Chest
Volume 103, Issue 1, January 1993, Pages 30-36
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Clinical Investigations
Daytime Sleepiness, Snoring, and Obstructive Sleep Apnea: The Epworth Sleepiness Scale

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The Epworth Sleepiness Scale (ESS) is a simple questionnaire measuring the general level of daytime sleepiness, called here the average sleep propensity. This is a measure of the probability of falling asleep in a variety of situations. The conceptual basis of the ESS involves a four-process model of sleep and wakefulness. The sleep propensity at any particular time is a function of the ratio of the total sleep drive to the total wake drive with which it competes. ESS scores significantly distinguished patients with primary snoring from those with obstructive sleep apnea syndrome (OSAS), and ESS scores increased with the severity of OSAS. Multiple regression analysis showed that ESS scores were more closely related to the frequency of apneas than to the degree of hypoxemia in OSAS. ESS scores give a useful measure of average sleep propensity, comparable to the results of all-day tests such as the multiple sleep latency test.

Section snippets

SLEEPINESS RECONSIDERED

The word sleepiness did not appear in the index of medical text books in the past. It is a concept that is still not widely used or clearly understood. There is confusion about what different people consider sleepiness to be and this has led some to use a circular argument to define sleepiness as that which is measured by one or other tests of sleepiness.

Some consider sleepiness to be a state involving feelings of tiredness or fatigue and the subjective changes that immediately precede sleep

A FOUR-PROCESS MODEL OF SLEEP AND WAKEFULNESS

A model of sleep and wakefulness must involve at least four processes for it to explain sleepiness. The details and ramifications of such a theory are beyond the scope of this report and will be described elsewhere. However, the essence of this model is that two sleep processes contribute to the total sleep drive and two wake processes contribute to the total wake drive. What I call the primary sleep drive is due to an intrinsic CNS process that varies with a circadian rhythm having a peak at

RATIONALE OF THE ESS

The ESS is a simple questionnaire that asks the subject to rate on a scale of 0 to 3 the chances that, as part of his “usual way of life in recent times,” he would doze in each of eight different situations.4 The situations were chosen on a priori grounds to vary in their soporific nature from highly soporifi c (“lying down to rest in the afternoon when circumstances permit”) to much less soporific (“sitting and talking to someone”).5 The ESS score is the sum of eight item scores and can range

METHODS

All subjects were fee-paying patients, investigated in the Sleep Disorders Unit at Epworth Hospital, a private hospital in Melbourne, Australia. They answered the ESS without assistance at the end of their first interview. They had one night's diagnostic polysomnography with sleep staging by EEG (electrode positions C4-A1), left and right EOG, submental EMG, measurements of nasal and oral airflow, thoracic and abdominal respiratory movements, arterial oxygen saturation measured by a pulse

Analysis of Variance

The results for primary snorers and the three categories of OSAS are summarized in Table 1. There were many more patients with primary snoring or “mild” OSAS than there were with “moderate” or “severe” OSAS. Between these groups there were significant overall differences in the patients' ages, BMI, RDI, minimum SaO2, and ESS scores. However, posthoc Scheffé tests did not reveal significant differences in age between any paired groups. The BMI was significantly lower for primary snorers than for

DISCUSSION

The results provide further evidence that ESS scores give valid measurements of ASP or daytime sleepiness as defined herein. The scores increased linearly with the severity of OSAS and distinguished primary snorers from patients with OSAS, even of mild degree. In the patients with OSAS, it was the frequency of apneas and hypopneas that bore the closest relationship to their ASP as measured by ESS scores. The degree of hypoxemia, measured by the minimum SaO2 overnight, was significantly

REFERENCES (33)

  • TH Monk

    Subjective ratings of sleepiness–the underlying circadian mechanisms

    Sleep

    (1987)
  • Y Cook et al.

    The effects of nocturnal sleep, sleep disordered breathing and periodic movements of sleep on the objective and subjective assessment of daytime somnolence in healthy aged subjects

    Sleep Res

    (1988)
  • LC Johnson et al.

    Daytime sleepiness, performance, mood, nocturnal sleep: the effect of benzodiazepine and caffeine on their relationship

    Sleep

    (1990)
  • AW MacLean et al.

    The Stanford Sleepiness Scale in a clinic sample: the need for revision

    Sleep Res

    (1990)
  • MS Aldrich

    Cardinal manifestations of sleep disorders:

  • T Roth et al.

    Daytime sleepiness and alertness

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    Manuscript received February 5; revision accepted June 2.

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