Changes in Cognitive Function After Kidney Transplantation: A Longitudinal Cohort Study.

RATIONALE & OBJECTIVE: Kidney disease negatively affects cognition. We assessed the effect of kidney transplantation (KT) on different cognitive domains. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: We examined pre- versus post-KT cognition in patients waitlisted for KT at an academic center. PREDICTORS: Transplant status. We measured cognitive function before KT (n=101), 3 months after KT (n=78), and 1 year after KT (n = 83). OUTCOMES: Our primary outcome was change in cognitive function before versus after KT. We used standard neuropsychological tests to assess global cognition (Mini-Mental State Exam [MMSE]), episodic/declarative memory (Logical Memory), psychomotor speed/visuospatial function (Digit Symbol Substitution Test [DSST], Trail Making Test [TMT] A), working memory/attention (Digit Span), executive function (TMT B), and semantic memory/verbal fluency/language (Category Fluency). ANALYTICAL APPROACH: Using linear mixed model analysis, we evaluated the changes in neuropsychological test scores adjusted for age, sex, race, education, and number of assessments. RESULTS: Before KT, Logical Memory I and II, DSST, MMSE, Category Fluency (animal naming), and Digit Span backward scores were low compared with normative values from the National Alzheimer's Coordinating Center data. Logical Memory I and II scores improved after KT (pre- vs post-KT, estimated group difference [d]=3.3, P<0.001 for Logical Memory I; d=4.27, P<0.001 for Logical Memory II), such that post-KT scores were similar to normative values (post-KT vs normative values, d = -0.37, P=0.06 for Logical Memory I; d = -0.89, P=0.08 for Logical Memory II). Category Fluency (animal naming; d=2.4, P<0.001) and DSST (d=3.12, P=0.01) scores also improved with KT, but post-KT DSST scores remained lower than normative values (post-KT vs normative values, d = -5.17, P<0.001). MMSE, Digit Span, and TMT A and B scores did not change after KT. LIMITATIONS: Single-center study. CONCLUSIONS: Episodic and verbal declarative memory normalize after KT. Semantic memory, verbal fluency, language, psychomotor speed, and visuospatial function show partial improvement. Cognitive impairment in kidney disease is therefore at least partly reversible with KT. PLAIN-LANGUAGE SUMMARY: Cognitive impairment in kidney disease affects self-esteem, vocational abilities, quality of life, health care costs, and mortality. It is not clear whether kidney transplantation (KT) improves cognition and whether the improvement is uniform across cognitive domains. The distinction between reversible and irreversible cognitive impairment has important implications in the clinical care of patients before and after KT. We assessed cognition before KT and 3 months and 12 months after KT and discovered that episodic and verbal declarative memory normalized with KT. Semantic memory, verbal fluency, language, psychomotor speed, and visuospatial function also improved with KT but did not reach normal levels. Cognitive impairment in kidney disease is therefore at least partly reversible.

Simulating and estimating agreement in the presence of multiple raters and covariates.

Cohen's and Fleiss's kappa are popular estimators for assessing agreement among two and multiple raters, respectively, for a binary response. While additional methods have been developed to account for multiple raters and covariates, they are not always applicable, rarely used, and none simplify to Cohen's kappa. Furthermore, there are no methods to simulate Bernoulli observations under the kappa agreement structure such that the developed methods could be adequately assessed. This manuscript overcomes these shortfalls. First, we developed a model-based estimator for kappa that accommodates multiple raters and covariates through a generalized linear mixed model and encompasses Cohen's kappa as a special case. Second, we created a framework to simulate dependent Bernoulli observations that upholds all 2-tuple pair of rater's kappa agreement structure and includes covariates. We used this framework to assess our method when kappa was nonzero. Simulations showed that Cohen's and Fleiss's kappa estimates were inflated unlike our model-based kappa. We analyzed an Alzheimer's disease neuroimaging study and the classic cervical cancer pathology study. The proposed model-based kappa and advancement in simulation methodology demonstrates that the popular approaches of Cohen's and Fleiss's kappa are poised to yield invalid conclusions while our work overcomes shortfalls, leading to improved inferences.

Driving Automation for Older Adults with Preclinical Alzheimer's Disease.

