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The fairness of the Epworth Sleepiness Scale: two approaches to differential item functioning
Linköping University, Department of Clinical and Experimental Medicine, Clinical Neurophysiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Sinnescentrum, Department of Neurophysiology UHL.
Linköping University, Department of Medical and Health Sciences, Nursing Science. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Clinical Neurophysiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Sinnescentrum, Department of Neurophysiology UHL.
Linköping University, Department of Medical and Health Sciences, Nursing Science. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Cardiology UHL.ORCID iD: 0000-0001-7431-2873
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2013 (English)In: Sleep and Breathing, ISSN 1520-9512, E-ISSN 1522-1709, Vol. 17, no 1, 157-165 p.Article in journal (Refereed) Published
Abstract [en]

Purpose

Differential item functioning (DIF) is said to exist in an item if a subject’s response to the item is affected by other aspects than that which the test is intended to assess. DIF might affect the validity of a test. The aim of this study was thus to examine whether any of the items in the Epworth Sleepiness Scale (ESS) exhibits DIF regarding age or gender, and if so, to which degree.

Methods

Using previously collected cross-sectional ESS data from 1,168 subjects with different clinical characteristics (61% males, mean age 67.8 year (SD 12.2 year)), ordinal regression as well as Rasch-based DIF analyses were performed.

Results

Concerning age, both DIF analyses showed DIF for age in items 3 (inactive in a public place), 4 (passenger in a car), and 8 (in a car that has stopped in traffic). The Rasch model also showed DIF for gender in item 3. The DIF magnitudes as judged by McFadden pseudo-R2 changes were, however, only minor.

Conclusions

ESS has small but reproducible DIF for age in items 3, 4, and 8. The detected DIF might be worth to consider in large-sample studies, although it probably has no effect on an individual basis.

Place, publisher, year, edition, pages
Springer, 2013. Vol. 17, no 1, 157-165 p.
Keyword [en]
Epworth Sleepiness Scale, Differential item functioning, Sleep, Daytime sleepiness
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-89964DOI: 10.1007/s11325-012-0664-8ISI: 000315167200029PubMedID: 22367404OAI: oai:DiVA.org:liu-89964DiVA: diva2:610599
Available from: 2013-03-12 Created: 2013-03-12 Last updated: 2017-12-06
In thesis
1. Psychometric aspects of obstructive sleep apnea syndrome
Open this publication in new window or tab >>Psychometric aspects of obstructive sleep apnea syndrome
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Introduction: Obstructive sleep apnea (OSA) is a common chronic disorder consisting of episodes with impaired breathing due to obstruction of the upper airways. Treatment with Continuous Positive Airway Pressure (CPAP) is a potentially effective treatment, but adherence is low. Several potential factors affecting adherence, e.g., subjective sleepiness and personality, are only quantifiable through questionnaires. Better knowledge about psychometric properties of such questionnaires might improve future research on CPAP adherence and thus lead to better treatment options.

Aim: Study I: To describe the devlopment and initial testing of the Side Effects of CPAP treatment Inventory (SECI) questionnaire. Study II: To describe the prevalence of Type D personality in OSAS patients with CPAP treatment longer than 6 months and the association with self-reported side effects and adherence. Study III: To study whether any of the items in the Epworth Sleepiness Scale (ESS) exhibit differential item functioning and, if so, to which degree. Study IV: To examine the evolution of CPAP side effects over time; and prospectively assess correlations between early CPAP side effects and treatment adherence.

Patients and Methods: In study I, SECI items were based on a literature review, an expert panel and interviews with patients. It was then mailed to 329 CPAP-treated OSAS patients. Based on this, a principal component analysis was performed, and SECI results were compared between adherent and non-adherent patients. In study II, the population consisted of 247 OSAS patients with ongoing CPAP treatment. The DS14 was used to assess the prevalence of type D personality, and SECI and adherence data from medical records were used to correlate Type D personality to side effects and adherence. In study III, the population consisted of pooled data from 1,167 subjects who had completed the ESS in five other studies. Ordinal regression and Rasch analysis were used to assess the existence of differential item functioning for age and gender. The cutoff for age was 65 years in the Rasch analysis. In study IV, SECI was sent to 186 subjects with newly diagnosed OSAS three times during the first year on CPAP. SECI results were followed over time within subjects, and were correlated to treatment dropout during the first year and machine usage time after 6 months.

Results: SECI provides a valid and reliable instrument to measure side effects, and non-adherent patients have higher scores (i.e., were more bothered by side effects) than adherent patients (study I). Type D personality was prevalent in approximately 30 % of CPAP treated OSAS patients, and was associated to poorer objective and subjective adherence as well as more side effects (study II). Differential item functioning was present in items 3, 4 and 8 for age in both DIF analyses, and to gender in item 8 the Rasch analysis (study III). Dry mouth and increased number of awakenings were consistently associated to poorer adherence in CPAP treated patients. Side effects both emerged and resolved over time (study IV).

Conclusions: Differences in previous research regarding side effects and CPAP adherence might be explained by differences in how side effects and adherence are defined. While some side effects are related to adherence, others are not. Side effects are furthermore not stable over time, and might be related to personality. ESS scores are also related to CPAP adherence according to previous research, but might be affected by other factors than sleepiness, such as age and possibly gender.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 102 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1378
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-97475 (URN)978-91-7519-528-5 (ISBN)
Public defence
2013-10-04, Victoriasalen, Campus US, Linköpings universitet, Linköping, 09:00 (Swedish)
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Available from: 2013-09-13 Created: 2013-09-13 Last updated: 2013-09-13Bibliographically approved

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Ulander, MartinSvanborg, EvaJohansson, PeterBroström, Anders

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Clinical NeurophysiologyFaculty of Health SciencesDepartment of Neurophysiology UHLNursing ScienceDepartment of Cardiology UHL
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