Meyer-Arndt, Lil, Pierchalla, Greta, Mödl, Lukas et al. · Brain, behavior, & immunity - health · 2025 · DOI
This study followed 45 long-COVID patients over 28 months to understand the connection between smell problems and fatigue, including those who developed ME/CFS. Researchers tested how well patients could smell (detecting scent strength, telling scents apart, and identifying them) and measured their fatigue, thinking ability, and physical strength. Most patients' smell improved over time, but problems with identifying specific smells lasted the longest, and patients with better smell discrimination at the start tended to feel better and function better after 20 months.
This research identifies olfactory identification as a potentially persistent marker of post-COVID neurological dysfunction and suggests it may correlate with long-term cognitive and functional outcomes. For ME/CFS patients, understanding that smell problems reflect central nervous system processing difficulties could validate this overlooked symptom and potentially guide early intervention strategies based on olfactory function patterns.
This study demonstrates correlation between olfactory dysfunction and cognitive/physical impairment but does not prove causation or identify the underlying mechanism. The findings apply primarily to mild-to-moderate cases and cannot establish whether olfactory testing would be a reliable diagnostic tool for ME/CFS across all severity levels or different patient populations. Additionally, improvement in smell does not prove that the same central processing deficits resolve in other domains.
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
Meyer-Arndt, Lil, Pierchalla, Greta, Mödl, Lukas, Wohlrab, Felix, Legler, Franziska, Hoppmann, Uta, et al. (2025). Functional olfactory impairment and fatigue in post-COVID-19 syndrome including ME/CFS - a longitudinal prospective observational study.. Brain, behavior, & immunity - health. https://doi.org/10.1016/j.bbih.2025.101124
BibTeX
@article{mecfsatlas-meyer-arndt-2025-functional-olfactory,
author = {Meyer-Arndt, Lil and Pierchalla, Greta and Mödl, Lukas and Wohlrab, Felix and Legler, Franziska and Hoppmann, Uta and Kedor, Claudia and Wittke, Kirsten and Freitag, Helma and Konietschke, Frank and Olze, Heidi and Paul, Friedemann and Scheibenbogen, Carmen and Bellmann-Strobl, Judith and Förster-Ruhrmann, Ulrike},
title = {Functional olfactory impairment and fatigue in post-COVID-19 syndrome including ME/CFS - a longitudinal prospective observational study.},
journal = {Brain, behavior, & immunity - health},
year = {2025},
doi = {10.1016/j.bbih.2025.101124},
note = {PubMed: 41281896},
url = {https://www.mecfsatlas.com/evidence/meyer-arndt-2025-functional-olfactory},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/meyer-arndt-2025-functional-olfactory
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