Williams, G, Pirmohamed, J, Minors, D et al. · Clinical physiology (Oxford, England) · 1996 · DOI
This study looked at whether the internal body clocks of ME/CFS patients work normally. Researchers measured body temperature and melatonin (a sleep hormone) rhythms in 20 ME/CFS patients and 17 healthy people. They found that in healthy people, body temperature and melatonin rhythms are normally synchronized, but in ME/CFS patients, these two rhythms were disconnected from each other—like two clocks running at different times.
Understanding circadian dysfunction in ME/CFS could explain why patients experience persistent fatigue, cognitive impairment, and concentration difficulties. If circadian dysrhythmia is a key mechanism, it could open new treatment avenues—such as chronotherapy or light exposure protocols—already used effectively in shift workers and jet-lag management.
This study does not prove that circadian dysrhythmia causes ME/CFS symptoms; it only shows an association in this small sample. The cross-sectional design cannot determine whether the circadian desynchronization is a primary driver of illness or a consequence of the behavioral and activity changes that accompany CFS. The authors themselves note that sleep deprivation, inactivity, and social disruption may be responsible for the dysrhythmia, rather than the reverse.
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 →
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