title: Subjective fatigue is not associated with cognitive impairment in multiple sclerosis: cross-sectional and longitudinal analysis.
abstract: BACKGROUND
  Studies in multiple sclerosis (MS) report conflicting conclusions regarding fatigue and cognition, which may partly be due to the use of small sample sizes and frequent reliance on a cross-sectional approach.
  
  
  OBJECTIVE
  The ability to distinguish between these two disabling symptoms is necessary in order to properly assess and treat MS patients.
  
  
  METHODS
  In a retrospective analysis, we assessed the correlation between fatigue and neuropsychological (NP) testing using a cross-sectional (n = 465) and longitudinal approach (n = 69). Cognition was measured using a comprehensive battery called the Minimal Assessment of Cognitive Function in MS (MACFIMS), and fatigue was measured with the Fatigue Severity Scale (FSS). FSS scores were categorized as normal (<or=4.0), borderline fatigue (4 < FSS < 5.0), and fatigued (>or=5.0). Repeat assessments (n = 69) were categorized as improved or worsened by a change in FSS of either 0.5 or 1.0.
  
  
  RESULTS
  MS patients had significantly higher FSS scores than normal controls (P < 0.001). No correlation was found between FSS and NP scores in either cross-sectional or longitudinal analyses. Fatigue was moderately correlated with depression, assessed using the Beck Depression Inventory Fast Screen (BDIFS) (r = 0.44, P < 0.001). Longitudinally, there was a medium correlation between change in FSS and BDIFS (r = 0.34, P = 0.001), but no significant differences on NP scores using either definition of change.
  
  
  CONCLUSIONS
  We conclude that self-reported fatigue, while correlated with self-reported depression, is not significantly related to cognitive capacity in MS.
authors: School of Medicine, The Jacobs Neurological Institute, State University of New York at Buffalo, Buffalo, New York 14203, USA.
authors: S A
authors: SA
authors: Morrow
authors: B
authors: B
authors: Weinstock-Guttman
authors: F E
authors: FE
authors: Munschauer
authors: D
authors: D
authors: Hojnacki
authors: R H B
authors: RH
authors: Benedict
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000209:etiology* / Q000523:psychology; D003430:Cross-Sectional Studies; D003863:Depression / Q000209:etiology; D005221:Fatigue / Q000209:etiology* / Q000523:psychology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000150:complications* / Q000523:psychology; D009483:Neuropsychological Tests; D011237:Predictive Value of Tests; D012107:Research Design; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013997:Time Factors