Sleep-wake behavior in chronic fatigue syndrome

Sleep. 2011 May 1;34(5):671-8. doi: 10.1093/sleep/34.5.671.


Study objectives: Disturbances of the internal biological clock manifest as fatigue, poor concentration, and sleep disturbances-symptoms reminiscent of chronic fatigue syndrome (CFS) and suggestive of a role for circadian rhythm disturbance in CFS. We examined circadian patterns of activity, sleep, and cortisol secretion in patients with CFS.

Design: Case-control study, 5-day behavioral observation.

Setting: Natural setting/home environment

Participants: 15 patients with CFS and 15 healthy subjects of similar age, sex, body mass index (BMI), and activity levels.

Interventions: N/A.

Measurements: Self-report questionnaires were used to obtain medical history and demographic information and to assess health behaviors, somatic and psychological symptoms, and sleep quality. An actiwatch accelerometer recorded activity and sleep patterns over 5 days with concurrent activity and symptom logs. Diurnal salivary cortisol secretion was measured. Additionally, overnight heart rate monitoring and pain sensitivity assessment was undertaken.

Results: Ratings of symptoms, disability, sleep disturbance, and pain sensitivity were greater in patients with CFS. No between-group differences were found in the pattern or amount of sleep, activity, or cortisol secretion. Afternoon activity levels significantly increased evening fatigue in patients but not control subjects. Low nocturnal heart rate variability was identified as a biological correlate of unrefreshing sleep.

Conclusions: We found no evidence of circadian rhythm disturbance in CFS. However, the role of autonomic activity in the experience of unrefreshing sleep warrants further assessment. The activity symptom-relationship modelled here is of clinical significance in the approach to activity and symptom management in the treatment of CFS.

Keywords: Circadian rhythms; actigraphy; chronic fatigue syndrome; heart rate variability; unrefreshing sleep.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actigraphy
  • Adult
  • Case-Control Studies
  • Circadian Rhythm / physiology*
  • Fatigue Syndrome, Chronic / physiopathology*
  • Female
  • Heart Rate / physiology
  • Humans
  • Hydrocortisone / analysis
  • Male
  • Pain / physiopathology
  • Pain Measurement
  • Regression Analysis
  • Saliva / chemistry
  • Sleep / physiology
  • Sleep Initiation and Maintenance Disorders / physiopathology
  • Surveys and Questionnaires


  • Hydrocortisone