INTRODUCTION: Older adults with preclinical Alzheimer's disease (AD) show changes in on-road driving performance. The impact of preclinical AD on using automated vehicle (AV) technology is unknown. The aim was to evaluate safety and cognitive workload while operating AV technology in drivers with preclinical AD. INTRODUCTION: This cross-sectional study included 40 participants: 19 older adults (age 74.16 ± 4.78; MOCA scores 26.42 ± 2.52) with preclinical AD, evidenced by elevated cortical beta-amyloid; and 21 controls (age 73.81 ± 5.62; MOCA scores 28.24 ± 1.67). All participants completed two scenarios in a driving simulator. Scenario 1 included conditional automation with an emergency event that required a manual take-over maneuver. Scenario 2 was identical but with a cognitive distractor task. Emergency response time was the main safety outcome measure. Cognitive workload was calculated using moment-to-moment changes in pupillary size and converted into an Index of Cognitive Activity (ICA). Mann-Whitney U and independent t tests were used to compare group differences. RESULTS: Emergency response times were similar between drivers with preclinical AD and controls in scenario 1 (20.85 s ± 1.08 vs. 20.52 s ± 3.18; p = 0.83) and scenario 2 (14.83 s ± 7.37 vs. 13.45 s ± 10.43; p = 0.92). Likewise, no differences were found in ICA between drivers with preclinical AD and controls in scenario 1 (0.34 ± 0.08 vs. 0.33 ± 0.17; p = 0.74) or scenario 2 (0.30 ± 0.07 vs. 0.29 ± 0.17; p = 0.93). CONCLUSIONS: Older drivers with preclinical AD may safely operate AV technology, without increased response times or cognitive workload. Future on-road studies with AV technology should confirm these preliminary results in drivers with preclinical AD.

Longitudinal Changes in, and Factors Associated with, the Frequency of Condomless Sex Among People in Care for HIV Infection, HIV Outpatient Study USA, 2007-2019.

During 2007-2019, the percentage of HIV Outpatient Study participants reporting anal or vaginal condomless sex in the past 6 months ranged from a low of 17% among heterosexual males to 59% for men who have sex with men (MSM). MSM reported having had condomless sex more frequently than heterosexual males and females and were the only group in which an increase in condomless sex was observed during the study period (from 39 to 59%). Although persons with undetectable HIV viral load have effectively no risk of transmitting HIV sexually (U = U), there is still the potential risk of transmission or acquisition of other sexually transmitted infections (STIs) when engaging in condomless sex. Continuing education about risks of HIV and STI transmission as well as ongoing screening for and treatment of STIs, retention in HIV treatment, and support for sexual health are critical components of care for people living with HIV.

Normalization of Cerebral Blood Flow, Neurochemicals, and White Matter Integrity after Kidney Transplantation.

BACKGROUND: CKD is associated with abnormalities in cerebral blood flow, cerebral neurochemical concentrations, and white matter integrity. Each of these is associated with adverse clinical consequences in the non-CKD population, which may explain the high prevalence of dementia and stroke in ESKD. Because cognition improves after kidney transplantation, comparing these brain abnormalities before and after kidney transplantation may identify potential reversibility in ESKD-associated brain abnormalities. METHODS: In this study of patients with ESKD and age-matched healthy controls, we used arterial spin labeling to assess the effects of kidney transplantation on cerebral blood flow and magnetic resonance spectroscopic imaging to measure cerebral neurochemical concentrations (N-acetylaspartate, choline, glutamate, glutamine, myo-inositol, and total creatine). We also assessed white matter integrity measured by fractional anisotropy (FA) and mean diffusivity (MD) with diffusion tensor imaging. We used a linear mixed model analysis to compare longitudinal, repeated brain magnetic resonance imaging measurements before, 3 months after, and 12 months after transplantation and compared these findings with those of healthy controls. RESULTS: Study participants included 29 patients with ESKD and 19 controls; 22 patients completed post-transplant magnetic resonance imaging. Cerebral blood flow, which was higher in patients pretransplant compared with controls (P=0.003), decreased post-transplant (P<0.001) to values in controls. Concentrations of neurochemicals choline and myo-inositol that were higher pretransplant compared with controls (P=0.001 and P<0.001, respectively) also normalized post-transplant (P<0.001 and P<0.001, respectively). FA increased (P=0.001) and MD decreased (P<0.001) post-transplant. CONCLUSIONS: Certain brain abnormalities in CKD are reversible and normalize with kidney transplantation. Further studies are needed to understand the mechanisms underlying these brain abnormalities and to explore interventions to mitigate them even in patients who cannot be transplanted. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: Cognitive Impairment and Imaging Correlates in End Stage Renal Disease, NCT01883349.

