A sleep study provides detailed information about the unique physiology of sleep which is instrumental in the evaluation of sleep and the diagnosis of sleep disorders.
During the sleep study, electrodes and sensors are non-invasively attached for recording the electrical activity of the brain and muscles as well as for recording breathing, oxygen levels, and heart rate during sleep.
The patient concerns about why a sleep study is needed, what happens if you have trouble sleeping during the study and safety of the procedures are discussed in the article.
The goal of the sleep evaluation is for an accurate diagnosis and the determination of effective treatments for a sleep problem. (1) Given the current conditions of COVID-19 many sleep centers are not open. In this case a home sleep test is the only option.
If you have trouble with your sleep or you feel drowsy during the day even after a full night’s sleep, you are not alone. Several large surveys in recent years have shown that up to one third of the population has significant difficulty with sleep. Sleep disorders can affect everyone from babies to the elderly.
But why do we care about poor quality sleep or too little sleep? There is a common misconception that missing a few hours of sleep is really not all that important, and at worst it is a minor inconvenience. However, poor sleep and daytime drowsiness have been linked, among other problems, to increased numbers of automobile accidents, poor work and school, performance, diabetes, heart disease, high blood pressure, and depression. Thus, poor quality sleep and too little sleep make us vulnerable to a decrease in our quality of waking life. If your sleep has begun to interfere with your health and quality of life, your doctor may refer you to a Sleep Center for an overnight study in order to discover the cause of your symptoms. The purpose of this article is to give you a description of what occurs during these studies.
You may see the terms polysomnographic evaluation or nocturnal polysomnogram used in referring to an overnight sleep study. In a nutshell, a polysomnographic evaluation consists of recordings of your brain and bodily activity during a study sleep which is performed overnight in a Sleep Center. (2) Polysomnographic evaluations provide detailed, invaluable information about the activity of the body and brain during sleep that cannot be discovered during waking as the result of major physiological changes during sleep. These changes can be associated with disorders that are unique to sleep. We all know how sleepy, drowsy, and out of sorts we feel during the day if we do not get a good night’s sleep. So really the purpose for sleep is not just to sleep at night, but to ensure our overall health and optimal functioning during the day.
Full polysomnographic monitoring, which we discuss in detail later, is the “gold standard” for the diagnosis and treatment of sleep disorders. (3) Recently, new technology has been developed to allow limited polysomnography to be performed with portable monitoring devices which are worn at home. (4) There are advantages and disadvantages to both types of monitoring, and the details of portable monitoring studies are discussed in a separate article. (5)
Before we discuss the details of what happens during a sleep study, let’s address some very general questions that you may immediately have when you are first referred to a Sleep Center.
If your doctor suggests that you prepare for a sleep study, your initial reaction may be “Why do I even need a sleep study? I’m a little sleepy during the day, but I don’t have any trouble sleeping at night. My sleep is fine!”
After you ask this question, remember that when you are asleep, you are the most unreliable of observers as to what your body is doing and to your behavior during your sleep. It is very obvious, but the reason you are not a good witness is that you are asleep! For example, patients commonly deny that they snore loudly. Sometimes this snoring is so loud that it wakes up every person, and even pets, in the household. However, the sleeper remains blissfully unaware of these loud, disruptive sounds. It seems even more unbelievable that your bed partner might tell you that, besides loud snoring, you stop breathing during sleep over and over throughout the night. Sometimes these periods last only a few seconds, but often they last 30 to 60 seconds or even louger. You are probably thinking, how is it possible to snore so loudly and to stop breathing during sleep without even being aware of this? It is precisely because you ARE asleep that you do not have direct knowledge of your bed partner’s observations. This is why the overnight polysomnographic evaluation becomes an essential tool for discovering precisely what is occurring in your body during sleep.
Another immediate concern that you may have is whether you will be able to sleep during your study.
The thought of spending the night in a new environment with a multitude of recording electrodes and sensors attached to your head and body while you are being observed and heard on a closed circuit monitoring system throughout the night is enough to cause distress and anxiety among even the bravest person. The circumstances surrounding a sleep evaluation are so remarkably different from our usual sleeping experience at home that it may seem as though no one could possibly sleep normally under these conditions.
