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

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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.

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Authors and Affiliations

  1. Escola de Psicologia e Ciências da Vida, Universidade Lusófona de Humanidades e Tecnologias and COPELABS, Campo Grande, 376, 1749-024, Lisboa, Portugal

    Paulo Sargento, Paulo Lopes & Jorge Oliveira

  2. Universidad de Salamanca, Salamanca, Spain

    Victoria Perea & Valentina Ladera

Authors
  1. Paulo Sargento
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  2. Victoria Perea
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  3. Valentina Ladera
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  4. Paulo Lopes
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  5. Jorge Oliveira
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Correspondence to Paulo Sargento.

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Sargento, P., Perea, V., Ladera, V. et al. The Epworth Sleepiness Scale in Portuguese adults: from classical measurement theory to Rasch model analysis. Sleep Breath 19, 693–701 (2015). https://doi.org/10.1007/s11325-014-1078-6

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  • DOI: https://doi.org/10.1007/s11325-014-1078-6

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