Bailes, Sally, Libman, Eva, Baltzan, Marc et al. · Journal of psychosomatic research · 2006 · DOI
Doctors and patients often use the words 'sleepiness' and 'fatigue' interchangeably, but they actually describe different experiences. This study created two short, separate questionnaires—one to measure sleepiness (the urge to sleep) and one to measure fatigue (overall exhaustion)—by pulling items from existing popular fatigue and sleepiness scales. Testing these new scales on people with ME/CFS, narcolepsy, and healthy controls showed they measure distinct conditions that may respond to different treatments.
ME/CFS is often characterized by severe fatigue, yet clinicians may conflate this with sleepiness or sleep disorders. This study provides evidence-based tools to distinguish true fatigue from sleepiness, enabling more accurate diagnosis and targeted treatment. For ME/CFS patients specifically, differentiating fatigue from sleep-related symptoms could improve clinical management and reduce misdiagnosis.
This study does not establish prevalence of sleepiness versus fatigue in ME/CFS populations, nor does it determine which treatment interventions work best for each symptom type. The small ME/CFS sample (n=19) limits generalizability, and the cross-sectional design cannot establish whether these scales predict treatment outcomes or long-term disease course.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Bailes, Sally, Libman, Eva, Baltzan, Marc, Amsel, Rhonda, Schondorf, Ron, & Fichten, Catherine S (2006). Brief and distinct empirical sleepiness and fatigue scales.. Journal of psychosomatic research. https://doi.org/10.1016/j.jpsychores.2005.08.015
BibTeX
@article{mecfsatlas-bailes-2006-brief-distinct,
author = {Bailes, Sally and Libman, Eva and Baltzan, Marc and Amsel, Rhonda and Schondorf, Ron and Fichten, Catherine S},
title = {Brief and distinct empirical sleepiness and fatigue scales.},
journal = {Journal of psychosomatic research},
year = {2006},
doi = {10.1016/j.jpsychores.2005.08.015},
note = {PubMed: 16731235},
url = {https://www.mecfsatlas.com/evidence/bailes-2006-brief-distinct},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-25. https://www.mecfsatlas.com/evidence/bailes-2006-brief-distinct
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