The Epworth Sleepiness Scale

The primary purpose of the ESS is to measure average sleep propensity (known elsewhere as excessive daytime sleepiness) through the application of a simple and accessible questionnaire.

Written by:

Tanya Hodgson

, Sleep Researcher
Last Updated: Thu, October 3, 2019
Fact checked by:

Marko Jevtic

, Sleep Specialist

One of the best methods for diagnosing and identifying sleeping disorders is polysomnography. It’s a procedure that takes place over an entire night at a sleep lab, where doctors and specialists monitor a variety of processes in your body while you sleep – brain activity, breathing patterns, muscle movement, eye movement, etc. However, this procedure is often quite expensive for some people, and the amount of time it takes can get in the way of their work schedules or other obligations.

Because of that, the first diagnosis options often include more accessible stuff. One of the most popular approaches to quickly identifying the presence of a sleep disorder is through various questionnaire-style tools. The advantage of these tools is that they often don’t require any formal training, and you can theoretically find them online and answer them before bringing the results to the doctor. Many of these questionnaires and scales have been translated into multiple languages for added accessibility.

However, criticisms have been made over the years about the subjective nature of potential answers. According to critics, it’s far too easy to misremember something or answer in a biased way, making the tests inaccurate. In this article, we will be looking into how this subjective nature manifests using one of the most popular diagnostic tools for sleep disorders out there – the Epworth Sleepiness Scale – as an example. Let’s get into it.

How Does the Epworth Sleepiness Scale Work?

The Epworth Sleepiness Scale (or ESS for short) was developed for adults by Dr. Murray Johns in 1990. It was named after the Epworth hospital in Melbourne, where he had previously (in 1988) established a sleep center. The modified version from 1997 is the one that sees professional use today and requires a license to be used. The primary purpose of the ESS is to measure average sleep propensity (ASP, known elsewhere as excessive daytime sleepiness) through the application of a simple and accessible questionnaire.

The questionnaire consists of 8 questions that the patient must answer and rate on a scale of 0-3 (meaning there are four different responses to each question). A rating of 0 means the patient would never doze off in that scenario. A score of 1 indicates a slight chance of dozing, while 2 and 3 correspond to “moderate” and “high” chance of falling asleep. This rating determines how likely the patient is to fall asleep or doze off in various situations. Here’s the full list, as it’s important to be aware of one crucial factor:

–          Sitting and enjoying a good book

–          Sitting, idle, in a public place (such as a park)

–          Watching television

–          Lying down to get some rest in the afternoon

–          Sitting and holding a conversation with someone

–          Sitting, inactive, after having lunch (without any alcohol involved)

–          Being a passenger in a vehicle for an hour with no breaks

–          In a car, stuck in traffic for around 5 minutes

If you look at official information about the ESS, you may come across the word “somnificity.” This term was also introduced by Dr. Johns, somewhere around 2002. Somnificity is a measure of how much a specific activity or posture contributes towards you falling asleep, or how much it hinders the prospect of sleeping for a majority of people. The ESS questions introduce scenarios with different levels of somnificity to provide a varied selection of situations and help doctors get an insight into the patient’s sleep propensity and sleeping habits.

You may also notice that no timeframe is referenced by the questionnaire (as in, you’re not asked to specifically look at the last week, for example). Instead, it’s presented as remembering these situations “in recent times.” This was specifically arranged so the period (often referred to as the “recall period”) is adaptable to what the patient can remember, which helps increase response accuracy. The only situation in which this doesn’t apply, and a clearer timeframe would be introduced, is treatment progress monitoring. The doctor may want you to remember how likely you were to fall asleep since the treatment started so that they can compare it to results from before the treatment plan began. For example, CPAP treatment for obstructive sleep apnea is guaranteed to cause a drop in the patient’s ESS score, as that treatment consolidates the sleep architecture of the patient, preventing fragmented sleep (a huge potential cause of fatigue, here as a result of blocked airways)

How Are ESS Scores Interpreted?

As mentioned before, each of the eight questions has four potential answers (0-3). These numbers will either be written in a small box next to the question, or the option to tick one of four checkboxes will be present. Other times (though much less often), these answers can be provided electronically or via phone or personal interview. It is of utmost importance to answer every single question as honest as possible because, without those answers, the whole test becomes invalid. The main modification of the upgraded ESS version from 1997 is the added instruction that says just that. Additionally, it’s not allowed to explain each question in detail for the patient, as this can potentially cause bias in their answers. If the patient answers the questions using half-values (such as responding with 1.5 instead of 1), it is recommended not to interrupt their questionnaire, and just accept the result. However, if the end result includes a half-point, round it up to the next integer.

