Acute fatigue in chronic fatigue syndrome patients

Background. Chronic fatigue syndrome (CFS) patients often complain that the y are more susceptible to acute mental fatigue. It is important to determin e whether this is observed using objective tests of sustained attention and responding. Methods. Sixty-seven patients who fulfilled the criteria for CFS proposed b y Sharpe et ttl. (1991) were compared with 126 matched healthy controls. Ac ute fatigue was assessed by comparing performance at the start and end of a lengthy test session and by examining changes over the course of individua l tasks. Results. CFS patients showed impaired performance compared to the controls and these differences increased as the volunteers developed acute fatigue. In addition, differences between the two groups were larger at the end of t he test session. Conclusions. The present results show that CFS patients are more susceptibl e to acute fatigue than healthy controls. This could reflect motor fatigue or an inability to compensate for fatigue with increased effort. This profi le is consistent with previous research on fatigue and suggests that interp retation of certain aspects of CFS may be helped by considering it as the e nd point of a continuum of fatigue rather than a distinct disease.