Ohayon, Maurice M · Archives of internal medicine · 2005 · DOI
This study surveyed over 25,000 people across seven European countries to understand how common nonrestorative sleep (feeling unrefreshed after sleep) is and what factors are linked to it. Researchers found that about 1 in 10 people experience nonrestorative sleep, with women and younger adults affected more often. People with this symptom reported worse daytime tiredness and mental fatigue compared to those with other sleep problems.
Nonrestorative sleep is a cardinal feature of ME/CFS that has received limited epidemiological study. This large European study establishes NRS as a distinct symptom producing significant daytime impairment (fatigue, irritability, cognitive dysfunction) and validates its association with psychiatric comorbidities—findings directly relevant to understanding ME/CFS symptom burden and disease mechanisms.
This cross-sectional design cannot establish causation or elucidate mechanistic links between NRS and associated conditions like depression or anxiety. The study does not differentiate NRS occurring in ME/CFS specifically from NRS in other conditions, and geographic variation may reflect cultural, healthcare access, or reporting differences rather than true prevalence differences.
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
Ohayon, Maurice M (2005). Prevalence and correlates of nonrestorative sleep complaints.. Archives of internal medicine. https://doi.org/10.1001/archinte.165.1.35
BibTeX
@article{mecfsatlas-ohayon-2005-prevalence-correlates,
author = {Ohayon, Maurice M},
title = {Prevalence and correlates of nonrestorative sleep complaints.},
journal = {Archives of internal medicine},
year = {2005},
doi = {10.1001/archinte.165.1.35},
note = {PubMed: 15642872},
url = {https://www.mecfsatlas.com/evidence/ohayon-2005-prevalence-correlates},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-25. https://www.mecfsatlas.com/evidence/ohayon-2005-prevalence-correlates
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