Measuring Sleepiness for Diagnostic Purposes

In this article, we will list off the most commonly used diagnostic methods for measuring sleepiness, and explain how they work and how credible they are.

When it comes to diagnosing sleep disorders, it’s important to get an insight into how the patient spends their days – and their nights. Daily fatigue is a common symptom of a variety of conditions, with a prominent example being excessive daytime sleepiness (EDS), among others. Therefore, if we can learn how sleepy a patient feels during the day, we can trace that fatigue back to its most probable cause and offer them an accurate diagnosis and treatment.

The inherently subjective nature of some of these sleepiness quantification methods has been brought into question many times in the past. It’s easy for a patient to unintentionally misremember or exaggerate the severity of their symptoms when filling out a questionnaire. However, as subjective as their statements can be, the diagnosis success rate involving these sleepiness quantification methods continues to prove their effectiveness as a diagnosis tool. Additionally, their ease of use and accessibility make them easy to implement at various clinics and research centers, even if the budget doesn’t have room for more technologically advanced equipment.

In this article, we will list off the most commonly used diagnostic methods for measuring sleepiness, and explain how they work and how credible they are. Let’s get into it, one by one:

Pittsburgh Sleep Quality Index

Developed during the 1980s in the University of Pittsburgh’s Western Psychiatric Institute and Clinic, this diagnostic resource was created to prove a connection between psychiatric conditions and sleep disorders, the idea being that the sleep disorders can often occur as a direct consequence of a psychiatric condition. The development of the Pittsburgh Sleep Quality Index (or PSQI for short) is largely attributed to the work of Dr. Daniel J Buysse.

The PSQI is used primarily as a preliminary test to determine whether a patient requires more thorough and detailed sleep investigation, typically through the use of a polysomnogram. Part of what makes this tool accessible is the fact that no one involved needs any formal training, meaning you can potentially fill it out at home by yourself. It’s also not a time-consuming test, as the whole process takes around 5-10 minutes. The test consists of nineteen separate questions that all add up to form scores in seven categories. Here’s a brief list of categories so you can get a better idea of where this is going:

–          Sleep Duration

–          Subjective Sleep Quality

–          Habitual Sleep Efficiency

–          Sleep Disturbances

–          Sleep Latency

–          Daytime Dysfunction

–          Usage of Sleeping Medication

The separation of the results into these categories helps doctors eliminate unlikely illness candidates by understanding where the symptoms manifest in the patient’s daily life, which vastly improves the accuracy of their diagnosis. The Pittsburgh Sleep Quality Index has been incredibly useful at identifying possible sleep disorders (such as primary insomnia), especially in the case of depression-related conditions and self-reported sleeping problems. However, its usefulness as a tool for tracking patient progress during therapy has not been confirmed or praised, and it is quite lacking when diagnosing patients with dementia. The reliability and accessibility of the PSQI have been vital to its status as a frequently used clinical and research tool, and it has been translated into 56 different languages to this day.

Stanford Sleepiness Scale

Originally developed in 1972, the Stanford Sleepiness Scale (or SSS for short) is one of the oldest subjective scales still used to measure sleepiness today. It is very accessible to English-speakers around the world, as they can find it for free online. The process is very simple – the patient selects a value ranging from 1-7, representing how sleepy they feel during the day. The idea is that you can do this test multiple times to verify your level of fatigue, which helps doctors get an insight into your circadian rhythm and daily schedule.

One of the biggest benefits to the SSS is that it reminds the person about their sleep schedule and circadian rhythm very frequently. The fact that they have to fill it out multiple times per day means sleep health is never too far from their mind, and they are then more capable of providing other subjective input to help their doctor come to a good conclusion. Shift workers get extra benefit from this test as it can show them when they’re the most alert and ready to perform during the day. As a result of this convenience, many doctors use the SSS as an extra diagnostic option, coupled with other methods.

Over time, criticisms emerged about the effectiveness and reliability of the SSS. The two major criticisms both focus on the perceived lack of nuance that the SSS operates on. For one, the test does not differentiate between someone with a sleep disorder and a temporarily tired but otherwise healthy person. On top of that, the test implicitly oversimplifies sleep by overlooking all the details that can go into why a person is experiencing daytime drowsiness or similar symptoms. Due to this, it is rarely or never used by itself as a diagnostic tool, and serves more as a way to extract an accurate subjective report.

