How a Sleep Study Works, and What You Gain From It

In this article, we will explain the process of a sleep study, as well as list some good reasons for getting examined early on, and what you can do to make the doctors’ jobs easier

Written by:

Tamara Smith

, Sleep Researcher
Last Updated: Wed, October 2, 2019
Fact checked by:

Marko Jevtic

, Sleep Specialist

If you’ve been reading our website for some time, you are probably aware of the multitude of sleeping disorders that seemingly lurk around every corner. We wouldn’t put it past you if you started believing that many lifestyle habits people consider normal can lead to sleep problems and compromise your health by weakening your immune system through fatigue. To make matters worse, many of these sleep disorders and issues are hard to identify when you’re on the receiving end, as it’s quite easy to take symptoms for granted and treat them as just a part of life.

If you ever run into a situation where you suspect you’re dealing with a sleeping disorder or regularly experience sleep problems, the single best course of action is visiting your primary care physician for initial tests and questioning. A quick examination is often only a starting point – if they notice anything worrying, you may be put through further examinations that determine what causes your sleeping problems. In this article, we will explain the process of a sleep study, as well as list some good reasons for getting examined early on, and what you can do to make the doctors’ jobs easier. Let’s get into it.

The First Diagnostic Stage

The rule of thumb is obvious – as soon as you notice regular sleeping problems, schedule an appointment with your doctor. If something is preventing you from seeing them this early, start keeping a sleep journal. A sleep journal can be a simple notebook where you write down details about your sleeping habits. A full-scale sleep study often involves a sleep journal, so you want to make sure you have something to present as soon as possible. Even if you don’t start at this point, your doctor will tell you to start once the first examination is done (assuming you pass the screening tests, more on that in a bit).

If you want to be helpful to them, you want to use your sleep journal notebook to document various pieces of information about your sleep. For example, they may want to know things like:

–          When you go to sleep and when you wake up

–          How long it normally takes you to fall asleep once you’re in bed (this is commonly known as sleep onset latency, and it’s often measured if you’re dealing with suspected narcolepsy or similar disorders)

–          How tired you feel when you wake up and right before bed (not necessarily in the late evening and morning – some disorders change when your body wants to go to sleep)

–          How often and when you wake up during the night. Fragmented sleep is a huge health concern, as it stops your body and mind from recovering properly during the last two stages of sleep.

–          How exhausted you feel during the day – fatigue makes you perform worse in most aspects of life, especially work and driving.

–          How often you consume alcohol and caffeine

When you visit your doctor for the first time and explain your problems, they may give you a questionnaire or two to fill out. These questionnaires are usually the first stage of sleep diagnosis and include tests like the Pittsburgh Sleep Quality Index or Epworth Sleepiness Scale. Each answer in these questionnaires carries a score that gets added up towards a final result. If you pass a certain threshold at the end, it serves to indicate the presence of a possible sleep disorder. These tests are often used as a sort of screening filter for early patients. If the result of these tests shows no signs of a sleep disorder, then the problem is often classified as a lifestyle thing, and no real further examination is done aside from basic blood and urine sample analysis.

Expect to be asked a variety of questions about your daily life. Sleep problems can appear as a result of many seemingly unrelated habits and situations, so you want to give the doctor as much information as you can, even about things that don’t normally appear in a sleeping journal. If you’ve been maintaining a sleep journal or using other sleep tracking devices, it can speed up the diagnostic process and skip you right to the next phase – a full polysomnography procedure, or what is known as a “sleep study.”

How Does Sleep Studies Work?

The most common diagnostic technique or procedure used during a sleep study is polysomnography, to the point where the two terms are used interchangeably. Polysomnography is a thorough, detailed investigation into the patient’s sleeping patterns, looking at how their body behaves throughout a full night of sleep, as well as performing additional lab tests with blood and urine samples. In most cases, this procedure will involve reading the person’s sleep journal notes (or information provided by sleep tracking apps and devices, depending on what was agreed upon in advance and what the patient could afford). The information from previous examinations (including questionnaires like the Epworth Sleepiness Scale) also proves handy at some point. Here’s a step-by-step overview of what happens during a sleep study:

–          Before you even show up to the sleep lab, you will be given diet instructions. In simple form, these instructions boil down to avoiding alcohol, caffeine, sugary or greasy food, and anything that could produce “false alarm” readings or otherwise interfere with the results of the sleep study. The longer you maintain this preparation diet, the more accurate the readings will be, so stay disciplined.

