G.A Tooley & M.P. McCabe.
Dr Greg Tooley
School of Psychology,
221 Burwood Hwy,
Burwood, Vic 3125
The integrity of the circadian timekeeping system in chronic fatigue syndrome
Current evidence suggests that, rather than being a discrete disease entity with a single cause, CFS is a clinical condition resulting from the interaction of a number of pathophysiological factors, including acute infections, stress and psychiatric disorder. Recently, there has been some interest in the proposition that disordered circadian time-keeping may contribute to the development and/or course of the illness. The rationale for the investigation of circadian factors in CFS is based on the fact that disorders known to be associated with circadian dysregulation, such as jet lag and shift-work related syndromes have a high degree of symptomatological overlap with CFS. Also, the presence of circadian disturbance could account, in part, for other phenomenological aspects of CFS, including the high rates of comorbid affective disturbance, and the reports of low-level immune dyregulation among sufferers. This paper presents the findings of a series of three studies that compared the circadian patterns of sleep-activity, core temperature and melatonin secretion in CFS patients and healthy controls matched for sex and age. Results of study 1 (n=64) indicated that CFS patients' sleep-activity cycles were significantly phase delayed compared to controls, and that some aspects of their circadian profiles of sleep-activity were related to some measures of sleep-disturbance and well-being. Results of studies 2 and 3 (n=62) indicated that the circadian rhythms of sleep-wake, core temperature and melatonin secretion were less effectively synchronised in the CFS group. Further evidence was collected that suggested that there was a relationship between circadian parameters and symptom measures in the CFS group. These findings provide evidence that CFS is associated with a degree of both internal and external circadian desynchrony, although the clinical significance and specificity of the dysregulation remains to be determined. Findings also raise significant methodological issues for CFS research regarding the investigation of parameters that demonstrate circadian variation.
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