Saurel, Maïtena, Fornasieri, Isabelle, Del Sordo, Giovanna C et al. · Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine · 2026 · DOI
This study observed that people with ME/CFS who wore sleep-tracking wristbands for a week showed poorer sleep quality and more night-to-night variability in how well they slept compared to matched controls—even though they spent more time in bed. The sleep pattern was unstable from night to night, which may be an important feature of ME/CFS sleep problems that laboratory studies (typically 1–2 nights) do not capture.
Sleep disturbance is a cardinal symptom of ME/CFS, yet most evidence comes from single- or two-night laboratory assessments. This study is the first to systematically quantify night-to-night sleep variability under real-life conditions, suggesting that sleep instability—not only poor quality—may be a clinically relevant dimension of ME/CFS sleep pathophysiology worth targeting in future interventions.
This study does not establish what causes the observed sleep variability or whether addressing it would improve overall ME/CFS outcomes. It does not clarify whether sleep instability drives other ME/CFS symptoms or is a consequence of them. The findings are associational only and do not support causal inference. The case definition quality is unknown, and the study does not indicate whether findings generalise to the full spectrum of ME/CFS severity.
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
Saurel, Maïtena, Fornasieri, Isabelle, Del Sordo, Giovanna C, Chatain, Cyril, Fantini, Maria Livia, Gruet, Mathieu, et al. (2026). Sleep in myalgic encephalomyelitis/chronic fatigue syndrome shows marked night-to-night fluctuation under free-living conditions-results from a matched case-control study.. Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine. https://doi.org/10.1007/s44470-026-00079-7
BibTeX
@article{mecfsatlas-saurel-2026-sleep-myalgic,
author = {Saurel, Maïtena and Fornasieri, Isabelle and Del Sordo, Giovanna C and Chatain, Cyril and Fantini, Maria Livia and Gruet, Mathieu and Saidi, Oussama},
title = {Sleep in myalgic encephalomyelitis/chronic fatigue syndrome shows marked night-to-night fluctuation under free-living conditions-results from a matched case-control study.},
journal = {Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine},
year = {2026},
doi = {10.1007/s44470-026-00079-7},
note = {PubMed: 42129014},
url = {https://www.mecfsatlas.com/evidence/saurel-2026-sleep-myalgic},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/saurel-2026-sleep-myalgic
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