Cognitive performance before and during hemodialysis: a randomized cross-over trial

Hemodialysis (HD) patients are educated and counseled during the HD procedure. There are few studies assessing whether cognitive performance varies with dialysis.

Using a randomized cross-over design, 40 patients were assigned to one of two sequences: testing 1 h before dialysis followed 1 month later by testing during the first hour of dialysis (n = 21) versus testing during the first hour of dialysis followed 1 month later by 1 h before dialysis (n = 19). Cognitive tests were administered at each testing period. Mixed regression models evaluated for a dialysis effect (difference between test performance before vs. during dialysis) while adjusting for potential learning (difference between first and second tests).

In models accounting for period of testing, there was no difference in test performance between 1 h before versus during the first hour of HD for all administered cognitive tests (p > 0.05). A learning effect was detected between first and second test administration in two tests, specifically, the Word List Learning and the Digit Symbol Substitution Test.

We found no difference in cognitive performance depending on the time of testing, suggesting that cognitive tests performed during the first hour of dialysis are a valid assessment of cognitive performance.