Faculty Bibliography

BACKGROUND AND OBJECTIVES:Mortality from benzodiazepine/opioid interactions is a growing concern in light of the opioid epidemic. Patients on hemodialysis suffer from a high burden of physical/psychiatric conditions, which are treated with benzodiazepines, and they are three times more likely to be prescribed opioids than the general population. Therefore, we studied mortality risk associated with short- and long-acting benzodiazepines and their interaction with opioids among adults initiating hemodialysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS:The cohort of 69,368 adults initiating hemodialysis (January 2013 to December 2014) was assembled by linking US Renal Data System records to Medicare claims. Medicare claims were used to identify dispensed benzodiazepines and opioids. Using adjusted Cox proportional hazards models, we estimated the mortality risk associated with benzodiazepines (time varying) and tested whether the benzodiazepine-related mortality risk differed by opioid codispensing. RESULTS:=0.72). CONCLUSIONS:Codispensing of opioids and short-acting benzodiazepines is common among patients on dialysis, and it is associated with higher risk of death.

BACKGROUND AND OBJECTIVES:Black patients referred for kidney transplantation have surpassed many obstacles but likely face continued racial disparities before transplant. The mechanisms that underlie these disparities are unclear. We determined the contributions of socioeconomic status (SES) and comorbidities as mediators to disparities in listing and transplant. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS:=1561 white) of patients with kidney failure who were referred for and started the transplant process (2009-2018). We estimated the direct and indirect effects of SES (self-reported income, education, and employment) and medical comorbidities (self-reported and chart-abstracted) as mediators of racial disparities in listing using Cox proportional hazards analysis with inverse odds ratio weighting. Among the 983 black and 1085 white candidates actively listed, we estimated the direct and indirect effects of SES and comorbidities as mediators of racial disparities on receipt of transplant using Poisson regression with inverse odds ratio weighting. RESULTS:Within the first year, 876 (60%) black and 1028 (66%) white patients were waitlisted. The relative risk of listing for black compared with white patients was 0.76 (95% confidence interval [95% CI], 0.69 to 0.83); after adjustment for SES and comorbidity, the relative risk was 0.90 (95% CI, 0.83 to 0.97). The proportion of the racial disparity in listing was explained by SES by 36% (95% CI, 26% to 57%), comorbidity by 44% (95% CI, 35% to 61%), and SES with comorbidity by 58% (95% CI, 44% to 85%). There were 409 (42%) black and 496 (45%) white listed candidates transplanted, with a median duration of follow-up of 3.9 (interquartile range, 1.2-7.1) and 2.8 (interquartile range, 0.8-6.3) years, respectively. The incidence rate ratio for black versus white candidates was 0.87 (95% CI, 0.79 to 0.96); SES and comorbidity did not explain the racial disparity. CONCLUSIONS:SES and comorbidity partially mediated racial disparities in listing but not for transplant.

BACKGROUND:Hepatitis C virus-positive (HCV+) kidney transplant (KT) recipients are at increased risks of rejection and graft failure. The optimal induction agent for this population remains controversial, particularly regarding concerns that antithymocyte globulin (ATG) might increase HCV-related complications. METHODS:Using Scientific Registry of Transplant Recipients and Medicare claims data, we studied 6780 HCV+ and 139 681 HCV- KT recipients in 1999-2016 who received ATG or interleukin-2 receptor antagonist (IL2RA) for induction. We first examined the association of recipient HCV status with receiving ATG (versus IL2RA) using multilevel logistic regression. Then, we studied the association of ATG (versus IL2RA) with KT outcomes (rejection, graft failure, and death) and hepatic complications (liver transplant registration and cirrhosis) among HCV+ recipients using logistic and Cox regression. RESULTS:HCV+ recipients were less likely to receive ATG than HCV- recipients (living donor, adjusted odds ratio [aOR] = 0.640.770.91; deceased donor, aOR = 0.710.810.92). In contrast, HCV+ recipients who received ATG were at lower risk of acute rejection compared to those who received IL2RA (1-y crude incidence = 11.6% versus 12.6%; aOR = 0.680.820.99). There was no significant difference in the risks of graft failure (adjusted hazard ratio [aHR] = 0.861.001.17), death (aHR = 0.850.951.07), liver transplant registration (aHR = 0.580.971.61), and cirrhosis (aHR = 0.730.921.16). CONCLUSIONS:Our findings suggest that ATG, as compared to IL2RA, may lower the risk of acute rejection without increasing hepatic complications in HCV+ KT recipients. Given the higher rates of acute rejection in this population, ATG appears to be safe and reasonable for HCV+ recipients.

