Background. Chronic fatigue syndrome (CFS) patients often
complain that they are more
susceptible to acute mental fatigue. It is important to determine whether
this is observed using
objective tests of sustained attention and responding.
Methods. Sixty-seven patients who fulfilled the criteria for
CFS proposed by Sharpe et al. (1991)
were compared with 126 matched healthy controls. Acute fatigue was assessed
by comparing
performance at the start and end of a lengthy test session and by examining
changes over the course
of individual 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 the test session.
Conclusions. The present results show that CFS patients are
more susceptible to acute fatigue than
healthy controls. This could reflect motor fatigue or an inability to compensate
for fatigue with
increased effort. This profile is consistent with previous research on
fatigue and suggests that
interpretation of certain aspects of CFS may be helped by considering it
as the end point of a
continuum of fatigue rather than a distinct disease.