Delirium, changes in cognitive function, and risk of diagnosed dementia after kidney transplantation

Age Is Just a Number for Older Kidney Transplant Patients

The rise in the mean age of the global population has led to an increase in older kidney transplant (KT) patients. This demographic shift, coupled with the ongoing organ shortage, requires a nuanced understanding of which older adults are most suitable for KT. Recognizing the increased heterogeneity among older adults and the limitations of solely relying on chronological age, there is a need to explore alternative aging metrics beyond chronological age. In this review, we discuss the impact of older age on access to KT and postoperative outcomes. Emphasizing the need for a comprehensive evaluation that extends beyond chronological age, we explore alternative aging metrics such as frailty, sarcopenia, and cognitive function, underscoring their potential role in enhancing the KT evaluation process. Most importantly, we aim to contribute to the ongoing discourse, fostering an optimized approach to KT for the rapidly growing population of older adults.

Neighborhood Racial and Ethnic Segregation and the Risk of Dementia in Older Adults Living with Kidney Failure

Key Points

Background

Dementia disproportionately affects older minoritized adults with kidney failure. To better understand the mechanism of this disparity, we studied the role of racial and ethnic segregation (segregation hereafter), i.e., a form of structural racism recently identified as a mechanism in numerous other health disparities.

Methods

We identified 901,065 older adults (aged ≥55 years) with kidney failure from 2003 to 2019 using the United States Renal Data System. We quantified dementia risk across tertiles of residential neighborhood segregation score using cause-specific hazard models, adjusting for individual- and neighborhood-level factors. We included an interaction term to quantify the differential effect of segregation on dementia diagnosis by race and ethnicity.

Results

We identified 79,851 older adults with kidney failure diagnosed with dementia between 2003 and 2019 (median follow-up: 2.2 years). Compared with those in low-segregation neighborhoods, older adults with kidney failure in high-segregation neighborhoods had a 1.63-fold (95% confidence interval [CI], 1.60 to 1.66) higher risk of dementia diagnosis, an association that differed by race and ethnicity (Asian: adjusted hazard ratio [aHR] = 1.26, 95% CI, 1.15 to 1.38; Black: aHR = 1.66, 95% CI, 1.61 to 1.71; Hispanic: aHR = 2.05, 95% CI, 1.93 to 2.18; White: aHR = 1.59, 95% CI, 1.55 to 1.64; P interaction < 0.001). Notably, older Asian (aHR = 1.76; 95% CI, 1.64 to 1.89), Black (aHR = 2.65; 95% CI, 2.54 to 2.77), Hispanic (aHR = 2.15; 95% CI, 2.04 to 2.26), and White (aHR = 2.20; 95% CI, 2.09 to 2.31) adults with kidney failure residing in minority-predominant high-segregation neighborhoods had a higher risk of dementia diagnosis compared with older White adults with kidney failure in White-predominant high-segregation neighborhoods. Moreover, older adults with kidney failure receiving care at dialysis facilities located in high-segregation neighborhoods also experienced a higher risk of dementia diagnosis (aHR = 1.53; 95% CI, 1.50 to 1.56); this association differed by race and ethnicity (P interaction < 0.001).

Conclusions

Residing in or receiving care at dialysis facilities located in high-segregation neighborhoods was associated with a higher risk of dementia diagnosis among older individuals with kidney failure, particularly minoritized individuals.

Association of Postoperative Delirium With Incident Dementia and Graft Outcomes Among Kidney Transplant Recipients

BACKGROUND

Kidney transplant (KT) recipients have numerous risk factors for delirium, including those shared with the general surgical population (eg, age and major surgery) and transplant-specific factors (eg, neurotoxic immunosuppression medications). Evidence has linked delirium to long-term dementia risk in older adults undergoing major surgery. We sought to characterize dementia risk associated with post-KT delirium.

METHODS

Using the United States Renal Data System datasets, we identified 35 800 adult first-time KT recipients ≥55 y. We evaluated risk factors for delirium using logistic regression. We evaluated the association between delirium and incident dementia (overall and by subtype: Alzheimer's, vascular, and other/mixed-type), graft loss, and death using Fine and Gray's subhazards models and Cox regression.

RESULTS

During the KT hospitalization, 0.9% of recipients were diagnosed with delirium. Delirium risk factors included age (OR = 1.40, 95% CI, 1.28-1.52) and diabetes (OR = 1.38, 95% CI, 1.10-1.73). Delirium was associated with higher risk of death-censored graft loss (aHR = 1.52, 95% CI, 1.12-2.05) and all-cause mortality (aHR = 1.53, 95% CI, 1.25-1.89) at 5 y post-KT. Delirium was also associated with higher risk of dementia (adjusted subhazard ratio [aSHR] = 4.59, 95% CI, 3.48-6.06), particularly vascular dementia (aSHR = 2.51, 95% CI, 1.01-6.25) and other/mixed-type dementia (aSHR = 5.58, 95% CI, 4.24-7.62) subtypes. The risk of all-type dementia associated with delirium was higher for younger recipients aged between 55 and 64 y ( Pinteraction  = 0.01).

