Effect of a single dialysis session on cognitive function in CKD5D patients: a prospective clinical study

Nephrol Dial Transplant. 2015 Sep;30(9):1551-9. doi: 10.1093/ndt/gfv213. Epub 2015 Jun 11.


Background: Cognitive function declines in parallel to the decrease in glomerular filtration rate, best epitomized by the markedly reduced cerebral performance in patients undergoing maintenance haemodialysis [chronic kidney disease stage 5 dialysis (CKD5D)]. Aside from structural permanent damage, there seems to be a reversible part of low cognitive performance. The potential effect of a single dialysis session on cognitive function remains still elusive. The aim of the study was to assess cognitive function using a widespread test battery and avoiding excluding effects of circadian variations.

Methods: Twenty-eight medically stable CKD5D patients (age: 54.9 ± 13.2 years, dialysis vintage: 46.2 ± 51.0 month) at two tertiary care centres with outpatient dialysis units were enrolled. Cognitive testing was always performed twice within 24 h, 1 h prior to haemodialysis (T1pre-dialysis) as well as 19 h after the end of dialysis (T2post-dialysis) including assessment of memory, attention and concentration, executive functioning, word fluency and psychomotor speed by using a well-validated neuropsychological test battery. Patients were randomized into two groups. One group was examined before (T1pre-dialysis) and after (T2post-dialysis) Dialysis Session 1. The other group was first examined the day after Dialysis Session 1 (T2post-dialysis) and then before Dialysis Session 2 (T1pre-dialysis) in order to exclude potential learning effects. Twenty age-matched subjects with normal excretory renal function were used for comparison.

Results: Neuropsychological testing found that the CKD5D performed significantly worse on measures of alertness, attention, working memory, logical and visual memory, word fluency and executive functions compared with non-CKD subjects. No differences in short-term memory, selective attention, as well as problem-solving and planning were found between CKD5D patients and non-CKD subjects. A single haemodialysis session led to a significant improvement in logical (Rivermead Behaviour Memory Test story: P < 0.001) and visual memories [Rey-Osterrieth Complex Figure Test (RCFT) memory quotient: P < 0.001], psychomotor speed [Trail Making Test (TMT) B: P = 0.020], activity planning (executive functions) (RCFT copy/points deduction: P < 0.001) and concentration (TMT A: P < 0.001).

Conclusion: Our data demonstrate improvements in memory functions, executive functions and psychomotor abilities after a single dialysis session, pointing to a reversible component of low cognitive performance in CKD5D.

Keywords: neuropsychological tests; uraemic toxins.

Publication types

  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Case-Control Studies
  • Cognition / physiology*
  • Cognition Disorders / physiopathology*
  • Female
  • Humans
  • Male
  • Memory, Short-Term / physiology
  • Middle Aged
  • Neuropsychological Tests
  • Prospective Studies
  • Renal Dialysis*
  • Renal Insufficiency, Chronic / classification
  • Renal Insufficiency, Chronic / physiopathology*
  • Renal Insufficiency, Chronic / therapy*