The assessment of daytime sleep propensity: a comparison between the Epworth Sleepiness Scale and a newly developed Resistance to Sleepiness Scale.
BACKGROUND
The Epworth sleepiness scale (ESS) is widely used as a way of measuring subjective sleep propensity in research and clinical practice. Psychometric studies do not rule out the presence of more than one latent dimension underlying the items.


OBJECTIVE
Aims of the present study were to: (a) evaluate psychometric proprieties of the ESS by means of classic psychometric techniques; (b) compare them with those from a newly developed resistance to sleepiness scale (RSS); (c) evaluate, following the latent trait theory, whether the items of both ESS and RSS could be conceptualized as different levels of an interval variable representative of a single latent trait related to sleep propensity.


METHODS
One hundred and forty-six inpatients suffering from different sleep disorders filled in both the RSS and ESS in a sleep disorder centre.


RESULTS
Indexes of fit derived by the application of the extended logistic model are consistent with the idea that each ESS item can be conceptualized as different levels of an interval variable representative of a single latent trait. However, most of the ESS items are found to be located at the opposite extremes of this continuum.


CONCLUSIONS
The under representation of situations characterized by an intermediate soporific nature in the ESS could limit ESS sensitivity to detect intermediate variations of sleep propensity.
Violani
C
C
Department of Psychology, University of Rome La Sapienza, Via dei Marsi, 78-00185, Rome, Italy. cristiano.violani@uniroma1.it
Lucidi
F
F
Robusto
E
E
Devoto
A
A
Zucconi
M
M
Ferini Strambi
L
L
D000293:Adolescent; D000328:Adult; D000368:Aged; D001143:Arousal; D016009:Chi-Square Distribution; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography / Q000379:methods; D011187:Posture; D011594:Psychometrics / Q000379:methods; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology*; D012893:Sleep Wake Disorders / Q000145:classification / Q000175:diagnosis* / Q000523:psychology; D011795:Surveys and Questionnaires; D014851:Wakefulness / Q000502:physiology*