Sleepiness scales

EDS, of any cause, is common. The exact prevalence is difficult to determine, since sleepiness is not an all-or-none phenomenon, but it can be estimated. Using a subjective scale, the Epworth Sleepiness Scale (ESS), about 26% of normal subjects score >10 and about 2.5% score >15 (1). Using an objective method, the MSLT, about 32% of subjects score in the severely sleepy range (2). In addi-... 

Questionnaires and rating scales for sleepiness can be divided into two broad categories those that estimate short-term, or moment-to-moment fluctuations, and those that assess more long-term (steady-state, permanent) states. The former is typified by the Stanford Sleepiness Scale (SSS), and is best suited for evaluation of sleepiness/alertness throughout the circadian cycle. The latter are typified by the ESS, and are best suited for the evaluation of sleep disorders. 

The Stanford Sleepiness Scale (SSS) (5) was the most commonly used scale for sleepiness prior to the ESS. It seems to reliably quantify sleepiness in healthy persons (5,6), but its usefulness in sleep disorders is less certain. The SSS consists of seven descriptive phrases that describe the subject s state (see Fig. 1), of which subjects must choose the one that best describes how they feel at the time. Thus,... 

The Karolinska Sleepiness Scale (8) is comparable to the SSS. The choice here is among nine descriptive statements (phrases that describe the subject s state). Here the statements specifically refer to how the patient felt in the previous 10 min. 

Because of its conciseness, the ESS easily fits on a single 8x11 sheet of paper, and takes less than 3 min for patients or families to complete. Its items are short, simple, easily understandable even by poorly educated patients, and it yields a simple number (from 0 to 24). Unlike the SSS, which refers to a state at a particular time of the day or night, the ESS refers to a general state, and is more suited to evaluate disease versus health. For those reasons, it is currently and by far the most used sleepiness scale, both in clinical practice and in research. 

Figure 2 The Epworth Sleepiness Scale. Each question is answered with a number from 0 (not at all likely to fall asleep) to 3 (very likely to fall asleep). This yields a total of 0 (minimum) to 24 (maximum), and scores above 10 are thought to warrant investigation.

It is important for clinicians and researchers alike to know whether they should rely on objective or subjective measures of sleepiness, or both, and how the two types of measures relate to each other. Since sleep latency on the MSLT is considered the gold standard for objective measure and grading of sleepiness, studies have used this as the objective gold standard. However, not all subjective scales have been studied. Several investigators have reported weak or no association between sleep latency and subjective scales such as the Stanford Sleepiness Scale (26-29). The SWAI, or more specifically its EDS subscale, appears to reli-... 

Herscovitch J, Broughton R. Sensitivity of the Stanford Sleepiness Scale to the effects of cumulative partial sleep deprivation and recovery over sleeping. Sleep 1981 4 83-92. 

Johns MW. A new method of measuring sleepiness the Epworth Sleepiness Scale. Sleep 1991 14 540-545. 

Hardinge FM, Pitson DJ, Stradling JR. Use of Epworth Sleepiness Scale to demonstrate response to treatment with nasal continuous airway pressure in patients with obstructive sleep apnoea. RespirMed 1995 89 617-620. 

Johns MW. Sleepiness in different situations measured by the Epworth Sleepiness Scale. Sleep 1994 17 703-710. 

Benbadis SR, Mascha E, Perry MC, Wolgamuth BR, Smolley LA, Dinner DS.. Association between Epworth Sleepiness Scale and MSLT in a clinical population. Ann Intern Med 1999 130 289-292. 

Chervin R, Aldrich MS, Pickett R, Guilleminault C. Comparison of the results of Epworth Sleepiness Scale and multiple sleep latency test. J Psychosom Res 1997 42 145-155. 

Smolley LA, Ivey C, Farkas M, Faucette E, Murphy S. Epworth Sleepiness Scale is useful for monitoring daytime sleepiness. Sleep Res 1993 22 389. 

