بررسی اعتبار مقیاس خستگی در سندرم خستگی مزمن

The Chalder fatigue scale is widely used to measure physical and mental fatigue in chronic fatigue syndrome patients, but the constructs of the scale have not been examined in this patient sample. We examined the constructs of the 14-item fatigue scale in a sample of 136 chronic fatigue syndrome patients through principal components analysis, followed by correlations with measures of subjective and objective cognitive performance, physiological measures of strength and functional work capacity, depression, anxiety, and subjective sleep difficulties. There were four factors of fatigue explaining 67% of the total variance. Factor 1 was correlated with subjective everyday cognitive difficulties, concentration difficulties, and a deficit in paired associate learning. Factor 2 was correlated with difficulties in maintaining sleep. Factor 3 was inversely correlated with grip strength, peak VO2, peak heart rate, and peak functional work capacity. Factor 4 was correlated with interview and self-rated measures of depression. The results support the validity of mental and physical fatigue subscales and the dropping of the “loss of interest” item in the 11-item version of the fatigue scale.

Chalder et al. [1] developed a brief self-rated 14-item instrument that measures the symptoms of mental and physical fatigue that are thought to be pathognomonic to chronic fatigue syndrome (CFS) 2 and 3. The Chalder fatigue scale has been used recently in treatment outcome studies in CFS patients 4 and 5. The validity and reliability of their scale has been examined in general practice attenders [1], but not before in CFS patients. However, inspection of the scale raises some questions concerning the validity of some items and its subdivision into physical (eight items) and mental fatigue subscales (six items). For instance, the mental fatigue item “loss of interest” is a cardinal symptom of depression [6]. The item “feeling sleepy or drowsy” could be related to problems with maintaining sleep at night [7] rather than physical fatigue items related to loss of stamina or strength, or mental fatigue symptoms such as poor concentration and word-finding difficulties. The physical fatigue subscale item “problems starting things” could be due to loss of motivation or an inability to organize oneself instead of a physical problem. We examined the validity of the constructs of physical and mental fatigue of the 14-item Chalder fatigue scale against a variety of subjective and objective measures of physical and mental functioning and mood and sleep disturbance.