Sleep studies are tests performed in a sleep center that measure physiological aspects of sleep. They are typically performed in a sleep center, and are used to diagnose sleep disorders including insomnia, hypersomnia, sleep apnea and narcolepsy.

A number of activities are measured during a sleep study, such as electrical activity of the brain and heart, oxygen saturation and leg muscle movement.

Before the sleep study, patients may be required to maintain a sleep diary in which they record their sleep patterns. Some ways to prepare for the study are avoiding alcohol and caffeine and packing a bag with personal items needed for an overnight stay.

During the sleep study, electrodes and other sensors are usually placed on the scalp, sides of the head and under the chin, chest and legs. A sensor is typically placed under the nose and mouth and belts are placed around the chest and abdomen. A clip is placed on a finger.

Patients go to sleep and are monitored throughout the night by a technician and video cameras. After the study is completed, the results are tabulated and may be sent to the physician or other health professional who referred the patient to the sleep center.

A sleep study is a series of tests that measures physiological aspects of sleep in an effort to diagnose sleep disorders. It is usually conducted in a sleep center and is  indicated when a patient experiences non-restorative sleep. Sleep studies may be performed for patients who have trouble falling asleep or staying asleep (insomnia), have an excessive need for sleep (hypersomnia), or have other conditions that may affect their ability to sleep, such as restless legs syndrome.

Many people also undergo sleep studies because it is suspected they may have  sleep apnea, a condition in which they stop breathing multiple times during the night. For instance, children with conditions such as Down syndrome and Prader-Willi syndrome (a rare condition characterized by chronic hunger and overeating) may benefit from sleep studies as sleep apnea and abnormal sleep patterns are very  common among these populations.

Sleep studies can measure the stages of a person’s sleep cycle in addition to many physiological activities that occur during sleep. Patients do not usually experience discomfort while tests are being performed.

The physiological measurements of a sleep study may include:

• Electrical activity of the brain (electroencephalography or EEG). Performed by placing electrodes on the scalp. An EEG can identify the specific stages of sleep and any disturbances, which may help diagnose a specific sleep disorder.
  
  
• Respiratory effort. Two bands are placed around the chest and abdomen to monitor movements while breathing, and measurements are made electronically.
  
  
• Airflow. Performed with electrical sensors placed just under the patient’s nose.
  
  
• Oxygen saturation. Performed using a pulse oximeter, a device placed on the patient’s finger or earlobe that measures the oxygen level in the body.
  
  
• Eye movement (electro-oculogram or EOG). Performed by placing electrodes on the face near the eyes.
  
  
• Muscle movement (electromyography or EMG). Performed by placing electrodes on legs and usually on the chin.
  
  
• Electrical activity of the heart (electrocardiogram or EKG/ECG). Performed by placing electrodes on the chest.
  
  
• Body position. The patient’s body positions throughout the night are recorded on video and monitored.
  
  
• Volume and frequency of snoring. Audio recordings of patients’ snoring are sometimes taken during a sleep study.

From the physiological information obtained, physicians can better understand aspects of sleep including how much time patients spend in each sleep stage, how often they wake up and how their breathing changes or stops during the night. Some unusual behaviors (e.g., sleepwalking) may also be observed, although these may not occur in a single sleep study.

Physicians use the sleep study information to diagnose certain sleep disorders, including:

• Insomnia. Difficulty falling asleep or staying asleep, resulting in inadequate length of sleep and/or poor quality of sleep.
  
  
• Hypersomnia.  An unexplained increased need for sleep.
  
   
• Sleep apnea. A disorder in which a person’s breathing stops and starts many times during sleep. Snoring is a common symptom of sleep apnea.
  
  
• Narcolepsy. A neurological sleep disorder characterized by sudden and uncontrollable sleepiness and frequent daytime sleeping.
  
  
• Restless legs syndrome. Sleep disorder characterized by unpleasant sensations in the legs that are described as creeping, crawling, tingling, pulling or painful.

The most common types of sleep studies include:

• Overnight polysomnograms. Tests that are conducted during the night hours, usually in a sleep center. They monitor physiological activity while patients sleep.
  
  
• Multiple sleep latency test (MSLT). Conducted in a similar method as a polysomnogram, but performed during daytime hours. The test is conducted to determine how quickly a person falls asleep during daytime hours, usually for several 20-minute naps.
  
  
• Maintenance of wakefulness tests (MWT). Measure a patient’s ability to remain awake in a dark and quiet environment.