OBJECTIVE:To determine if the association of frailty and waitlist mortality varies by candidate age. BACKGROUND:Frailty, a construct developed in geriatrics, is a state of decreased physiologic reserve, and is associated with mortality while awaiting liver transplantation (LT). However, older candidates have high comorbidity burden and less physiologic reserve, so the relationship between frailty and waitlist mortality may vary by candidate age. METHODS:We studied adults listed for LT at 2 transplant centers. The liver frailty index (grip strength, chair stands, balance) was measured at evaluation, with frailty defined as liver frailty index  ≥ 4.5. We compared the prevalence of frailty in older (≥65 yr) and younger (18-64 yr) candidates. We studied the association between frailty, age, interaction between the 2, and waitlist mortality using competing risks regression adjusted for sex, BMI, and MELDNa. RESULTS:Among 882 LT candidates, 16.6% were ≥ 65 years. Older candidates were more likely to be frail (33.3% vs 21.7%, P = 0.002). Older age [adjusted subhazard ratio (aSHR): 2.16, 95% CI: 1.51-3.09, P < 0.001] and frailty (aSHR: 1.92, 95% CI: 1.38-2.67, P < 0.001) were independently associated with higher risk of waitlist mortality. However, the association between waitlist mortality and frailty did not vary by candidate age (aSHR of frailty for younger patients: 1.90, 95% CI: 1.28-2.80, P = 0.001; aSHR of frailty for older patients: 1.98, 95% CI: 1.07-3.67, P = 0.03; P interaction = 0.9). CONCLUSIONS:Older candidates experienced higher rates of frailty than younger candidates. However, regardless of age, frailty was associated with nearly 2-fold increased risk of waitlist mortality. Our data support the applicability of the frailty concept to the whole LT population and can guide the development of prehabilitation programs targeting frailty in LT patients of all ages.

INTRODUCTION:Multifactorial biological processes underpin dysregulation over several individual physiological systems. However, it is challenging to characterize and model this multisystemic dysregulation and its relationship with individual physiologic systems. We operationalized a theory-driven measure of multisystem dysregulation and empirically tested for measurement differences by key characteristics. METHODS:We used the Women's Health and Aging Studies (WHAS) I and II (N = 649), and the Health ABC study (N = 1515). Twelve biomarkers representing multiple systems including stress response (e.g., inflammation), endocrine system, and energy regulation were identified. A series of confirmatory factor analyses (CFA) were conducted to evaluate the interplay between physiological systems and underlying multisystem dysregulation. We evaluated convergent criterion validity of a score for multisystem dysregulation against the physical frailty phenotype, and predictive criterion validity with incidence of walking difficulty and mortality. RESULTS:A bifactor CFA, a model in which dysregulation of individual systems proceeds independently of generalized dysregulation, fit data well in WHAS (RMSEA: 0.019; CFI: 0.977; TLI: 0.961) and Health ABC (RMSEA: 0.047; CFI: 0.874; TLI: 0.787). The general dysregulation factor was associated with frailty (OR: 2.2, 95 % CI: 1.4, 3.5), and elevated risk of incident walking difficulty and mortality. Findings were replicated in Health ABC. DISCUSSION:Biomarker data from two epidemiologic studies support the construct of multisystem physiological dysregulation. Results further suggest system-specific and system-wide processes have unique and non-overlapping contributions to dysregulation in biological markers.

INTRODUCTION:"Frailty" has attracted attention for its promise of identifying vulnerable older adults, hence its potential use to better tailor geriatric health care. There remains substantial controversy, however, regarding its nature and ascertainment. Recent years have seen a proliferation of frailty assessment methods. We argue that the development of frailty assessments should be grounded in "validation"-the process of substantiating that a measurement accurately and precisely measures what it intends, identify unresolved measurement issues, and highlight measurement-related considerations for clinical practice. METHODS:Principles for validating frailty measures are elucidated. We follow principles-articulated, for example, by Borsboom-in which a construct must be clearly defined and then analyses undertaken to substantiate that a measurement accurately and precisely measures what it intends. Key elements are content validity, criterion validity, and construct validity, with an emphasis on the latter. RESULTS:We illustrate the principles for a physical frailty phenotype construct. CONCLUSIONS:Unresolved conceptual issues include the roles of intersecting concepts such as cognition, disease severity, and disability in frailty measurement, conceptualization of frailty as a state versus a continuum, and the potential need for dynamic measures and systems concepts in furthering understanding of frailty. Clinical considerations include needs to distinguish interventions designed to address frailty "symptoms" versus underlying physiology, improve "prefrailty" measures intended to screen individuals early in their frailty progression, address feasibility demands, and further visioning followed by rigorous efficacy research to address the landscape of potential uses of frailty assessment in clinical practice.

