Hamilos, D L, Nutter, D, Gershtenson, J et al. · Clinical physiology (Oxford, England) · 2001 · DOI
Researchers wanted to know if ME/CFS might be caused by broken internal body clocks, similar to jet lag. They measured core body temperature continuously in 10 ME/CFS patients and 10 healthy controls over 48 hours and analyzed the patterns. The body temperature rhythms in ME/CFS patients looked almost identical to healthy people, suggesting a disrupted body clock is unlikely to be the main cause of ME/CFS symptoms.
This study directly tested a plausible biological mechanism—circadian disruption—that could explain ME/CFS fatigue, cognitive problems, and sleep issues. A null finding is valuable because it redirects research toward other pathological mechanisms and demonstrates that simple circadian misalignment is not the core problem in ME/CFS.
This study does not rule out circadian abnormalities in other biological systems (e.g., melatonin, cortisol, or heart rate variability), only core body temperature specifically. It also cannot account for possible circadian disturbances that emerge under different conditions (e.g., post-exertional or during acute relapse) or for post-translational circadian dysfunction. The small sample size (N=20) limits generalizability.
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
Hamilos, D L, Nutter, D, Gershtenson, J, Ikle, D, Hamilos, S S, Redmond, D P, et al. (2001). Circadian rhythm of core body temperature in subjects with chronic fatigue syndrome.. Clinical physiology (Oxford, England). https://doi.org/10.1046/j.1365-2281.2001.00321.x
BibTeX
@article{mecfsatlas-hamilos-2001-circadian-rhythm,
author = {Hamilos, D L and Nutter, D and Gershtenson, J and Ikle, D and Hamilos, S S and Redmond, D P and Di Clementi, J D and Schmaling, K B and Jones, J F},
title = {Circadian rhythm of core body temperature in subjects with chronic fatigue syndrome.},
journal = {Clinical physiology (Oxford, England)},
year = {2001},
doi = {10.1046/j.1365-2281.2001.00321.x},
note = {PubMed: 11318826},
url = {https://www.mecfsatlas.com/evidence/hamilos-2001-circadian-rhythm},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/hamilos-2001-circadian-rhythm
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