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Cognitive dysfunction relates to subjective report of mental fatigue in patients with chronic fatigue syndrome

Capuron L, Welberg L, Heim C, Wagner D, Solomon L, Papanicolaou DA, Craddock RC, Miller AH, Reeves WC
Neuropsychopharmacology Online publication: 10 November 2005 at http://www.acnp.org/citations/Npp111005050502/default.pdf

Summary

Between 50% and 85% of patients with chronic fatigue syndrome ( CFS) report memory and concentration difficulties that contribute considerably to social and occupational dysfunction. However, CFS patients do not uniformly have objective evidence of impaired cognitive function. It may be (as suggested in our recent modeling study) that patients’ perception of impaired cognition reflects mental fatigue. This study evaluated the relationship between mental fatigue and cognitive function in 43 people with CFS and 53 healthy controls identified from the general population of Wichita. Study subjects participated in a 2-day in-hospital study. We defined CFS by empirical application of the 1994 criteria. We measured mental fatigue, using the mental fatigue subscale of the multidimensional fatigue inventory ( MFI), and evaluated cognitive function by means of the Cambridge neuropsychological test automated battery (CANTAB). We found no significant differences in cognitive function between people with CFS and well controls. However, persons with CFS had significantly worse mental fatigue scores (on the MFI) than controls, and this was significantly associated with objective measures of working memory and cognitive fatigability (by CANTAB). As in the interferon-α modeling study, this finding suggests that the impaired concentration experienced by those suffering from CFS reflects a greater mental effort to maintain performance.

Abstract

Purpose : Autonomic nervous system dysfunction has been suggested as involved in the pathophysiology of chronic fatigue syndrome. This population-based case control study addressed the potential association between orthostatic instability (one sign of dysautonomia) and chronic fatigue syndrome.

Subjects and Methods : Fifty-eight subjects who fulfilled criteria of the 1994 chronic fatigue syndrome research case definition and 55 healthy controls participated in a 2-day inpatient evaluation. Subjects had been identified during a 4-year population-based chronic fatigue syndrome surveillance study in Wichita, Kan. The present study evaluated subjects’ current medical and psychiatric status, reviewed past medical/psychiatric history and medication use, used a stand-up test to screen for orthostatic instability, and conducted a head-up tilt table test to diagnose orthostatic instability.

Results : No one manifested orthostatic instability in the stand-up test. The head-up tilt test elicited orthostatic instability in 30% of eligible chronic fatigue syndrome subjects (all with postural orthostatic tachycardia) and 48% of controls (50% with neurally mediated hypotension); intolerance was present in only nonfatigued (n = 7) subjects. Neither fatigue nor illness severity were associated with outcome.

Conclusions : Orthostatic instability was similar in persons with chronic fatigue syndrome and nonfatigued controls subjects recruited from the general Wichita population. Delayed responses to head-up tilt tests were common and may reflect hydration status. These findings suggest reappraisal of primary dysautonomia as a factor in the pathogenesis of chronic fatigue syndrome.

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