BACKGROUND:Approximately half of the patients who progress to end-stage kidney disease (ESKD) and undergo dialysis develop difficulties carrying out essential self-care activities, leading to institutionalization and mortality. It is unclear what percentage of kidney transplant (KT) candidates, a group of ESKD patients selected to be healthy enough to withstand transplantation, are functionally independent and whether independence is associated with better access to KT and reduced waitlist mortality. METHODS:We studied a prospective cohort of 3168 ESKD participants (January 2009 to June 2018) who self-reported functional independence in more basic self-care Activities of Daily Living (ADL) (needing help with eating, dressing, walking, grooming, toileting and bathing) and more complex instrumental ADL (IADL) (needing help using a phone, shopping, cooking, housework, washing, using transportation, managing medications and managing money). We estimated adjusted associations between functional independence (separately) and listing (Cox), waitlist mortality (competing risks) and transplant rates (Poisson). RESULTS:At KT evaluation, 92.4% were independent in ADLs, but only 68.5% were independent in IADLs. Functionally independent participants had a higher chance of listing for KT [ADL: adjusted hazard ratio (aHR) = 1.55, 95% confidence interval (CI) 1.30-1.87; IADL: aHR = 1.39, 95% CI 1.26-1.52]. Among KT candidates, ADL independence was associated with lower waitlist mortality risk [adjusted subdistribution HR (aSHR) = 0.66, 95% CI 0.44-0.98] and higher rate of KT [adjusted incidence rate ratio (aIRR) = 1.58, 95% CI 1.12-2.22]; the same was not observed for IADL independence (aSHR = 0.86, 95% CI 0.65-1.12; aIRR = 1.01, 95% CI 0.97-1.19). CONCLUSIONS:Functional independence in more basic self-care ADL was associated with better KT access and lower waitlist mortality. Nephrologists, geriatricians and transplant surgeons should screen KT candidates for ADLs, and identify interventions to promote independence and improve waitlist outcomes.

Understanding the economic implications of induction and maintenance immunosuppression (ISx) is important in developing personalized kidney transplant (KTx) care. Using data from a novel integrated data set including financial records from the University Health System Consortium, Medicare, and pharmacy claims (2007-2014), we estimated the differences in the impact of induction and maintenance ISx regimens on transplant hospitalization costs and Medicare payments from KTx to 3 years. Use of thymoglobulin (TMG) significantly increased transplant hospitalization costs ($12 006; P = .02), compared with alemtuzumab and basiliximab. TMG resulted in lower Medicare payments in posttransplant years 1 (-$2058; P = .05) and 2 (-$1784; P = .048). Patients on steroid-sparing ISx incurred relatively lower total Medicare spending (-$10 880; P = .01) compared with patients on triple therapy (tacrolimus, antimetabolite, and steroids). MPA/AZA-sparing, mammalian target of rapamycin inhibitors-based, and cyclosporine-based maintenance ISx regimens were associated with significantly higher payments. Alternative ISx regimens were associated with different KTx hospitalization costs and longer-term payments. Future studies of clinical efficacy should also consider cost impacts to define the economic effectiveness of alternative ISx regimens.

Frailty, a measure of physiologic reserve, is associated with poor outcomes and mortality among kidney transplant (KT) candidates and recipients. There are no national estimates of frailty in this population, which may help patient counseling and resource allocation at transplant centers. We studied 4616 KT candidates and 1763 recipients in our multicenter prospective cohort of frailty from 2008-2018 with Fried frailty measurements. Using Scientific Registry of Transplant Recipients (SRTR) data (KT candidates = 560 143 and recipients = 243 508), we projected the national prevalence of frailty (for KT candidates and recipients separately) using standardization through inverse probability weighting, accounting for candidate/recipient, donor, and transplant factors. In our multicenter cohort, 13.3% of KT candidates were frail at evaluation; 8.2% of LDKT recipients and 17.8% of DDKT recipients were frail at transplantation. Projected nationally, our modeling strategy estimated 91 738 KT candidates or 16.4% (95% confidence interval [CI] 14.4%-18.4%) of all KT candidates during the study period were frail, and that 34 822 KT recipients or 14.3% (95% CI 12.3%-16.3%) of all KT recipients were frail (LDKT = 8.2%; DDKT = 17.8%). Given the estimated national prevalence of frailty, transplant programs should consider assessing the condition during KT evaluation to improve patient counseling and resource allocation along with identification of recipients at risk for poor outcomes.