Cognitive Function, Access to Kidney Transplantation, and Waitlist Mortality Among Kidney Transplant Candidates With or Without Diabetes

Abstract

Rationale & objective: Intact cognition is generally a prerequisite for navigating through and completing evaluation for kidney transplantation. Despite kidney transplantation being contraindicated for those with severe dementia, screening for more mild forms of cognitive impairment before referral is rare. Candidates may have unrecognized cognitive impairment, which may prolong evaluation, elevate mortality risk, and hinder access to kidney transplantation. We estimated the burden of cognitive impairment and its association with access to kidney transplantation and waitlist mortality.

Study design: Prospective cohort study.

Setting & participants: 3,630 participants (January 2009 to June 2018) with cognitive function measured (by the Modified Mini-Mental State Examination [3MS]) at kidney transplantation evaluation at 1 of 2 transplantation centers.

Predictors: Cognitive impairment (3MS score<80).

Outcomes: Listing, waitlist mortality, and kidney transplantation.

Analytical approach: We estimated the adjusted chance of listing (Cox regression), risk for waitlist mortality (competing-risks regression), and kidney transplantation rate (Poisson regression) by cognitive impairment. Given potential differences in cause of cognitive impairment among those with and without diabetes, we tested whether these associations differed by diabetes status using a Wald test.

Results: At evaluation, 6.4% of participants had cognitive impairment, which was independently associated with 25% lower chance of listing (adjusted HR, 0.75; 95% CI, 0.61-0.91); this association did not differ by diabetes status (P_interaction=0.07). There was a nominal difference by diabetes status for the association between cognitive impairment and kidney transplantation rate (P_interaction=0.05), while the association between cognitive impairment and waitlist mortality differed by diabetes status kidney transplantation rates (P_interaction=0.02). Among candidates without diabetes, those with cognitive impairment were at 2.47 (95% CI, 1.31-4.66) times greater risk for waitlist mortality; cognitive impairment was not associated with this outcome among candidates with diabetes.

Limitations: Single measure of cognitive impairment.

Conclusions: Cognitive impairment is associated with a lower chance of being placed on the waitlist, and among patients without diabetes, with increased mortality on the waitlist. Future studies should investigate whether implementation of screening for cognitive impairment improves these outcomes.

Keywords: Cognitive impairment; cognitive function testing; dementia; diabetes; dialysis; end-stage renal disease (ESRD); functional dependence; health literacy; mental capacity; renal transplantation; transplant candidate; waitlisting.