It is common to have some difficulty sleeping in a new and unfamiliar environment. Almost everyone has had the experience of staying in a hotel room and then having some difficulty falling asleep. In fact, there is a phenomenon called the “first night effect” which has been studied in persons sleeping for the first time in new environments. However, some minor difficulty falling asleep in a new place due to nervousness or anxiety is normal and does not mean that the results of the sleep study will be invalid. Not having your completely usual sleep such as you have at home still allows, in most cases, for a sleep disorder, if present, to be recognized and treated. Sometimes, the sleep doctor will order a home sleep study to evaluate for sleep apnea.
One important note, however, is that if you are having difficulty falling asleep because the recording devices are causing you discomfort, be sure to call the technician so the monitoring devices can be adjusted. This does not mean that the sensors can be removed since they all record important information for diagnosing your sleep problem. However, the technician can typically make adjustments for greater comfort so that you can sleep.
You may be surprised at how well you sleep under the conditions of the sleep study. The majority of patients usually do not have as much difficulty sleeping as they anticipate, and almost everyone sleeps enough during their study to make an accurate diagnosis. In fact, it is not unusual for patients to report that the quality of their sleep is even better during their study than it is at home. If your sleep problem has become debilitating, you may feel relieved that the source of your sleep problem is finally being directly examined with specialized testing, thus decreasing your concern about not sleeping. Sleeping medications are typically not provided by the technicians on the night of study, but in some circumstances the use of medications will be discussed with you by the sleep specialist prior to your study.
Most patients spend one or sometimes two nights in the Sleep Center and in some cases a series of daytime nap tests called the Multiple Sleep Latency Test, referred to as the MSLT, may be performed during the day following the overnight study. In addition, depending upon the results a “split night” study may be performed for further evaluation of sleep apnea (stopping breathing during sleep). However, this will be discussed with you in advance of your study.
Probably the single most important factor in allowing yourself to fall asleep during your evaluation is to keep a positive mindset and focus on the benefits that you will obtain as the result of the information which is being collected. Remember that the results will provide you with detailed and important information about the cause of your trouble with sleep which will, in turn, lead to potentially effective treatment. If you feel as though you are having trouble falling asleep, try thinking about these positive benefits and relax your body with deep breathing and muscle relaxation to encourage sleep.
Finally, remember that the technical staff can hear and see you at all times during the night should you have any difficulty or concerns. In most Centers, all you have to do is speak and the technician will enter the bedroom to help you.
Now that we have addressed these initial concerns, let’s discuss what happens before your study, during your study and after your study. Of note is that there may be some variation in these procedures depending upon the Sleep Center. Always check with the Sleep Center where you are scheduled if you have questions.
You will be asked to make some preparations before you report for your evaluation so that the most accurate information about your sleep can be obtained. Again, check with the Center where you are scheduled if you have questions..
You will be asked to report to the Sleep Center two hours or so prior to your bedtime in order to prepare the equipment and attach the recording sensors and equipment to your body. It is important to report at your assigned time so that there is enough time to prepare you for the night and so that you spend at least six hours in bed. Very short times in bed may not allow for enough sleep to determine a diagnosis.
You will sleep in a private bedroom where the study is performed. All of the actual monitoring equipment is in a separate room. After you have changed into your pajamas, a technician will come into your room and begin applying the electrodes and sensors for your recording.
Is it painful to have these electrodes and sensors applied? The answer is no. The technician attaches each of the electrodes and sensors to the surface of your skin and to your scalp with cotton gauze and/or surgical tape after cleaning. If you experience any irritation as the technician cleans your scalp and skin, be sure to speak up. None of the recording devices break the skin, and none are placed beneath the skin. If you have a known allergy to tapes, be sure to let the technician know in advance.
Although there can be variations in the types of sensors which are used, during most sleep evaluations the following recordings will be made.
Some patients, in addition to these sensors, will also have a mask which covers the nose or the nose and mouth, depending upon the circumstance, for further evaluation of sleep apnea. This mask carries pressurized air from a machine and through the mask in order to keep the throat open and breathing regular. This device is a continuous positive airway pressure (CPAP) machine. Your sleep specialist will discuss whether or not CPAP will be used during your evaluation with you before the study.
“There is so much equipment attached to me! Is it safe? One concern that you may have is whether the recording sensors and equipment are safe. Nothing is passing into your body from the recording electrodes, sensors, or any other equipment. The equipment is safe. There are electrical safety checks and equipment inspections routinely performed in the Center to ensure patient safety. The tiny electrical potentials generated by your brain and muscles are being magnified and passed through your electrodes into the monitoring room recording devices.
