Changes in measures of cognitive function in patients with end-stage kidney disease on dialysis and the effect of dialysis vintage: A longitudinal cohort study

Introduction: Prevalence of cognitive impairment increases with worsening severity of chronic kidney disease (CKD) and the majority of end-stage kidney disease (ESKD) patients on dialysis have cognitive impairment. Trends of cognitive function (CF) in this population are less well known with published studies reporting conflicting results. Methods: We assessed CF in a cohort of non-dialysis CKD and ESKD patients undergoing dialysis using modified mini-mental state examination (3MS), trail-making test (TMT-A & B) scores and Stroop task, and evaluated demographics, comorbidities, and depression using Beck depression inventory at baseline. We repeated tests of CF and depression > 1-year after baseline in both groups and compared change scores in CF and depression between ESKD/ CKD sub-groups. Among ESKD patients we compared change scores between patients with dialysis vintage of 1-year. Analysis of covariance was used to adjust for the effect of age on these change scores. Results: At baseline (N=211), compared to CKD (N=108), ESKD (N=103) patients had significantly worse CF based on 3MS and TMT-A & B scores, and depression scores. On follow-up (N=160) 3MS scores, especially the memory subscale significantly improved in ESKD, but worsened in CKD, with no significant changes in TMT A /TMT-B, or depression scores after adjusting for age. Among ESKD patients, 3MS, especially memory subscale improved in patients with dialysis vintage 1-year. The 51 patients who discontinued after baseline assessment had worse baseline CF scores suggesting differential attrition. Conclusion: Though baseline cognitive scores were worse in ESKD patients on dialysis, compared to CKD, their 3MS, especially memory subscale improved on follow-up. Among ESKD patients, the improvement was significant only in patients who have been on dialysis for less than one year which may indicate a beneficial effect of clearance of uraemic toxins. Differential attrition of study subjects may have impacted the observed results.Data were collected by research assistants by patient interviews and administering validated test instruments. Data were entered into an excel spreadsheet by research assistants. The data were analyzed using Stata 16.0