Safety and target engagement profile of two oxaloacetate doses in Alzheimer's patients.

INTRODUCTION: Brain bioenergetics are defective in Alzheimer's disease (AD). Preclinical studies find oxaloacetate (OAA) enhances bioenergetics, but human safety and target engagement data are lacking. METHODS: We orally administered 500 or 1000 mg OAA, twice daily for 1 month, to AD participants (n = 15 each group) and monitored safety and tolerability. To assess brain metabolism engagement, we performed fluorodeoxyglucose positron emission tomography (FDG PET) and magnetic resonance spectroscopy before and after the intervention. We also assessed pharmacokinetics and cognitive performance. RESULTS: Both doses were safe and tolerated. Compared to the lower dose, the higher dose benefited FDG PET glucose uptake across multiple brain regions (P < .05), and the higher dose increased parietal and frontoparietal glutathione (P < .05). We did not demonstrate consistent blood level changes and cognitive scores did not improve. CONCLUSIONS: 1000 mg OAA, taken twice daily for 1 month, is safe in AD patients and engages brain energy metabolism.

A prediction-based test for multiple endpoints.

This article introduces a global hypothesis test intended for studies with multiple endpoints. Our test makes use of a priori predictions about the direction of the result of each endpoint and we weight these predictions using the sample correlation matrix. The global alternative hypothesis concerns a parameter, ϕ , defined as the researcher's ability to correctly predict the direction of each measure, essentially a binomial parameter. This allows for the test to include expected effects that are all positive, all negative or both while still using the cumulative information across those endpoints. A rejection of the null hypothesis ( H0:ϕ≤ϕ0 ) provides evidence that the researcher's underlying theory about the natural process provides a better prediction of the observed results relative to the null hypothesized predictive ability, thus indicating the theory is worthy of further study. We compare our test to O'Brien's ordinary least squares (OLS) test and show that for small samples and situations where the effect is not in the same direction across all endpoints our approach has better power, while if the effect is equidirectional across all endpoints the OLS test can have greater power.

Rates of suicidal ideation among HIV-infected patients in care in the HIV Outpatient Study 2000-2017, USA.

BACKGROUND: Suicidal ideation (SI) refers to an individual thinking about, considering or planning suicide. Identifying and characterizing persons with HIV (PWH) at greater risk for SI may lead to better suicide prevention strategies and quality of life improvement. METHODS: Using clinical data gathered from medical chart abstraction for HIV Outpatient Study (HOPS) participants from 2000 to 2017, we assessed SI frequency among PWH in care and explored factors associated with the presence of SI diagnoses using linear mixed models analyses. RESULTS: Among 6706 participants, 224 (3.3%) had a charted diagnosis of SI. Among those with SI, median age (interquartile range [IQR]) was 43.4 years [IQR: 38.7-50.3], median (IQR) CD4+ cell count was 439 cells/mm3 (IQR: 237-686), 71.4% were male, 54% were men who have sex with men (MSM), 25.4% heterosexual, and 13.4% persons who inject drugs. In multivariable analysis, persons at increased risk for SI were more likely to be: <50 years old (adjusted rate ratio [aRR] 1.86, 95% confidence interval [95%CI] 1.36-2.53), non-Hispanic/Latino black (aRR 1.75; 95%CI 1.29-2.38), have CD4+ cell count <350 cells/mm3 (aRR 1.32; 95%CI 1.05-1.65), have a viral load ≥50 copies/mL (aRR 1.49; 95%CI 1.12-1.98), have stopped antiretroviral therapy (aRR 1.46; 95%CI 1.10-1.95), have a history of: alcohol dependence (aRR 2.75; 95%CI 1.67-4.52), and drug overdose (aRR 4.09; 95%CI 2.16-7.71). CONCLUSION: Routine mental health assessment and monitoring are needed in HIV clinical practice to better understand factors associated with SI and to inform the development of preventive interventions.

Exploratory analysis of mtDNA haplogroups in two Alzheimer's longitudinal cohorts.

