Pretransplant Cognitive Function and Kidney Transplant Outcomes: A Prospective Cohort Study

Background & Hypothesis

Cognitive impairment is common in patients being evaluated for a kidney transplant (KT). The association between pretransplant cognitive function and posttransplant outcomes is unclear.

Study Design

We performed a prospective cohort study to assess the association between pretransplant cognitive function and clinically relevant posttransplant outcomes.

Setting and Population

In this single center study, participants from the transplant clinic were evaluated during their pretransplant clinic visits and followed prospectively.

Outcomes

Our primary outcome measure was allograft function. Secondary outcomes were length of hospitalization for KT, hospital readmission within 30 and 90 days, graft loss, graft rejection within 90 days and 1 year, and mortality.

Analytic Approach

We measured cognitive function with the Montreal Cognitive Assessment (MoCA) test. We assessed the association of pretransplant MoCA score with posttransplant outcomes; we used linear mixed effects models to assess the association with the change in estimated glomerular filtration rate, Poisson regression for length of hospitalization, Cox proportional hazard model for graft loss and mortality, and a logistic regression model for readmission and rejection.

Results

We followed 501 participants for 2.7 ± 1.5 years. The mean age of the patients was 53 ± 14 years and the mean pretransplant MoCA score was 25 ± 3. Lower pretransplant MoCA scores did not adversely affect the primary outcome of allograft function or the secondary outcomes. Although higher MoCA scores predicted a higher decline in graft function (β = −0.28, 95% CI: −0.55 to −0.01, P = 0.04), the effect was small and not clinically significant. Older age was associated with longer hospitalization, lower likelihood of rejection, and higher mortality. Deceased donor KT (vs living donor KT) was associated with longer hospitalization but better graft function. Longer time receiving dialysis before KT was associated with longer hospitalization. A history of diabetes mellitus was associated with higher mortality.

Limitations

Single center study limiting generalizability.

Conclusions

Pretransplant MoCA scores were not associated with the primary outcome of allograft function or the secondary outcomes.

Plain-Language Summary

Cognitive impairment (problems with memory and thinking) is common in patients with kidney disease. Cognitive impairment is associated with problems following instructions and remembering to take medications. Medical adherence is important in kidney transplant recipients, and inability to follow instructions and missed doses of immunosuppression increases the risk of rejection of the transplanted kidney. However, kidney transplantation also improves cognition. Hence, transplant centers wonder if cognitive impairment before transplant affects clinical outcomes after kidney transplant. We tried to answer this question by assessing cognitive function before transplantation and examining whether pretransplant cognitive function affects graft function, length of hospitalization, readmission after transplantation, rejection, and death. We did not find any strong link between cognitive function before transplant and these outcomes.