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 →
Spotted an error in this entry? Report it →