After the sensors are applied, a process which typically takes about an hour, you will probably be allowed to read or relax until just prior to the time that you usually go to bed.
All of the equipment which is used to record the activity of your body during sleep is housed in a monitoring room separate from your bedroom. Your bedroom should be quiet. No radios or television will be left on during the study. This is so that the technician can hear you clearly, and so that your sleep is not disturbed. There is a closed circuit television system which will allow the technician to see you and talk to you from the monitoring room. The technician will be continuously observing you and monitoring your recording throughout the night. Also be aware that the technicians are trained in cardiopulmonary resuscitation (CPR) and the Sleep Center has procedures for implementing emergency medical procedures.
Starting the sleep study. When your bedtime arrives, the technician will ask you to lie down in bed, and your recording devices will be connected to a specialized recording box which is in turn attached to a cable going into the recording equipment in the monitoring room. To start the sleep study the technician will talk to you over the two-way intercom system. You will be asked to perform a series of maneuvers in order to test the electrodes. For instance, some of these instructions typically include opening and closing your eyes, moving your eyes, sticking out your tongue, flexing your legs, and holding your breath. By following the instructions, the technician can make adjustments to the recording and to be sure that all of the sensors are operating correctly. You will then be asked to try and fall asleep. At this point the study has begun.
Getting up during the night. If you need anything during the night, you can speak and the technician will hear you in the monitoring room. Many persons get up during the night to use the restroom. It is a simple procedure for the technician to get you up, and the electrodes are not removed when this occurs. If you need to use the restroom or need anything else, call the technician and your electrodes will be “unplugged” from the recording cable. You should not try to detach yourself and get up without notifying the technician.
Before your study begins, the technician will ask you at what time you want to get up in the morning. You will usually be scheduled to spend at least six hours in bed during the sleep test. After you are woken up and out of bed, the technician will remove the recording sensors, and you will be asked to complete a brief questionnaire about how you slept during the study. You will then be free to leave the Center.
The recordings of your sleep will be scored for sleep stages as well as for any breathing abnormalities or movement events. Standardized rules published by the American Academy of Sleep Medicine are used for scoring sleep studies. After scoring, the records, along with your sleep and medical histories, will be reviewed by a board certified sleep specialist, and a report which contains the results and treatment recommendations will be generated. The report will be sent to your referring doctor who may give you these results or you may be scheduled to return to the Sleep Center for discussion with the sleep specialist.
Sleep Centers which are accredited by the American Academy of Sleep Medicine (AASM) have passed rigorous safety and technical standards in order to perform high quality sleep studies. Sleep specialists who have passed examinations leading to board certification in sleep medicine are affiliated with these Centers and are qualified to interpret the sleep study as well as to provide treatment recommendations. In addition, technicians employed by these Centers are typically board certified by the Board of Registered Polysomnographic Technologists (BRPT). This accreditation ensures that the technicians adhere to high standards for patient monitoring and that they are certified in emergency cardiopulmonary resuscitation (CPR) procedures. Just as you would choose a board certified physician for your usual medical care, choosing an AASM accredited Sleep Center for your sleep care will ensure that high quality standards are being used to diagnose your sleep disorder. For a list of board certified sleep physicians, visit the website of the American Board of Sleep Medicine.
You can see from this review that a polysomnographic sleep study evaluation is a detailed, comprehensive process. Although it may seem complex, it is not a difficult study for you, the patient, to have performed. All you have to do is lie back, relax, and sleep. What other medical test have you had in which the primary requirement was to sleep, and how much easier could a test be? Anticipate having a great night during your evaluation!
Further readings on sleep studies
Polysomnography by Carmel Armon, M.D.at http://emedicine.medscape.com/article/1188764-overview
No more sleepless nights (revised edition) (book)
Peter Hauri, Ph.D. and Shirley Linde, Ph.D.
John Wiley and Sons, 1996
The mystery of sleep: Why a good night’s rest is vital to a better, healthier life (book)
Meir Kryger, M.D.
Yale University Press, 2017.
Author: Kristyna M. Hartse, Ph.D.
Diplomate, American Board of Sleep Medicine (ABSM)
Fellow, American Academy of Sleep Medicine (AASM)
Registered Polysomnographic Sleep Technologist (RPSGT)
Registered Sleep Technologist (RST)
Certification in Clinical Sleep Health (CCSH)
© 2021 American Sleep Association.