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Sleepiness Level and Degree: Research Instruments Research Paper

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Updated: Mar 21st, 2022


Sleep can be defined as a lowered ability of reaction to stimuli though can be easily reversed than a coma or hibernation in some animals. Characteristically, almost all muscles that are involuntary become inactive during sleep. Sleep can be easily defined as a recurring state of lacking consciousness with suspension of the sensory abilities.

Sleep disorders on the other hand or somnipathy refers to a disorder of patterns of sleeping in a person or even animals. Various symptoms of sleep disorders do exist. One of the most common is daytime sleepiness. This is mostly characterized by sleepiness which is persistent, and a feeling of low or lacking energy. There are various ways of measuring the level and degree of daytime sleepiness. Although the objective measure, MSLT (Multiple Sleep Latency Test) bears a gold standard consideration, there exists other ways like the Epworth Sleepiness Scale and the Stanford Sleepiness Scale which are inexpensive and require less time to conduct (Takegami, 2009).

Epworth Sleepiness Scale (E.S.S)

ESS is defined as a questionnaire that can be self-administered with only 8 questions. It provides that persons average propensity of sleep during daytime. This method was first introduced by Dr John Murray in Australia while at the Hospital of Epworth in Melbourne. The method or standard has gained popularity and is now used worldwide for making sleepiness assessments.

Workings of the Epworth Sleepiness Scale

This simple method uses questionnaires which have a scale of between 0 and 3. The questionnaires are meant to find out the probability of sleeping in eight different scenarios engaged by most people even if not every day. Since dozing off depends on the number of times a person happens to be in a position that would cause them to doze off, individuals are not asked how often in particular situations do they doze off. The mental judgment required is easily made meaningfully by most people. A sum ranging from 0 to 24 of the score on the eight items makes the total score of the ESS. Even without assistance these answers are known to be easily provided within 3 minutes. A score of 10 or more may indicate excessive sleepiness and a further doctor’s evaluation may be necessary.

Validity and reliability of the Epworth Sleepiness Scale

Despite the fact that the Multiple Sleep Latency Test is considered a gold standard on which other sleepiness measurements ought to be compared, the ESS can be said to be quite valid and reliable. The fact that more than one sleep propensity situation is measured by ESS gives it a more validity edge. This is from the fact that a persons sleep propensity in a situation might differ given another situation.

Patients experiencing sleep disorders of various kinds are known to have had ESS scores that have significantly correlated with the mean latency of sleep measured by MSLT (Murray, 1991). Patients of sleep disorders have also been distinguished significantly from the test subjects using the ESS. Murray (1991) further assured the reliability of the ESS using two scenarios with different subjects. The first being 104 medical students in their third year of study at the Medical School of Monash University in Melbourne. The students had mean sleep duration of 7.7 hours on week nights and 8.4 during weekends. The second group of subject was 54 patients who were experiencing Obstructive Sleep Apnea Symptoms.

The healthy medical students were instructed to take an ESS in early May 1991.Without warning, the same students were again required to answer the ESS questionnaire 5 months past the first test. It should also be noted that at the time of undertaking the second ESS, they had just come back from a 2 months winter vacation. The mean ESS score for the first instance was 7.4 and a standard deviation (SD) of 3.9 while on the second test it was 7.6 with a standard deviation of 73.8. These two scores produced a mean difference of 0.20 and a standard deviation (SD) of 2.3 which is statistically not significant (Murray, 1991).

On contrary terms, the 54 patients with sleeping disorders had an initial ESS mean score 14.3 and SD 3.6. The range of the score was 5 – 21. On treatment with Continuous Positive Airway Pressure (CPAP), the mean ESS score came down to 7.4 and SD of 4.1. The range of ESS score also reduced to 0 – 16. In the final run, the difference between the two tests was 7.0 with SD of 5.2 which obviously is statistically significant (Murray, 1991).

Therefore, although there is always the possibility of a person giving false information so as to attain the desired ESS score especially in legal matters(Nakayama, 1998), the two subjects that were under the study ended up producing the most logical results. This method can thus be said to have shown reliability in test-retest. It is thus a valid and reliable method for finding out patients who might be having sleep disorders.

Stanford sleepiness scale

Stanford Sleepiness Scale (SSS) is yet another method that quickly measures the alert level of a person. An alert level of 1 would be most ideal. This method that measures the level of alertness at different time periods during the day would portray a serious debt in sleep if a person were to go below 3 when they ought to be alert. The SSS has a scale of between 1 and 7 with x representing asleep. Therefore at different time periods, a person would answer the questionnaires by providing the appropriate scale alongside 8 of the questionnaires (Glenville, 1978).

Validity and reliability of the Stanford Sleepiness Scale

In an experiment by Simon S. Smith to access Accidents and find their possible solutions, 32 novice drivers with a mean age of 19.88 years having a mean of 1.65 years of experience driving were used. Using the SSS scale, they rated their alert levels whereby 1 referred to being active, wide awake or alert. 7 referred to a point of onset of sleep. The test were carried twice once during daytime and another test at 3.a.m. in the night.

The results showed that at night, there was a significant feeling of sleepiness. This feeling attained a mean score of 4.32 with SD of 0.99. During the day however, the SSS score only stood at a mean of 2.22 with a SD of 1.16 (Takegami, 2009). These two results can produce a statistical significance when their mean difference is computed.


It can therefore be concluded that the Stanford Sleepiness Scale produces results that reflect the expected outcomes (Maclean 1992). It can thus be said to be reliable. This method can be validly used to measure the alert level in a person at different times of the day.


Glenville M, et al. (1978). Broughton R. Reliability of the Stanford Sleepiness Scale compared to short duration performance tests and the Wilkinson Auditory VigilanceTask. Oxford:PubMed.

Maclean, a. et al. (1992). Psychometric evaluation of the Stanford Sleepiness Scale. Journal of Sleep Research. 1(1), 35-39

Murray,J. et al. (1991). A new method for measuring daytime sleepiness: the Epworth sleepiness scale. Sleep 14(6), 540-545

Nakayama, T. et al (1998). Validity, Reliability and Acceptability of the Japanese Version of the General Well-Being Schedule (GWBS). Great Britain:Kluwer.

Takegami, M. et al. (2009). Development of a Japanese version of the Epworth Sleepiness Scale (JESS) based on item response theory. Sleep medicine. 10(5), 556-565

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