CONCLUSIONS

Delirium is a strong risk factor for subsequent diagnosis of dementia among KT recipients, particularly those aged between 55 and 64 y at the time of transplant. Patients experiencing posttransplant delirium might benefit from early interventions to enhance cognitive health and surveillance for cognitive impairment to enable early referral for dementia care.

COVID-19 and Access to Kidney Transplantation for Older Candidates in the United States: A National Registry Study

Rationale & Objective

Coronavirus disease (COVID)-19 has likely impacted accessibility to transplantation services among older adults (age ≥65 years). We quantified the impact of COVID-19 on kidney transplantation access for older kidney-only candidates registered on the United States (US) kidney waitlist.

Study Design

Retrospective analysis of registry data.

Setting & Participants

57,222 older adults who were part of or added to the US kidney waitlist between January 1, 2016 and February 28, 2022, identified using the Scientific Registry of Transplant Recipients (SRTR).

Exposures

Four COVID-19 waves and one nonwave period based on the national incidence of COVID-19 in the US (initial: March 15-May 30, 2020; winter 2020-2021: December 1, 2020-January 31, 2021; delta: August 1, 2021-September 30, 2021; omicron: December 1, 2021-February 28, 2022; nonwave: inter-wave periods).

Outcomes

Waitlist registrations, deceased-donor kidney transplants, living-donor kidney transplants, waitlist mortality, and waitlist removals due to deteriorating condition (hereafter referred to as removals).

Analytical Approach

Poisson regression for the adjusted incidence rate ratio (aIRR) of each outcome during the COVID-19 waves and the nonwave period relative to reference (January 1, 2016-December 31, 2019), adjusted for seasonality and secular trends.

Results

Waitlist registrations initially declined and increased henceforth. Deceased-donor kidney transplants and living-donor kidney transplants remained below-expected levels during all waves. Waitlist mortality peaked during the winter 2020-2021 wave (aIRR: 1.701.982.30) and has declined since; mortality rates were 139%, 107%, and 251% above expected for Black candidates, men, and candidates aged ≥75 years, respectively, during the winter 2020-2021 wave. Removals increased from 22% below expected levels (initial wave) to 26% above expected levels (omicron wave); removals were nonsignificantly higher than expected during the omicron wave for older Black and Hispanic candidates.

Limitations

The findings are not generalizable to those listed at earlier ages with prolonged waitlist times. Additionally, using national COVID-19 incidence does not consider local policy and health care variations. Lastly, aIRRs must be interpreted cautiously due to smaller daily event counts.

Conclusions

COVID-19 was associated with fewer transplants and increased mortality and removals in older kidney transplant candidates. Transplant providers should consider this impact and implement policies and practices to ensure the continuity of care.

Plain-Language Summary

The proportion of older adults on the kidney transplant waitlist is increasing, but the impact of COVID-19 on this population is not well characterized. In this study, we looked at incident waitlist registrations, deceased- and living-donor kidney transplants, and waitlist mortality and removals due to deteriorating condition over 4 waves of COVID-19. We found that transplantation services did not fully recover to prepandemic levels as of March 2022. Notably, racial/ethnic minorities and older men experienced lower rates of kidney transplants and higher rates of waitlist mortality, respectively, relative to White candidates and older women. Identifying vulnerable subpopulations affected by COVID-19 and its long-term impact is crucial for creating strategies to ensure the continuity of care in this population during public health emergencies.

Secondary Hyperparathyroidism and Cognitive Decline

Purpose of Review

Secondary hyperparathyroidism (SHPT) likely contributes to the high prevalence of cognitive decline found among individuals with end-stage kidney disease (ESKD). Our objective is to critically evaluate the recent literature regarding the association between SHPT and cognitive decline and identify potential mechanisms.

Recent Findings

Nine studies assessing the relationship between SHPT and cognition have been published in the last two decades, each showing that elevated parathyroid hormone (PTH) levels were associated with cognitive decline. One also found structural changes within the brain related to SHPT. Additionally, two found that SHPT treatment decreases the risk of cognitive decline in ESKD patients.

Summary

SHPT is associated with cognitive impairment. However, the severity of SHPT associated with these changes and the specific cognitive domains affected remain unclear. Future studies are needed to focus on specific cognitive domains, the trajectory of cognitive decline, and optimal treatment strategies including the impact of kidney transplant and tertiary hyperparathyroidism.