Factor Analysis of Epworth Sleepiness Scale Questions in a Sleep Population Across Disease States

Richard K. Bogan, MD, FCCP

President and Medical Director
SleepMed of South Carolina
Chairman, Chief Medical Officer
SleepMed, Inc.
Medical Director
Associate Clinical Professor
University of South Carolina Medical School
Columbia, South Carolina

The Epworth Sleepiness Scale (ESS) is an important tool for quickly assessing sleepiness in patients with sleep disorders. It is also useful for monitoring treatment progress. The ESS describes 8 scenarios that patients are asked to rate using a scale of 0 (no chance of dozing off) to 3 (high chance), with a maximum score of 24. A score of 10 or higher is defined as excessive sleepiness and often warrants further attention. Excessive sleepiness is fairly common, with studies reporting the prevalence occurring 3 or more days per week at between 4% and 20% of the population; severe excessive sleepiness has been reported at 5% of the population.1 The magnitude and distribution of sleepiness across multiple sleep disorders as measured with the ESS warrants further study, and may yield potentially important benefits for patient assessment. Analyzing records from about 10,000 patients (male, 52%), the degree of sleepiness was assessed and populations within select disease domains—eg, OSA, idiopathic hypersomnia, central hypersomnolence insomnia—were analyzed. Patterns were apparent in ESS responses: no patients who scored as being non-sleepy had difficulty staying awake while stopped at a traffic light, whereas patients who were found to be very sleepy generally did. Patients who self-rated sleepy on the ESS (≥10) also tended to rate specific scenarios higher: as a passenger in a car for an hour, sitting quietly after lunch, and sitting and talking to someone. However, no differentiation across the various disease domains was identified in this large survey. Clinicians who assess patients with sleep disorders need to be able to gauge how sleepy they are, in the same way that blood pressure measurements are used to ascertain the degree of hypertension. The study further characterizes the ESS as a fast assessment tool that is reliable across multiple sleep disorders.

References

Ohayon MM From wakefulness to excessive sleepiness: what we know and still need to know. Sleep Med Rev 2008;12(2):129-41.

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