INTRODUCTION: Inherited mitochondrial DNA (mtDNA) variants may influence Alzheimer's disease (AD) risk. METHODS: We sequenced mtDNA from 146 AD and 265 cognitively normal (CN) subjects from the University of Kansas AD Center (KUADC) and assigned haplogroups. We further considered 244 AD and 242 CN AD Neuroimaging Initiative (ADNI) subjects with equivalent data. RESULTS: Without applying multiple comparisons corrections, KUADC haplogroup J AD and CN frequencies were 16.4% versus 7.6% (P = .007), and haplogroup K AD and CN frequencies were 4.8% versus 10.2% (P = .063). ADNI haplogroup J AD and CN frequencies were 10.7% versus 7.0% (P = .20), and haplogroup K frequencies were 4.9% versus 8.7% (P = .11). For the combined 390 AD and 507 CN cases haplogroup J frequencies were 12.8% versus 7.3% (P = .006), odds ratio (OR) = 1.87, and haplogroup K frequencies were 4.9% versus 9.5% (P = .010), OR = 0.49. Associations remained significant after adjusting for apolipoprotein E, age, and sex. CONCLUSION: This exploratory analysis suggests inherited mtDNA variants influence AD risk.

Trends for and Clinical Factors Associated with Choice of Oral P2Y12 Inhibitors for Patients on Chronic Dialysis.

BACKGROUND: Trends and clinical factors associated with prescribing choices for oral P2Y12 inhibitors (P2Y12-I) remain unknown for patients on chronic dialysis, i.e., with end-stage renal disease (ESRD). METHODS: From 2011-2014 U.S. Renal Data System registry, we identified 36,542 ESRD patients who received new prescriptions for P2Y12-I (median age 64.0 years and 54% males). Of the cohort, 93% were receiving hemodialysis and 7% on peritoneal dialysis. We analyzed trends and investigated clinical factors associated with specific P2Y12-I prescribed. RESULTS: Clopidogrel was prescribed for 95%, prasugrel for 3%, and ticagrelor for 2%. Clopidogrel was favored for those ≥75 years (18% of cohort). Compared to Caucasians, African Americans (36% of cohort) and Hispanics (19% of cohort) were less likely to receive prasugrel and ticagrelor (P<0.05). Patients receiving hemodialysis versus peritoneal dialysis were less likely to receive prasugrel over clopidogrel, adjusted odds ratio (aOR) 0.67 (0.55-0.82). Each additional year of dialysis decreased the odds of receiving prasugrel over clopidogrel, aOR 0.91 (0.85-0.98). History of atrial fibrillation reduced the odds of receiving ticagrelor or prasugrel over clopidogrel, aOR 0.69 (0.54-0.89) and 0.73 (0.60-0.89), respectively. Concomitant oral anticoagulant use was not associated with choice of P2Y12-I. Occurrence of non-ST segment elevation myocardial infarction or percutaneous coronary intervention within the 6-month period prior to the index date favored ticagrelor over prasugrel, aOR 1.31 (1.06-1.62) and 1.29 (1.01-1.66), respectively. However, prescribing trends favoring ticagrelor over prasugrel were not observed for deployment of drug-eluting, or multiple coronary stents. CONCLUSION: Between 2011 and 2014, clopidogrel remained the most common P2Y12-I whereas ticagrelor and prasugrel remained underutilized in ESRD patients. Prescribing practices for these drugs were based upon clinically approved indication for their use in the general population as well as perceived complexity of an ESRD patient including demographics, dialysis-related factors and comorbidities. Comparative effectiveness studies involving ESRD patients are needed to prove that ticagrelor and prasugrel are just as safe and effective as clopidogrel before clinicians can make informed decisions for choice of P2Y12-I in this patient population.

Erythropoietin modulation is associated with improved homing and engraftment after umbilical cord blood transplantation.

Umbilical cord blood (UCB) engraftment is in part limited by graft cell dose, generally one log less than that of bone marrow (BM)/peripheral blood (PB) cell grafts. Strategies toward increasing hematopoietic stem/progenitor cell (HSPC) homing to BM have been assessed to improve UCB engraftment. Despite recent progress, a complete understanding of how HSPC homing and engraftment are regulated is still elusive. We provide evidence that blocking erythropoietin (EPO)-EPO receptor (R) signaling promotes homing to BM and early engraftment of UCB CD34+ cells. A significant population of UCB CD34+ HSPC expresses cell surface EPOR. Exposure of UCB CD34+ HSPC to EPO inhibits their migration and enhances erythroid differentiation. This migratory inhibitory effect was reversed by depleting EPOR expression on HSPC. Moreover, systemic reduction in EPO levels by hyperbaric oxygen (HBO) used in a preclinical mouse model and in a pilot clinical trial promoted homing of transplanted UCB CD34+ HSPC to BM. Such a systemic reduction of EPO in the host enhanced myeloid differentiation and improved BM homing of UCB CD34+ cells, an effect that was overcome with exogenous EPO administration. Of clinical relevance, HBO therapy before human UCB transplantation was well-tolerated and resulted in transient reduction in EPO with encouraging engraftment rates and kinetics. Our studies indicate that systemic reduction of EPO levels in the host or blocking EPO-EPOR signaling may be an effective strategy to improve BM homing and engraftment after allogeneic UCB transplantation. This clinical trial was registered at www.ClinicalTrials.gov (#NCT02099266).

