Fatt, Scott J, Beilharz, Jessica E, Joubert, Michael et al. · Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine · 2020 · DOI
This study found that people with ME/CFS have reduced calming nervous system activity during deep sleep, compared to healthy people. This overactive state during sleep—even when the brain should be resting—is linked to poor sleep quality and feeling unwell. The findings suggest that the body's inability to fully relax during sleep may be a key problem in ME/CFS.
Unrefreshing sleep is a core symptom of ME/CFS, and this study identifies a specific neurophysiological mechanism—autonomic hypervigilance during deep sleep—that may explain why patients feel unrestored. Understanding this mechanism could guide new therapeutic interventions targeting sleep restoration in ME/CFS.
This study does not establish causation; reduced parasympathetic activity during sleep may be a consequence rather than a cause of poor sleep quality and wellbeing in ME/CFS. The cross-sectional design cannot determine whether correcting parasympathetic dysfunction would improve symptoms. Additionally, findings may not generalize to all ME/CFS patients or to different disease stages.
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
Fatt, Scott J, Beilharz, Jessica E, Joubert, Michael, Wilson, Chloe, Lloyd, Andrew R, Vollmer-Conna, Uté, et al. (2020). Parasympathetic activity is reduced during slow-wave sleep, but not resting wakefulness, in patients with chronic fatigue syndrome.. Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine. https://doi.org/10.5664/jcsm.8114
BibTeX
@article{mecfsatlas-fatt-2020-parasympathetic-activity,
author = {Fatt, Scott J and Beilharz, Jessica E and Joubert, Michael and Wilson, Chloe and Lloyd, Andrew R and Vollmer-Conna, Uté and Cvejic, Erin},
title = {Parasympathetic activity is reduced during slow-wave sleep, but not resting wakefulness, in patients with chronic fatigue syndrome.},
journal = {Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine},
year = {2020},
doi = {10.5664/jcsm.8114},
note = {PubMed: 31957647},
url = {https://www.mecfsatlas.com/evidence/fatt-2020-parasympathetic-activity},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-27. https://www.mecfsatlas.com/evidence/fatt-2020-parasympathetic-activity
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