Meeus, Mira, VAN Eupen, Inge, Hondequin, Jasmien et al. · In vivo (Athens, Greece) · 2010
This study examined whether a chemical messenger in the blood called nitric oxide (NO) is related to how active people are in ME/CFS. Researchers measured activity levels and blood NO in 30 ME/CFS patients and 29 healthy but inactive people over one week. While ME/CFS patients were indeed much less active than controls, the amount of NO in their blood was normal and had no connection to their activity levels.
This study helps clarify the biological basis of reduced activity in ME/CFS by ruling out nitric oxide dysregulation as a mechanistic link. Understanding what does not cause ME/CFS symptoms is as important as identifying what does, as it focuses future research on more promising biological pathways and prevents investigators from pursuing dead-ends.
This study does not prove that NO plays no role in ME/CFS pathology—only that NO levels are not abnormal and do not correlate with activity. It also does not explain the underlying cause of reduced activity in ME/CFS patients. The study measured peripheral blood NO only; local NO production in tissues or other forms of NO metabolism were not assessed.
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
Meeus, Mira, VAN Eupen, Inge, Hondequin, Jasmien, DE Hauwere, Lieve, Kos, Daphne, & Nijs, Jo (2010). Nitric oxide concentrations are normal and unrelated to activity level in chronic fatigue syndrome: a case-control study.. In vivo (Athens, Greece). https://pubmed.ncbi.nlm.nih.gov/21164046/
BibTeX
@article{mecfsatlas-meeus-2010-nitric-oxide,
author = {Meeus, Mira and VAN Eupen, Inge and Hondequin, Jasmien and DE Hauwere, Lieve and Kos, Daphne and Nijs, Jo},
title = {Nitric oxide concentrations are normal and unrelated to activity level in chronic fatigue syndrome: a case-control study.},
journal = {In vivo (Athens, Greece)},
year = {2010},
note = {PubMed: 21164046},
url = {https://www.mecfsatlas.com/evidence/meeus-2010-nitric-oxide},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/meeus-2010-nitric-oxide
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