Sander AM, Mohan KK, Axelrod BN, Nahhas A, Kapen S. The Epworth Sleepiness Scale an unworthy adversary to clinical interview. Sleep Res 1996 25 355... 

Sangal RB, Mitler MM, Sangal JM. Subjective sleepiness ratings (Epworth Sleepiness Scale) do not reflect the same parameter of sleepiness as objective sleepiness (maintenance of wakefulness test) in patients with narcolepsy. Clin Neurophysiol 1999 110 2131-2135. 

Figure 7 PVT reaction times prior to the first uncontrolled sleep attack during total sleep deprivation. Fourteen subjects completed 42 hr of total sleep deprivation and completed a 20-min PVT every 2 hr (represented by the closed circles) 19 subjects completed 88 hr of total sleep deprivation and completed a 10-min PVT every 2 hr (represented by the open circles). The number of test bouts (up to 30) prior to an uncontrolled sleep attack (failure to respond for 30 sec on the PVT) is represented on the bottom abscissa, with time prior to the sleep attack (up to 6 min) represented on the top abscissa. In both subject groups a progressive decline in performance on the visual PVT was evident within minutes of an uncontrolled sleep attack on console. This study also demonstrated an increase in subjective sleepiness (measured using the Stanford Sleepiness Scale) in the test bouts prior to the one in which the first sleep attack occurred. Taken together, these findings suggest that even a very sleepy subject cannot fall asleep while performing computerized tasks without some levels of awareness. (From Ref. 95.)...

Perhaps the most common type of verbal report used in sleep deprivation studies is a measure of subjective sleepiness. Subjective sleepiness is generally assessed by self-report scales (see also Chap. 1), such as the Stanford Sleepiness Scale (19), the Epworth Sleepiness Scale (20), visual analog scales (21), and the vigor and fatigue subscales on the Profile of Mood States (POMS Educational and Industrial Testing Service, San Diego, CA). These measures have been used in studies on the effects of sleep deprivation (22-25), shift work (26-28), and sleep disorders (29,30). 

Johnson S. How sleepy are practicing physicians A field trial of the Epworth Sleepiness Scale. Sleep Res 1997 26 671. 

Glenville M, Broughton R. Reliability of the Stanford Sleepiness Scale compared to short duration performance tests and the Wilkinson Auditory Vigilance task. In Passouant P, Oswald I, eds. Pharmacology of the States of Alertness. Oxford Pergamon, 1979 235-244. 

One could reasonably believe that complaining of chronic daytime somnolence is a major risk for traffic accidents. Surprisingly, studies on patients suffering from chronic daytime somnolence (9,10) failed to find a link between the risk of traffic accidents and sleepiness measured on a behavioral scale (i.e., Epworth Sleepiness Scale). This could be explained by the fact that subjective questionnaires do not correlate with objective measures of daytime vigilance (11). Another possible explanation could be that sleepiness is dangerous only when perceived during at risk activities. 

Subjective (e.g., Epworth Sleepiness Scale) and objective [e.g., Multiple Sleep Latency Test (MSLT)] daytime somnolence quantification does not seem to provide valuable information on patients risks. This could be explained by the fact that sleep-related accidents occur at certain times when behavioral and chronobiological factors play an important role. Medical and legal issues could nevertheless require an objective test, such as the Maintenance of Wakefulness Test (MWT), to confirm that treated apneic patients present a normal level of vigilance. 

Chervin RD, Aldrich MS. The Epworth Sleepiness Scale may not reflect objective measures of sleepiness or sleep apnea. Neurology 1999 52 125-131. 

Kamimori et al. (129) tested the effects of approximately 150, 300, and 600 mg caffeine on noradrenaline and adrenaline levels, sleep latency, Stanford Sleepiness Scale ratings, and choice reaction time in volunteers who were dosed after 49 hr of continuous wakefulness (and kept awake for an additional 12 hr). 

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