The Epworth Sleepiness Scale The Epworth Sleepiness Scale is widely used in the field of sleep medicine as a subjective measure of a patient's sleepiness. The test is a list of eight situations in which a patient rates his/her tendency to doze on a scale of 0, no chance of dozing, to 3, high chance of dozing. The total score is based on a scale of 0 to 24. How Sleepy Are You? How likely are you to doze off or fall asleep in the following situations? You should rate your chances of dozing off, not just feeling tired. Even if you have not done some of these things recently try to determine how they would have affected you. For each situation, decide whether or not you would have: · No chance of dozing =0 · Slight chance of dozing =1 · Moderate chance of dozing =2 · High chance of dozing =3 Write down the number corresponding to your choice in the right hand column. Total your score below. Situation Chance of Dozing Sitting and reading · Watching TV · Sitting inactive in a public place (e.g., a theater or · a meeting) As a passenger in a car for an hour without a · break Lying down to rest in the afternoon when · circumstances permit Sitting and talking to someone · Sitting quietly after a lunch without alcohol · In a car, while stopped for a few minutes in traffic · Total Score = ________________________ Reference: Johns MW. A new method for measuring daytime sleepiness: The Epworth Sleepiness Scale. Sleep 1991; 14(6):540-5. Sleep. 17(8):703-710 © 1994 American Sleep Disorders Association and Sleep Research Society Sleepiness in Different Situations Measured by the Epworth Sleepiness Scale Murray W. Johns Sleep Disorders Unit. Epworth Hospital, Melbourne, Victoria, Australia Summary: This investigation examines how the sleep propensity (SP) in one test situation, such as the Multiple Sleep Latency Test (MSLT), is related to sleepiness in daily life, as assessed by the Epworth Sleepiness Scale (ESS). This is a self-administered questionnaire, the item scores from which provide a new method for measuring SPs in eight different real-life situations. The ESS item scores were analyzed separately in four groups of subjects: ISO adult patients with a variety of sleep disorders, 87 medical students who answered the ESS on two occasions 5 months apart, 44 patients who also had MSL Ts and 50 patients whose spouses also answered the ESS about their partner's sleepiness. The ESS item scores were shown to be reliable (mean rho = 0.56, p < 0.001). The SP measured by the MSLT was related to three of the eight item scores in a multiple regression (r = 0.64, p < 0.001). The results ofnon parametric ANO VA, Spearman correlations, Wilcoxon's t tests, item and factor anal ysis suggest that indi vid ual measurements ofSP involve three components of variation in addition to short-term changes over periods of hours or days: a general characteristic of the subject (his average SP), a general characteristic of the situation in which SP is measured (its soporific nature) and a third component that is specific for both subject and situation. The SP in one test situation, including the MSL T, may not be a reliable indicator of a subject's average SP in daily life. Perhaps we should reexamine the current concept of daytime sleepiness and its measurement. Key Words: Sleep propensity­ Daytime sleepiness-Epworth Sleepiness Scale. Excessive daytime sleepiness is an important symp­ general characteristic of each subject. To what extent tom of several chronic sleep disorders, including ob­ this is true is seldom questioned and has not been structive sleep apnea (OSA), narcolepsy, idiopathic hy­ adequately tested. persomnia and periodic limb movement disorder. The Several variations of the MSLT have been proposed, Multiple Sleep Latency Test (MSLT) is widely accepted the best known of which is the Maintenance of Wake­ as the gold standard for measuring such sleepiness, a fulness Test (MWT) (5). The MSLT is a more widely position recently reinforced by the American Sleep used and tested method than the MWT, but both have Disorders Association (l,2). The word sleepiness is undergone tests of validity (2,5-8). Both are based on used here in the sense of sleep propensity (SP), not of the reasonable premise that the quicker a subject falls tiredness or other subjective feelings as measured by asleep in the test situation the higher his level of sleep­ the Stanford Sleepiness Scale or a visual analog scale iness. Sangal et al. compared the results ofMSLTs and of alertness-sleepiness, which are not significantly re­ MWTs done on the same day in 258 patients with a lated to SP (3,4). variety of sleep disorders (9). They found a correlation It is generally assumed that if subjects are sleepy in of 0.41 between the mean SLs measured in these two the MSLT [i.e. they