Neurocognitive deficits may not resolve following pediatric kidney transplantation

Abstract

Background Pediatric chronic kidney disease (CKD) patients are at risk for cognitive deficits with worsening disease progression. Limited, existing cross‐sectional studies suggest that cognitive deficits may improve following kidney transplantation. We sought to assess cognitive performance in relationship to kidney transplantation and kidney‐specific medical variables in a sample of pediatric kidney transplant patients who provided cross‐sectional and longitudinal observations. Methods A retrospective chart review was conducted in patients who completed pre‐ and/or post‐transplant neurocognitive testing at the University of Iowa from 2015–2021. Cognitive outcomes were investigated with developmentally appropriate, standardized measures. Mixed linear models estimated the impact of transplant status on cognitive function (z‐scores). Subsequent post‐hoc t‐tests on change scores were limited to patients who had provided pre‐ and post‐transplant assessments. Results Thirty eight patients underwent cognitive assessments: 10 had both pre‐ and post‐transplant cognitive assessments, 11 had pre‐transplant assessments only, and 17 had post‐transplant data only. Post‐transplant status was associated with significantly lower full‐scale IQ and slower processing speed compared to pre‐transplant status (estimate = −0.32, 95% confidence interval [CI] = −0.52: −0.12; estimate = −0.86, CI = −1.17: −0.55, respectively). Post‐hoc analyses confirmed results from the mixed models (FSIQ change score = −0.34, 95% CI = −0.56: −0.12; processing speed change score = −0.98, CI = −1.28: −0.68). Finally, being ≥80 months old at transplant was associated with substantially lower FSIQ compared to being <80 months (estimate = −1.25, 95% CI = −1.94: −0.56). Conclusions Our results highlight the importance of monitoring cognitive function following pediatric kidney transplant and identify older transplant age as a risk factor for cognitive deficits.

Understanding the impact of pediatric kidney transplantation on cognition: A review of the literature

“…33 These findings were further supported by longitudinal post-hoc analyses which indicated change in FSIQ and nonverbal scores decreased significantly from pre-to posttransplant in nine individuals. 33 Furthermore, disease-related factors may increase the risk for deficits in IQ post-transplant. Lower IQ in pediatric KT recipients has been associated with earlier age of dialysis onset, longer dialysis and pre-transplant duration, and older age at transplant.…”

“…Cross‐sectional data demonstrate persistence of low‐average IQ scores 23,24 —or even worsened full‐scale intelligence quotient (FSIQ) 22,26,30,32 —when comparing KT recipients with healthy controls. We recently showed evidence of reduced FSIQ in KT recipients relative to patients who had not yet received a transplant 33 . These findings were further supported by longitudinal post‐hoc analyses which indicated change in FSIQ and nonverbal scores decreased significantly from pre‐ to post‐transplant in nine individuals 33 …”

“…In contrast, we recently showed processing speed—the ability to quickly integrate multiple types of information and utilize this input to perform a task—significantly decreased from pre‐ to post‐transplant in eight KT patients 33 . Potential persistent deficits in processing speed may be exacerbated by older age at transplant, as suggested by significantly lower processing speed scores in children transplanted at 80 months of age or greater relative to those transplanted at a younger age 33 . Similarly, cross‐sectional data indicate that executive dysfunction may continue after KT.…”

“…27,[29][30][31] We recently reported that children transplanted at an older age (≥80 months) had significantly lower FSIQ, verbal IQ, nonverbal IQ, and memory scores. 33 Medical comorbidities which are common prior to transplantation, such as anemia or dialysis modality and duration, as well as continued comorbidities associated with post-transplant care like maintenance immunosuppression may limit potential cognitive improvements following kidney transplantation.…”

“…21 In contrast, we recently showed processing speed-the ability to quickly integrate multiple types of information and utilize this input to perform a task-significantly decreased from pre-to post-transplant in eight KT patients. 33…”