Before the sleep study is conducted, patients may be asked to keep a sleep diary. They may record bedtimes and waking times, number of hours slept and number of arousals during the sleep period.

Patients may be asked to discontinue taking some medications if it is believed that the drugs will interfere with study results. Other ways patients may be instructed to prepare for the study include:

• Maintain regular sleeping patterns in the days prior to the study to ensure natural sleep during the study.
  
  
• Refrain from eating foods or drinking beverages that contain caffeine, such as chocolate, soft drinks and coffee, because they may interfere with sleep.
  
  
• Avoid alcohol, stimulants, sedatives or other types of medications or substances that may disrupt sleep.
  
  
• Pack a bag with personal items necessary for an overnight stay (e.g., pajamas, toiletries and change of clothing).
  
  
• Take a shower or bath before the study, but do not apply oils, gels or sprays to the hair because it may prevent electrodes from sticking to the hair.
  
  
• Remove nail polish from at least two fingers to avoid problems with the pulse oximeter (device placed on a finger that measures blood oxygen levels).
  
  
• Do not wear makeup to avoid problems with electrodes on the face.

Sleep studies are usually conducted by trained sleep lab technicians during late evening and early morning hours. Patients are typically instructed to  arrive a few hours early to prepare for the study. Patients may be asked to fill out a questionnaire about their sleep patterns, including the amount and quality of sleep experienced during the previous night.

After changing into night clothes, patients settle into bed in a private room similar to a hotel room. Electrodes are usually placed on the scalp, sides of the head and under the chin, chest and legs. A sensor is typically placed under the nose and mouth and belts are placed around the chest and abdomen. A clip is placed on the finger. These devices record physiological activity. Most people have no problem falling asleep or staying asleep with the monitoring sensors in place. Technicians located in another room collect data and observe sleep with a television monitor.

Patients may be asked to perform certain tasks after the sensors have been placed on the body to determine whether they are working properly. The lights will be turned off and the patient falls asleep.

With some patients, a split-night test is conducted. Half of the night is used to diagnose the sleep disorder and the other half is used to treat it. This occurs most commonly in cases of sleep apnea.

The following morning, patients may be asked to fill out a questionnaire describing the sleep experience the previous night.

After the results of the sleep study are collected, they are sent to the physician or other health professional who referred the patient to the sleep center. Physicians may diagnose a sleep disorder based on the results of the study.

Sleep disorders are often diagnosed after a single visit to a sleep center. However, some patients may have to return to the sleep center for additional testing. For instance, recent research shows that a negative test for sleep disordered breathing in children may have to be repeated in order to rule out a problem definitively. Additionally, many patients become more comfortable with the testing equipment and procedures employed during subsequent visits to the sleep center. This results in more natural sleep and more accurate study results.

After a sleep study, patients may receive a variety of treatments depending on the type of sleep disorder diagnosed. Sleep disorders in some patients can be treated by making simple lifestyle modifications, such as maintaining consistent sleep and wake times, avoiding alcohol and caffeine before bed and exercising. Other patients are treated with medications, such as the newer non-benzodiazepine sedative-hypnotics.

Other techniques that may be used to treat sleep disorders include:

• Relaxation therapy. Methods such as progressive muscle relaxation, deep breathing techniques, imagery and self-hypnosis may help some people overcome sleep disorders.
  
  
• Cognitive behavior therapy (CBT). This may help patients identify thoughts and behaviors that contribute to sleep problems.
  
  
• Continuous positive airway pressure (CPAP). Device used to treat sleep apnea. It involves wearing a mask over the nose that blows air into the throat at a pressure level appropriate for the patient.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following sleep study-related questions:

1. Might I benefit from a sleep study?
   
   
2. Can you recommend a sleep study facility?
   
   
3. How should I prepare for a sleep study? Should someone come with me?
   
   
4. What physiological functions will be measured during my sleep study?
   
   
5. What sleep disorders may be diagnosed after my sleep study?
   
   
6. What happens if I have trouble sleeping during the sleep study?
   
   
7. Will the tests performed during my sleep study be uncomfortable or painful?
   
   
8. What will happen after I get the results of my sleep study?
   
   
9. Can I return to my normal daily activities following my sleep study?
   
   
10. How long before the sleep study results are available? How will I learn of the results?
    
    
11. Will I need to undergo repeat sleep testing? If so, how often?