have a mean sleep latency (SL) ostensibly valid tests of SP. This was statistically sig­ < 10 minutes, particularly if <5 minutes], they will nificant (p < 0.001), but accounted for less than 17% also be sleepy in other "low-stimulus" situations. Con­ of the variance. Overall, about one-third of their pa­ versely, if subjects are not sleepy in the MSLT (SL > 10 tients in various diagnostic categories had discordant minutes), they will not be sleepy in daily life either. It results, being relatively sleepy on one test but not on is assumed that the SP measured by the MSL T is a the other. The authors concluded that the MSL Twas measuring sleepiness, but the MWT was measuring the "capacity for wakefulness". Because both tests mea­ Accepted for publication July 1994. sure the same variable, the latency before sleep onset, Address correspondence and reprint requests to Dr. Murray W. Johns, Sleep Disorders Unit, Epworth Hospital, Erin Street, Rich­ these results must raise doubts about the commonly mond, Victoria 3121, Australia. accepted unitary concept of sleepiness. 703 704 M. W. JOHNS The Epworth Sleepiness Scale (ESS) uses a quite dif­ of the eight situations in the ESS has been described ferent method for measuring SP based on the subject's previously for two groups of subjects, "sleepy" patients retrospective reports of dozing behavior in eight sit­ and medical students (16). The most soporific situa­ uations that are commonly met in daily life (10). ESS tions generally involve prolonged inactivity such as scores have been correlated significantly with the mean sitting or lying down with little body movement, little SL in MSLTs (10). Like the MSL T and the MWT, ESS interaction with other people, particularly by talking, scores can distinguish groups of patients with various and little environmental stimulation by way of thermal sleep disorders from normal subjects (10-12) and are discomfort, bright light, loud noise, etc. However, some correlated significantly with the severity of OSA mea­ subjects respond paradoxically and fall asleep in what sured by the frequency of apneas and hypopneas (Il­ seems like a high-stimulus situation, subjected to very lS) in some but not all investigations. The ESS has a loud noise and bright flashes oflight (19). Many sub­ high test-retest reliability and a high level of internal jects respond to their first night in the sleep laboratory, consistency among its eight items (16). with its novelty and attachment of wires, by having This report examines the relationship between SPs worse sleep than on subsequent nights in the laboratory measured in different situations. It is not intended to or at home. Yet some, paradoxically, sleep better on question the substantial body of evidence for the va­ their first night in the sleep laboratory than on later lidity of the MSLT or related tests as measures of SP nights or at home (20). Similarly, some subjects fall within their respective test situations. Rather, it is in­ asleep quicker (i.e. they have a higher SP) in the MWT tended to examine the question of how far the sleep­ when instructed to stay awake than in the MSLT when iness that such tests measure can be generalized to instructed to fall asleep (9). It should not surprise us, other situations and to daily life. To do this we must therefore, that despite overall similarities in the rela­ reexamine some current concepts and introduce some tive soporific nature of various situations we may also others. find differences between individual subjects or groups. For the purposes of this discussion, the sometimes The soporific nature of different situations substantial but short-term fluctuations in SP, such as and activities with the time of day, after taking a sedative drug or after a night's sleep deprivation, are ignored. The SP It is self-evident that people fall asleep more quickly that a subject usually shows in a particular situation and more often if they lie down rather than stand up. will be called his situational sleep propensity. The Simply changing posture modifies SP, presumably by MSLT measures one situational SP, the MWT another. changing the input to the ascending reticular activating So, too, would each of the eight item scores of the ESS. system from proprioceptors in the postural muscles These are less accurate than the measurements of SL and joints. When we purposely decide to sleep we ini­ in the MSLT and MWT, but cover a wider range of tiate a process that decreases input to the ascending situations that are, arguably, more relevant to daily reticular activating system in several ways and thereby life. The ESS score is one way of combining several increases SP, no matter at what time of day or night different situational SPs to provide a measure ofa more this occurs.