–          Make sure you clear your schedule for days that immediately precede and follow the sleep study. Because this is a procedure that takes a whole night, you don’t want your work schedule or similar obligations to interfere with the procedure.

–          Most of the time when you arrive at the sleep lab (the place where sleep studies almost always take place), they will do a basic examination and explain the whole procedure to you (if your doctor didn’t already do that before). If you have a sleep journal prepared, which you should, you will be given a chance to present it and will often have to fill another questionnaire to make sure the results sync up with the previous examinations. Most sleep disorder-related questionnaires can easily be repeated multiple times in a short period, and it helps avoid biased answers and forgetfulness.

–          Once all of this is done, you will be hooked up to devices that monitor your bodily functions, usually after making sure that your sleep surface is comfortable. Electrodes will get attached to various spots on your body, and you will be constantly watched by sleep technicians and other specialists. Overall, the information that is tracked varies depending on what the technicians expect to see. If they suspect the presence of seizures, additional electrodes will be attached to you to keep track of seizure activity. The lights will get turned off, and the technicians will use low-light cameras to monitor your behavior. You can talk to each other if the need arises, but they will avoid interrupting your sleep whenever possible.

–          While you sleep, the experts will keep track of your heart rate, breathing patterns, brain wave patterns, nocturnal eye movement, the shifts in your sleeping positions, etc. All of this information is relevant because specific sleep disorders have specific “tells” that are crucial to making a correct diagnosis. For example, eye movement and brain wave patterns are important for detecting the REM stage of sleep, the stage where vivid dreams occur and a lot of brain activity resembles that of a waking person. Certain disorders affect this stage and are hinted at by abnormalities in the patient’s sleep architecture (the natural progression between sleep stages). Breathing patterns are essential for diagnosing problems such as obstructive sleep apnea, and so on.

–          You will usually be discharged around 7 am, and the results of this procedure are usually sent directly to your doctor for when you show up for a follow-up examination.

Overall, there’s nothing to be nervous about. No part of this procedure hurts or has any harmful consequences, so you shouldn’t worry. Even though you’re sleeping in a different bed (and could thus take extra time to adjust and find a comfortable position), the machines are accurate enough to nullify that detail.

The Follow-Up and Multiple Sleep Latency Test

Depending on what your doctor suggests beforehand and what they notice during the sleep study, you may be put through the Multiple Sleep Latency Test (MSLT) during the day following the polysomnography. This test is an incredibly common diagnostic technique for many disorders, and its purpose is to measure excessive daytime sleepiness and average sleep propensity. The procedure is incredibly simple and resembles a “smaller” version of a full sleep study. The idea is that the more daytime sleepiness a patient faces, the easier it is for them to doze off and start napping. The MSLT procedure involves the patient trying to take a nap multiple times during the day, usually around four times a day.

The napping periods last 20 minutes and are separated by breaks of two hours each. The less time it takes for the patient to fall asleep during each napping period, the more excessive daytime sleepiness (or daytime fatigue) they’re exposed to, on average. Obviously, external conditions can affect their level of fatigue, but the results are consistent with whatever ends up being diagnosed through a full sleep study.

Universal Treatment Advice

Most sleep disorders lack a proper cure. The prescribed therapy plan typically revolves around alleviating symptoms, and your doctor will offer lifestyle advice and similar recommendations to help you improve your quality of life while dealing with a sleeping disorder. For example, sleep apnea is dealt with through the use of positive air pressure (PAP) generator, but that doesn’t make the sleep apnea go away completely – it only helps you sleep better during the night. A lot of lifestyle advice you receive will sound the same regardless of which specific condition you’re facing. Here’s a list of steps you can take to improve your sleep quality in general:

–          Improve your diet. Much like how you have to spend a week avoiding unhealthy foods before a sleep study, train yourself to avoid sweets, greasy food, alcohol, carbonated drinks (especially energy drinks), etc. A good diet plan helps you in more ways than just through improved sleep.

–          Introduce regular exercise into your daily or weekly routine. If you’re out of shape, it’s definitely not unacceptable to start slow, and only work out once or twice per week. Exercise not only helps you develop your body (when maintained over a long period of time), but the resulting increase in sweating helps you remove toxins, which helps you relax when you need to relax the most.

–          Keep working on your sleeping journal. Eventually, you will have to get re-examined by your doctor, and the new information can be incredibly helpful for monitoring the treatment plan. If your sleep patterns improve, it will be obvious in the journal, and the doctors can recommend subtle adjustments that help you even more.


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