Bayesian design for two-arm randomized Phase II clinical trials with endpoints from the exponential family using multiple constraints.

Frequentist design for two-arm randomized Phase II clinical trials with outcomes from the exponential dispersion family was proposed previously, where the total sample sizes are minimized under multiple constraints on the standard errors of the estimated group means and their difference. This design was generalized from an approach specific for dichotomous outcomes. The two previous approaches measure the central tendency of each group and treatment effect based on mean and difference in means. Other measures such as median or hazard ratio are more appropriate under certain situations. In addition, the frequentist approaches assume that unknown parameters are fixed values. This does not reflect the reality that uncertainty always exists for unknowns. Compared to the frequentist methods, the Bayesian approach offers a flexible way to measure central tendency and treatment effect, and incorporate uncertainty in parameters of interest into considerations. In this article, we generalize a Bayesian design for Phase II clinical trials with endpoints in the exponential family from the two previously developed frequentist approaches. The proposed design minimizes the total sample sizes under pre-specified constraints on the expected length of posterior credible intervals for measures of treatment effect and central tendency in each group. The design is applicable for trials with fixed or optimal randomization allocation ratio and can be applied under adaptive procedure. Examples of method implementations are provided for different types of endpoints from the exponential family in both fixed and adaptive settings.

Relationship between caffeine intake and autosomal dominant polycystic kidney disease progression: a retrospective analysis using the CRISP cohort.

BACKGROUND: Caffeine has been proposed, based on in vitro cultured cell studies, to accelerate progression of autosomal dominant polycystic kidney disease (ADPKD) by increasing kidney size. Since ADPKD patients are advised to minimize caffeine intake, we investigated the effect of caffeine on disease progression in the Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease (CRISP), a prospective, observational cohort study. METHODS: Our study included 239 patients (mean age = 32.3 ± 8.9 ys; 188 caffeine consumers) with a median follow-up time of 12.5 years. Caffeine intake reported at baseline was dichotomized (any vs. none). Linear mixed models, unadjusted and adjusted for age, race, sex, BMI, smoking, hypertension, genetics and time, were used to model height-adjusted total kidney volume (htTKV) and iothalamate clearance (mGFR). Cox proportional hazards models and Kaplan-Meier plots examined the effect of caffeine on time to ESRD or death. RESULTS: Caffeine-by-time was statistically significant when modeling ln(htTKV) in unadjusted and adjusted models (p <  0.01) indicating that caffeine consumers had slightly faster kidney growth (by 0.6% per year), but htTKV remained smaller from baseline throughout the study. Caffeine consumption was not associated with a difference in mGFR, or in the time to ESRD or death (p > 0.05). Moreover the results were similar when outcomes were modeled as a function of caffeine dose. CONCLUSION: We conclude that caffeine does not have a significant detrimental effect on disease progression in ADPKD.

Prevalence and correlates of cognitive impairment in kidney transplant recipients.

