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Assessing subjective daytime sleepiness: an internal state versus behavior approach
June J Pilcher1, Cynthia L S Pury, Eric R Muth
1Department of Psychology, Clemson University, USA.
Behavioral Medicine (Washington, D.C.)
|May 19, 2004
Summary
This study found that the Epworth Sleepiness Scale (ESS) measures a different aspect of subjective sleepiness than the Stanford Sleepiness Scale (SSS), Profile of Mood States (POMS), and Visual Analogue Scales (VAS). The ESS assesses behavior, while the others assess internal states.
Area of Science:
- Psychology
- Sleep Science
Background:
- Subjective sleepiness is a complex phenomenon.
- Existing measures may capture different dimensions of sleepiness.
Purpose of the Study:
- To apply Lang's theory of emotional response systems to subjective sleepiness.
- To differentiate the measurement properties of common sleepiness scales.
Main Methods:
- Correlational and factor analysis of four sleepiness measures.
- Participants (N=274) completed the Stanford Sleepiness Scale (SSS), Profile of Mood States (POMS), Visual Analogue Scales (VAS), and Epworth Sleepiness Scale (ESS).
Main Results:
- The SSS, POMS, and VAS measures showed higher intercorrelations than with the ESS.
- Factor analysis revealed that the ESS loaded on a separate factor from the SSS, POMS, and VAS.
- The ESS appears to measure a distinct component of sleepiness.
Conclusions:
- The ESS assesses a behavioral aspect of sleepiness.
- The SSS, POMS, and VAS measures capture an internal state related to sleepiness.
- Lang's theory provides a framework for understanding these differences in sleepiness measurement.