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

BACKGROUND AND AIMS: Hemodialysis (HD) patients are educated and counseled during the HD procedure. There are few studies assessing whether cognitive performance varies with dialysis. METHODS: 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). RESULTS: 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. CONCLUSIONS: 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.