Cognitive changes associated with switching to frequent nocturnal hemodialysis or renal transplantation

Abstract

Background: It is uncertain whether switching to frequent nocturnal hemodialysis improves cognitive function in well-dialyzed patients and how this compares to patients who receive a kidney transplant.

Methods: We conducted a multicenter observational study with longitudinal follow-up of the effect on cognitive performance of switching dialysis treatment modality from conventional thrice-weekly hemodialysis to frequent nocturnal hemodialysis, a functioning renal transplant or remaining on thrice-weekly conventional hemodialysis. Neuropsychological tests of memory, attention, psychomotor processing speed, executive function and fluency as well as measures of solute clearance were performed at baseline and again after switching modality. The change in cognitive performance measured by neuropsychological tests assessing multiple cognitive domains at baseline, 4 and 12 months after switching dialysis modality were analyzed using a linear mixed model.

Results: Seventy-seven patients were enrolled; 21 of these 77 patients were recruited from the randomized Frequent Hemodialysis Network (FHN) Nocturnal Trial. Of these, 18 patients started frequent nocturnal hemodialysis, 28 patients received a kidney transplant and 31 patients remained on conventional thrice-weekly hemodialysis. Forty-eight patients (62 %) returned for the 12-month follow-up. Despite a significant improvement in solute clearance, 12 months treatment with frequent nocturnal hemodialysis was not associated with substantial improvement in cognitive performance. By contrast, renal transplantation, which led to near normalization of solute clearance was associated with clinically relevant and significant improvements in verbal learning and memory with a trend towards improvements in psychomotor processing speed. Cognitive performance in patients on conventional hemodialysis remained stable with the exception of an improvement in psychomotor processing speed and a decline in verbal fluency.

Conclusions: In patients on conventional thrice-weekly hemodialysis, receiving a functioning renal transplant was associated with improvement in auditory-verbal memory and psychomotor processing speed, which was not observed after 12 months of frequent nocturnal hemodialysis.

Fig. 1

Patient flow diagram

Fig. 2

Change in selected cognitive tests at 4 and 12 months after switching to frequent nocturnal hemodialysis (circles, ○) receiving a renal transplant (triangles, ∆) or remaining on conventional thrice-weekly hemodialysis (squares, □). Data shows analysis after adjustment for difference in baseline characteristics as described in Additional file 2: Table S1. Refer to Table 1 and legend to Table 4 for a description of the tests and abbreviations. Dashed lines represent statistically significant (p < 0.05) within group changes in test performance between 12 months and baseline. Vertical lines with the associated p-value represent statistically significant (p < 0.05) pairwise differences between study groups at the specified study visit