Menzies, Victoria, Kelly, Debra L, Yang, Gee S et al. · Chronic illness · 2021 · DOI
This review looked at 10 studies examining whether fatigue and cognitive problems (like brain fog or memory issues) are connected in people with chronic diseases, including ME/CFS. The researchers found that in a few studies, higher fatigue was linked with worse cognitive function, but overall there isn't enough research yet to be certain about this relationship. More studies are needed to understand how fatigue and thinking problems relate to each other.
ME/CFS patients frequently report cognitive impairment ('brain fog') alongside fatigue, yet the mechanistic link remains poorly understood. This review identifies a significant gap in the literature and establishes that cognitive-fatigue associations warrant rigorous investigation as a priority for developing targeted treatments in ME/CFS.
This review does not establish whether fatigue *causes* cognitive impairment or vice versa—only that they are statistically correlated. The small number of included studies (particularly only 2 CFS studies) means findings may not reliably reflect the true relationship in ME/CFS populations. The review also does not identify the biological mechanisms underlying any observed associations.
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
Menzies, Victoria, Kelly, Debra L, Yang, Gee S, Starkweather, Angela, & Lyon, Debra E (2021). A systematic review of the association between fatigue and cognition in chronic noncommunicable diseases.. Chronic illness. https://doi.org/10.1177/1742395319836472
BibTeX
@article{mecfsatlas-menzies-2021-systematic-review,
author = {Menzies, Victoria and Kelly, Debra L and Yang, Gee S and Starkweather, Angela and Lyon, Debra E},
title = {A systematic review of the association between fatigue and cognition in chronic noncommunicable diseases.},
journal = {Chronic illness},
year = {2021},
doi = {10.1177/1742395319836472},
note = {PubMed: 30884965},
url = {https://www.mecfsatlas.com/evidence/menzies-2021-systematic-review},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/menzies-2021-systematic-review
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