Omdal, Roald, Lenning, Ole Bernt, Jonsson, Grete et al. · Brain, behavior, & immunity - health · 2026 · DOI
A study of 48 people with long-COVID and 48 recovered controls found that fatigue was much more severe in the long-COVID group, but common blood markers of inflammation and cellular stress did not differ between the groups. This suggests that the fatigue in long-COVID may not be driven by the types of inflammation typically measured in blood tests, though the researchers note their findings are preliminary and limited to the biomarkers they tested.
By analogy, this finding may be relevant to ME/CFS, where fatigue similarly persists despite normalisation of conventional inflammatory markers. The study challenges the assumption that peripheral blood biomarkers alone can explain severe fatigue in post-infectious conditions, suggesting that future research—including in ME/CFS—may need to explore mechanisms beyond systemic inflammation.
This study does not establish that inflammation plays no role in long-COVID fatigue; it shows only that the specific peripheral blood biomarkers measured were not significantly associated with fatigue severity. It does not prove or disprove the existence of central nervous system-confined neuroinflammation, epigenetic changes, or other proposed mechanisms. The findings do not generalise to other biomarkers not measured, nor do they establish causation between any unmeasured factor and fatigue.
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
Omdal, Roald, Lenning, Ole Bernt, Jonsson, Grete, Kvaløy, Jan Terje, Skoie, Inger Marie, Braut, Geir Sverre, et al. (2026). Persistent fatigue in long-COVID is not associated with peripheral inflammatory or cellular stress biomarkers: A cross-sectional controlled study.. Brain, behavior, & immunity - health. https://doi.org/10.1016/j.bbih.2026.101226
BibTeX
@article{mecfsatlas-omdal-2026-persistent-fatigue,
author = {Omdal, Roald and Lenning, Ole Bernt and Jonsson, Grete and Kvaløy, Jan Terje and Skoie, Inger Marie and Braut, Geir Sverre and Grimstad, Tore},
title = {Persistent fatigue in long-COVID is not associated with peripheral inflammatory or cellular stress biomarkers: A cross-sectional controlled study.},
journal = {Brain, behavior, & immunity - health},
year = {2026},
doi = {10.1016/j.bbih.2026.101226},
note = {PubMed: 42004496},
url = {https://www.mecfsatlas.com/evidence/omdal-2026-persistent-fatigue},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-04-26. https://www.mecfsatlas.com/evidence/omdal-2026-persistent-fatigue
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