Symptom Fluctuations and Daily Physical Activity in Patients With Chronic Fatigue Syndrome: A Case-Control Study

Meeus M, van Eupen I, van Baarle E, De Boeck V, Luyckx A, Kos D, Nijs J. Symptom fluctuations and daily physical activity in patients with chronic fatigue syndrome: a case-control study.ObjectivesTo compare the activity pattern of patients with chronic fatigue syndrome (CFS) with healthy sedentary subjects and examine the relationship between the different parameters of performed activity (registered by an accelerometer device) and symptom severity and fluctuation (registered by questionnaires) in patients with CFS.DesignCase-control study. Participants were asked to wear an accelerometer device on the nondominant hand for 6 consecutive days. Every morning, afternoon, and evening patients scored the intensity of their pain, fatigue, and concentration difficulties on a visual analog scale.SettingPatients were recruited from a specialized chronic fatigue clinic in the university hospital, where all subjects were invited for 2 appointments (for questionnaire and accelerometer adjustments). In between, activity data were collected in the subject's normal home environment.ParticipantsFemale patients (n=67) with CFS and female age-matched healthy sedentary controls.InterventionsNot applicable.Main Outcome MeasuresAccelerometry (average activity counts, peak activity counts, ratio peak/average, minutes spent per activity category) and symptom severity (intensity of pain, fatigue, and concentration difficulties).ResultsPatients with CFS were less active, spent more time sedentary, and less time lightly active (P<.05). The course of the activity level during the registration period (P interaction>.05), peak activity, and the staggering of activities (ratio peak/average) on 1 day were not different between groups (P>.05). Negative correlations (–.242 varying to –.307) were observed for sedentary activity and the ratio with symptom severity and variation on the same and the next day. Light, moderate, and vigorous, as well as the average activity and the peak activity, were positively correlated (.242 varying to .421) with symptom severity and variation.ConclusionsThe more patients with CFS are sedentary and the better activity is dispersed, the fewer symptoms and variations they experience on the same and next day. Inversely, more symptoms and variability is experienced when patients were more active that day or the previous day. The direction of these relations cannot be determined in a cross-sectional study and requires further study.