data. These are typically attached as follows:

EEG (electroencephalogram): Electrodes placed on your scalp to monitor brain activity.
ECG (electrocardiogram): Electrodes placed on your chest to monitor heart rate and rhythm.
EMG (electromyogram): Electrodes attached to your chin and legs to track muscle activity and movements.
EOG (electrooculogram): Electrodes placed around your eyes to monitor eye movements.
Pulse Oximeter: A small clip placed on your finger to measure blood oxygen levels.
Chest and Abdominal Belts: To monitor your breathing and chest movements.
Nasal Cannula: A small device placed under your nose to monitor airflow.

Although it may feel a bit uncomfortable at first, the technician will ensure everything is positioned correctly. The process of sensor placement usually takes around 30 minutes to an hour.

Sleeping During the Study

Once the sensors are in place, the technician will leave the room, and later you will be asked to go to sleep. The goal is to observe your natural sleep patterns, so you’ll be encouraged to sleep as you normally would at home. The technician will monitor you from another room, but they will be able to adjust the equipment and communicate with you if necessary. If needed, it is possible to use the restroom.

It may take some time to fall asleep due to the equipment, but many people eventually adapt to the sensations. The sensors are non-invasive, and while they can feel slightly restrictive, they are generally not painful.

Monitoring and Data Collection

As you sleep, the sensors will collect data on various parameters such as:

Brain waves (sleep stages): Helping the doctor identify any disruptions in your sleep cycle.
Heart rate and rhythm: To check for abnormalities.
Breathing patterns: To identify interruptions in airflow or signs of sleep apnea.
Leg movements: To check for conditions like periodic limb movement disorder or parasomnias.

The technician will continue to monitor your sleep throughout the night. If any issues arise, such as difficulty breathing or severe disruptions in sleep, the technician may adjust the equipment or wake you briefly to re-position things or to initiate treatment.

5. After the Sleep Study

Once the study is complete, typically in the morning, the technician will remove all the sensors, and you’ll be free to leave. If the sleep study is conducted in a clinic, you may be able to leave immediately after, or you may be asked to stay for a brief debriefing. If it’s a home study, you’ll return the equipment the next day.

The data from the study will be analyzed by a board-certified sleep specialist or a doctor. Depending on the findings, your doctor may diagnose you with a sleep disorder or recommend further tests or treatments.

6. Results and Next Steps

After the sleep study, the results are typically available within a week or two. Your doctor will review the data and schedule a follow-up appointment to discuss the findings, which may be delayed further depending on availability. Based on the results, possible next steps may include:

Diagnosis of a Sleep Disorder: If a disorder like sleep apnea, PLMD, parasomnias, or narcolepsy is diagnosed, the doctor will discuss treatment options, including lifestyle changes, CPAP therapy, medications, or referrals to specialists.
Further Testing: In some cases, such as with an inconclusive result, additional tests may be necessary for a more comprehensive diagnosis.
Treatment Recommendations: For conditions like sleep apnea, you may be fitted for a CPAP machine or other devices to improve breathing during sleep.

Conclusion

A sleep study can seem intimidating, but it is a safe and effective way to diagnose sleep disorders. By understanding what to expect, you can enter the study feeling prepared and more at ease. Whether you’re undergoing a comprehensive polysomnography in a sleep center or using a home sleep apnea test, the process is designed to provide critical information that will help your doctor assess your sleep patterns and recommend appropriate treatment options. By diagnosing and addressing sleep disorders, sleep studies can significantly improve your quality of life, leading to better rest and overall health.