title: Variability of cognitive performance during hemodialysis: standardization of cognitive assessment.
abstract: OBJECTIVE
  Up to 70% of hemodialysis patients over the age of 54 have relevant cognitive impairment. No standardized protocol for the evaluation and monitoring of this population is available today. We hypothesized that the dialysis procedure and the testing environment induce fluctuations of cognitive performance.
  
  
  METHODS
  26 hemodialysis patients were randomly tested using the Montreal Cognitive Assessment (MoCA) before, during and after hemodialysis and inside the dialysis room or alone in a separate room. Tests were performed at weekly intervals using five test variations to prevent learning effects. The Mini-Mental State Examination (MMSE) was performed as a reference test.
  
  
  RESULTS
  MoCA scores significantly differed between the conditions: 'before hemodialysis' revealed the best MoCA score as compared to 'during hemodialysis' or 'after hemodialysis' (p = 0.013). During the combined condition 'before dialysis AND separate room', best performance was achieved (p < 0.001). The BP decline had no significant influence on cognitive performance, whereas the fluid shift showed a significant impact (p = 0.008).
  
  
  CONCLUSIONS
  Cognitive performance in hemodialysis patients highly depends on the time point and testing environment. Therefore, we strongly suggest a standardization, using the MoCA before hemodialysis in a separate room, in order to make testing results of future research in this field comparable.
authors.affiliation: Department of Nephrology, Klinikum rechts der Isar, Technische Universität München, Munich, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Tholen
authors.forename: Christoph
authors.initials: C
authors.lastname: Schmaderer
authors.forename: Ekatharina
authors.initials: E
authors.lastname: Kusmenkov
authors.forename: Stefan
authors.initials: S
authors.lastname: Chmielewski
authors.forename: Hans
authors.initials: H
authors.lastname: Förstl
authors.forename: Victoria
authors.initials: V
authors.lastname: Kehl
authors.forename: Uwe
authors.initials: U
authors.lastname: Heemann
authors.forename: Marcus
authors.initials: M
authors.lastname: Baumann
authors.forename: Timo
authors.initials: T
authors.lastname: Grimmer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003071:Cognition / Q000502:physiology*; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D003951:Diagnostic Errors / Q000517:prevention & control*; D004777:Environment; D005260:Female; D006801:Humans; D007361:Intelligence Tests / Q000592:standards; D008297:Male; D008609:Mental Status Schedule; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000592:standards; D011044:Poland; D012015:Reference Standards; D006435:Renal Dialysis / Q000009:adverse effects / Q000523:psychology; D013997:Time Factors