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Sleep and Breathing

, Volume 19, Issue 2, pp 693–701 | Cite as

The Epworth Sleepiness Scale in Portuguese adults: from classical measurement theory to Rasch model analysis

  • Paulo SargentoEmail author
  • Victoria Perea
  • Valentina Ladera
  • Paulo Lopes
  • Jorge Oliveira
Original Article

Abstract

Background

The Epworth Sleepiness Scale (ESS) is a largely wide used scale for sleepiness assessment. Measurement properties are studied in a sample of Portuguese adults, using different statistical procedures.

Methods

The sample consisted of 222 Portuguese adults (97 men and 125 women) with a mean age of 42 years old (SD = 12.5), 46 of which had obstructive sleep apnea (OSA) confirmed by polysomnography. The participants were assessed with the ESS, which was tested through a quantitative analysis based on the classical measurement theory (CMT) or the Rasch model (RM) conventions.

Results

A principal component factor analysis was performed according to the CMT, revealing a single factor explaining 39.92 % of the total variance of the scale. Internal consistency measured by Cronbach’s α coefficient was of .77. The mean of inter-item correlation was of .31 (.05 < r > .47), whereas the item-total correlations were considered good (.46 < r > .73). The ESS total score for OSA patients was significantly higher than healthy participants (p < .05). Overall data from the RM analysis was consistent with the guidelines of Linacre and essential unidimensionality was empirically corroborated (61 % the percentage of variance explained by the Rasch analysis). Model fit is adequate and the reliability coefficients for both items (.99) and subjects (.78) were considered good. The Cronbach’s α coefficient was also satisfactory (.78).

Conclusions

The ESS showed an adequate structural, internal, and criterion validity, both in the CMT and the RM, suggesting this as a useful and effective measure for assessing sleepiness in Portuguese adults.

Keywords

Epworth Sleepiness Scale Classical measurement theory Rasch rating scale model Obstructive sleep apnea 

Notes

Conflict of interest

None, for all authors.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Paulo Sargento
    • 1
    Email author
  • Victoria Perea
    • 2
  • Valentina Ladera
    • 2
  • Paulo Lopes
    • 1
  • Jorge Oliveira
    • 1
  1. 1.Escola de Psicologia e Ciências da VidaUniversidade Lusófona de Humanidades e Tecnologias and COPELABSLisboaPortugal
  2. 2.Universidad de SalamancaSalamancaSpain

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