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Do ‘sleepy’ and ‘tired’ go together? Rasch analysis of the relationships between sleepiness, fatigue and non-restorative sleep complaints in a non-clinical population sample.
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Objective:
The lack of distinction in the clinical use of terms like fatigue and sleepiness is an important issue. While both fatigue and sleepiness can potentially be associated to non-restorative sleep (NRS) complaints, their relationships are still poorly described. We propose to use Rasch-analysis based methods to study the interrelations of fatigue, sleepiness and NRS.
Methods:
150 subjects (mean age 39.3, 18-65) from a community sample underwent a structured computer assisted web-interview. We assessed demographic data, sleep habits, subjective fatigue with the Fatigue Severity Scale (FSS), global and situational sleepiness with the Epworth (ESS) and the Stanford Sleepiness Scales respectively and affective symptoms with the Hospital Anxiety and Depression Scale. Dimensionality, measurement invariance and common person equating were investigated to study the FSS, the ESS and their relations to NRS.
Results:
NRS was linked to shorter habitual sleep duration and to higher scores on psychometric scales. Both sleepiness and daytime fatigue were positively correlated to each other and to the intensity of affective symptoms. Rasch analyses showed both the ESS and the FSS to measure uni-dimensional concepts of sleepiness and fatigue respectively. In contrast to the FSS, the ESS only showed partial invariance to a NRS complaint. Common person equating suggests that, despite similar Rasch-derived agreeability scores, fatigue and sleepiness (as measured by the FSS and the ESS) designate nevertheless distinct constructs.
Conclusion:
NRS complaints can simultaneously present with higher daytime fatigue and sleepiness levels but the associative relationships between fatigue and sleepiness remain relatively unaffected from NRS. Although participants presented a possible failure of adequate differentiation, fatigue and sleepiness seem to relate to different underlying concepts.
The lack of distinction in the clinical use of terms like fatigue and sleepiness is an important issue. While both fatigue and sleepiness can potentially be associated to non-restorative sleep (NRS) complaints, their relationships are still poorly described. We propose to use Rasch-analysis based methods to study the interrelations of fatigue, sleepiness and NRS.
Methods:
150 subjects (mean age 39.3, 18-65) from a community sample underwent a structured computer assisted web-interview. We assessed demographic data, sleep habits, subjective fatigue with the Fatigue Severity Scale (FSS), global and situational sleepiness with the Epworth (ESS) and the Stanford Sleepiness Scales respectively and affective symptoms with the Hospital Anxiety and Depression Scale. Dimensionality, measurement invariance and common person equating were investigated to study the FSS, the ESS and their relations to NRS.
Results:
NRS was linked to shorter habitual sleep duration and to higher scores on psychometric scales. Both sleepiness and daytime fatigue were positively correlated to each other and to the intensity of affective symptoms. Rasch analyses showed both the ESS and the FSS to measure uni-dimensional concepts of sleepiness and fatigue respectively. In contrast to the FSS, the ESS only showed partial invariance to a NRS complaint. Common person equating suggests that, despite similar Rasch-derived agreeability scores, fatigue and sleepiness (as measured by the FSS and the ESS) designate nevertheless distinct constructs.
Conclusion:
NRS complaints can simultaneously present with higher daytime fatigue and sleepiness levels but the associative relationships between fatigue and sleepiness remain relatively unaffected from NRS. Although participants presented a possible failure of adequate differentiation, fatigue and sleepiness seem to relate to different underlying concepts.
Tijdschrift: Neuroepidemiology
ISSN: 0251-5350
Issue: 1
Volume: 35
Pagina's: 1-11
Jaar van publicatie:2010
Trefwoorden:fatigue, sleepiness, non-restorative sleep