Epworth Sleepiness Scale

As one of the main diagnostic tools for detecting sleeping disorders, the Epworth Sleepiness Scale (or ESS for short) sees widespread use amongst both clinicians and sleep researchers. The ESS emerged around the early nineties, developed by Dr. Murray Johns at Epworth Hospital in Melbourne. When a patient begins this test, they’re given a questionnaire to fill out. This typically doesn’t take longer than ten minutes to complete, and it doesn’t require any formal credibility from anyone in how it’s used. The questions present common day-to-day situations and ask the patient how likely they are to fall asleep in those scenarios. Here’s the list of situations used for the ESS questionnaire:

–          Sitting and reading

–          Sitting and holding a conversation

–          Lying down in the afternoon

–          Sitting idle after lunch

–          Being a passenger in a car for over an hour

–          Watching television

–          Sitting in a public place, inactive

–          Stuck for a few minutes in traffic while driving

The answers are graded based on a simple point system. If the person is extremely unlikely (to the point where it’s practically impossible) to fall asleep in a given situation, they receive 0 points for that question. The maximum amount of points is 3, indicating that the person is highly likely to doze off at some point. When the test is complete, all the points are added up to a total score. Initially, test subjects with established sleep disorders were given this questionnaire and based on their answers and scores, the score of 10 points was declared an important threshold – people who score 10 or higher suffer from excessive daytime sleepiness.

This score won’t change during a single day, which means it’s not effective at keeping track of a person’s circadian rhythm. However, the ESS is exceptionally reliable as a monitoring tool once a patient starts receiving therapy or using medication. Because of its ease of use and accessibility, it sees common use amongst doctors and researchers alike.

Multiple Sleep Latency Test

The Multiple Sleep Latency Test (MSLT for short) is the most often used diagnostic tool when it comes to sleep disorder detection. It is frequently recommended by doctors everywhere as the results are impossible to misinterpret or get wrong. How it works is, a few weeks before the test, the patient is asked to stop using any medicine that could affect their sleep architecture, such as depressants, anti-depressants or stimulants – even coffee is off limits. Once this demand has been met, thorough polysomnography is conducted to monitor the patient’s sleep for one night. This is done in part to ensure that the patient sleeps at least 6 hours prior to the MSLT.

The next day, the patient comes to the sleep lab where they fill out a simple questionnaire. Depending on the sleep lab and the specific case they’re looking into, they may take blood and urine samples. Once that’s all done, the person either sits in a special chair or lies down on a prepared bed for the important part of the test. Electrodes are hooked up to their face, scalp, and chest, and they are told to take a nap. The napping period lasts about 20 minutes, after which the patient is woken up to recover for a while before trying again.

The idea behind this test is to measure how quickly a patient will fall asleep during “daytime naps” after getting enough rest the previous night. The quicker they fall asleep (the critical threshold is around 5 minutes or less for narcoleptic patients), the more likely it is that they are suffering from excessive daytime sleepiness (EDS). The thing about EDS is that it often comes packaged in with another sleep disorder. The combination of the MSLT results and the previously done polysomnography session is the most precise method we have of making an accurate diagnosis.

Overall, the MSLT is primarily used in diagnostics to detect narcolepsy, periodic limb movement disorder, sleep apnea, and idiopathic hypersomnia. Results are also useful when trying to detect sleep-related seizure disorders. The only downside to this test is the time and money investment it demands. Both the polysomnography session and the MSLT itself are typically conducted at a specialist sleep lab, and take up almost 20 hours combined. If you can afford this method, we highly recommend it.

Fatigue Severity Scale

The Fatigue Severity Scale (or FSS for short) was created in the late 1980s as a tool that can measure how much fatigue affects a patient’s daily waking routine. More specifically, it was made to monitor the fatigue experienced by people who are dealing with multiple sclerosis or systemic lupus erythematosus. The FSS sees use as a secondary tool for various therapy plans and policies, usually for patients with chronic diseases – but often for sleep research as well. Additionally, it’s used when dealing with patients who are afflicted with major depression.

The FSS functions based on a questionnaire (like many other methods in this article). There are a total of 9 questions in the form, each one having seven possible answers. The higher you go, the more strongly you agree with the question statement. Each answer can score up to seven points, and the points are added together at the end. The maximum score is 63 points, and a threshold of 36 points represents the presence of considerable fatigue. Most people who fill in this questionnaire get a score that is significantly below 36 points, meaning that the effect of fatigue on their daily routine is minor if it’s even noticeable. Arguments have been made that the threshold for indicating severe fatigue should be higher (roughly around 45 points), but no real changes have been made thus far.

Since its creation, the FSS has become one of the primary diagnostic and research tools for dealing with fatigue and multiple sclerosis, to the point where 50 percent or more studies on that topic have featured this scale. Its use is often linked to fatigue that occurs as a result of various disabilities, such as chronic illnesses. While it’s not as widespread as the Epworth Sleepiness Scale or the Multiple Sleep Latency Test, it has received praise for being a simple and reliable way to keep track of fatigue. Because the results are often internally consistent, this scale can be used to track progress while a patient is undergoing therapy. Over time, if the therapy is successful, it will start to show a significant reduction in daily fatigue impairment.


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