Originally, the average score range was considered to be anywhere between 2 and 10 points (established by Dr. Johns himself). However, after more data, the lower limit was pushed towards zero points and is the average score range you will encounter these days. A resulting score higher than 10 points indicates an increased average sleep propensity or excessive daytime sleepiness. Increased ASP is almost always caused by a sleeping disorder, and so this test can often be used as a preliminary, “filtering” method to determine which patients need to be looked into further. The higher the score goes, the more sleepy the person is during the day, and the more fatigue endangers their overall health and safety. Here’s a brief list that can give you a rough idea on how severe your sleeping problems (and subsequent EDS) are:

–          A score between 0 and 5 points indicates a lower level of normal daytime sleepiness. Naturally, this is the best score you can get.

–          A score between 6 and 10 points indicates a higher level of normal daytime sleepiness. There is still nothing to worry about with this score, as it is considered in the “safe” range and doesn’t point towards sleeping disorders.

–          A score of 11 or 12 is the breaking point at which doctors may conclude you have a potential sleeping disorder. While nowhere close to severe, this score indicates a small amount of excessive daytime sleepiness.

–          A score between 13 and 15 points reaches the “moderate” level of excessive daytime sleepiness. While the interpretation can often resemble that of light EDS (depending on your doctor), this is already a troublesome result. There is no doubt that a person with this many points has a sleeping disorder.

–          A score between 16 and 24 points is considered a clear indicator of severe EDS. This level of fatigue is incredibly dangerous for the patient, and a more thorough diagnosis plan should begin as soon as possible. Methods include a Multiple Sleep Latency Test (or MSLT for short), polysomnography, etc.

Oddly enough, gender and age contribute almost nothing as factors towards the overall score. However, ethnicity does affect things – African-Americans have a noticeably higher average ESS score than most Caucasian Americans. Other significant contributors include depression or sleep-disordered breathing, which can alter the result to some degree. A large number of score reports collected from the general population so far indicate an above-average ASP. It corresponds to the fact that depending on individual demographics, a percentage ranging between 10% and 40% suffer from excessive daytime sleepiness in the United States. Almost every single person with narcolepsy gets a score that indicates moderate or severe EDS.

Criticisms and Downsides to the Epworth Sleepiness Scale

The biggest concern that plagues many critics of the ESS is its inherent subjectivity. Much like the Pittsburgh Sleep Quality Index (PSQI for short) or Stanford Sleepiness Scale (SSS), the Epworth sleepiness scale is susceptible to various forms of bias or inaccuracy. There are no guarantees that the patient will remember all their sleeping habits and patterns well enough to provide a good answer. As a result, the ESS is not meant to be used as the only diagnostic method in scenarios where the person’s ASP may cause legal problems or similar obstacles – in these cases, seek out additional tools, to get more substantial info. It is also unsuitable for diagnosing patients with cognitive impairments that are unable to provide precise answers as a result of their condition.

A common consequence of excessive daytime sleepiness is drowsy driving, one of the riskiest yet routinely performed activities, especially for working adults. The problem here is that the ESS can’t predict the exact amount of fatigue the person feels or how much it hinders their road performance – at least until the scores start hitting values of 15 or higher. At that point, it can be argued that the level of EDS is definitely a massive problem for any potential drivers.

Additionally, the ESS is not precise enough to detect which specific sleeping disorder the patient is dealing with. An increased average sleep propensity is a symptom of basically every sleeping disorder, making it hard to determine a single condition. Instead, the ESS is a good “first” test, a way to disqualify people without dangerous levels of excessive daytime sleepiness, since their likelihood of having a sleep disorder is very small. On top of that, it doesn’t specify what the major contributing factors may be for that potential sleeping disorder, making it less-than-ideal as a standalone diagnostic tool. Always ask for further examination if your score is 11 or higher, in case the doctor doesn’t mention it.

Note: If you’re unsure about any part of the ESS questionnaire, don’t write down your answers at home. Consult your doctor so they can know what’s happening early on, and ask them to supervise your answering process. Also, if you’re worried that you may have a sleeping disorder, don’t hesitate to open and maintain a sleep journal. Sleep tracking is one of the most helpful methods of contributing to a proper diagnosis.

Translations and Reception of the Epworth Sleepiness Scale

The original language used for the development and application of the ESS was English, as it was created in Australia. However, its incredible ease of use and accessibility even without formal training (you basically know enough about the procedure now to answer all of those questions yourself even before a doctor’s appointment) have led to its authorized translation into many different languages. It is very important to keep the translation as close as humanly possible in meaning to the original. The questions are all very deliberately worded to produce the most accurate answers, and dodgy translation, even if it’s tiny inaccuracies, can invalidate the whole procedure. Copyright protects the ESS from any changes, although special circumstances can justify it – with written permission, of course.

Overall, the ease with which a doctor or researcher can conduct ESS testing (for an individual patient or subject, or an entire group of people) has led to its widespread use in clinics all around the globe. It’s considered one of the most reliable subjective sleepiness scales, especially for keeping track of patient progress as a result of regular treatment.


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Tanya is a professional writer and editor with a B.A. in English from the University of Chicago. Tanya has been fighting insomnia for most of her adult life, and she knows firsthand how vital a good night’s rest can be for people with sleep problems.

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