BACKGROUND: There is a high prevalence of cognitive impairment in dialysis patients. The prevalence of cognitive impairment after kidney transplantation is unknown. METHODS: Study Design: Cross-sectional study. SETTING AND PARTICIPANTS: Single center study of prevalent kidney transplant recipients from a transplant clinic in a large academic center. INTERVENTION: Assessment of cognition using the Montreal Cognitive Assessment (MoCA). Demographic and clinical variables associated with cognitive impairment were also examined. Outcomes and Measurements: a) Prevalence of cognitive impairment defined by a MoCA score of <26. b) Multivariable linear and logistic regression to examine the association of demographic and clinical factors with cognitive impairment. RESULTS: Data from 226 patients were analyzed. Mean (SD) age was 54 (13.4) years, 73% were white, 60% were male, 37% had diabetes, 58% had an education level of college or above, and the mean (SD) time since kidney transplant was 3.4 (4.1) years. The prevalence of cognitive impairment was 58.0%. Multivariable linear regression demonstrated that older age, male gender and absence of diabetes were associated with lower MoCA scores (p < 0.01 for all). Estimated glomerular filtration rate (eGFR) was not associated with level of cognition. The logistic regression analysis confirmed the association of older age with cognitive impairment. CONCLUSION: Cognitive impairment is common in prevalent kidney transplant recipients, at a younger age compared to general population, and is associated with certain demographic variables, but not level of eGFR.

Cholecalciferol v. ergocalciferol for 25-hydroxyvitamin D (25(OH)D) repletion in chronic kidney disease: a randomised clinical trial.

Patients with chronic kidney disease (CKD) demonstrate complex mineral metabolism derangements and a high prevalence of vitamin D deficiency. However, the optimal method of 25-hydroxyvitamin D (25(OH)D) repletion is unknown, and trials analysing the comparative efficacy of cholecalciferol and ergocalciferol in this population are lacking. We conducted a randomised clinical trial of cholecalciferol 1250µg (50 000 IU) weekly v. ergocalciferol 1250µg (50 000 IU) weekly for 12 weeks in forty-four non-dialysis-dependent patients with stage 3-5 CKD. The primary outcome was change in total 25(OH)D from baseline to week 12 (immediately after therapy). Secondary analyses included the change in 1,25-dihydroxyvitamin D (1,25(OH)2D), parathyroid hormone (PTH), D2 and D3 sub-fractions of 25(OH)D and 1,25(OH)2D and total 25(OH)D from baseline to week 18 (6 weeks after therapy). Cholecalciferol therapy yielded a greater change in total 25(OH)D (45·0 (sd 16·5) ng/ml) v. ergocalciferol (30·7 (sd 15·3) ng/ml) from baseline to week 12 (P<0·01); this observation partially resulted from a substantial reduction in the 25(OH)D3 sub-fraction with ergocalciferol. However, following cessation of therapy, no statistical difference was observed for total 25(OH)D change from baseline to week 18 between cholecalciferol and ergocalciferol groups (22·4 (sd 12·7) v. 17·6 (sd 8·9) ng/ml, respectively; P=0·17). We observed no significant difference between these therapies with regard to changes in serum PTH or 1,25(OH)2D. Therapy with cholecalciferol, compared with ergocalciferol, is more effective at raising serum 25(OH)D in non-dialysis-dependent CKD patients while active therapy is ongoing. However, levels of 25(OH)D declined substantially in both arms following cessation of therapy, suggesting the need for maintenance therapy to sustain levels.

Effectiveness comparison of cardio-selective to non-selective ß-blockers and their association with mortality and morbidity in end-stage renal disease: a retrospective cohort study.

BACKGROUND: Within-class comparative effectiveness studies of ß-blockers have not been performed in the chronic dialysis setting. With widespread cardiac disease in these patients and potential mechanistic differences within the class, we examined whether mortality and morbidity outcomes varied between cardio-selective and non-selective ß-blockers. METHODS: Retrospective observational study of within class ß-blocker exposure among a national cohort of new chronic dialysis patients (N = 52,922) with hypertension and dual eligibility (Medicare-Medicaid). New ß-blocker users were classified according to their exclusive use of one of the subclasses. Outcomes were all-cause mortality (ACM) and cardiovascular morbidity and mortality (CVMM). The associations of cardio-selective and non-selective agents on outcomes were adjusted for baseline characteristics using Cox proportional hazards. RESULTS: There were 4938 new ß-blocker users included in the ACM model and 4537 in the CVMM model: 77 % on cardio-selective ß-blockers. Exposure to cardio-selective and non-selective agents during the follow-up period was comparable, as measured by proportion of days covered (0.56 vs. 0.53 in the ACM model; 0.56 vs 0.54 in the CVMM model). Use of cardio-selective ß-blockers was associated with lower risk for mortality (AHR = 0.84; 99 % CI = 0.72-0.97, p = 0.0026) and lower risk for CVMM events (AHR = 0.86; 99 % CI = 0.75-0.99, p = 0.0042). CONCLUSION: Among new ß-blockers users on chronic dialysis, cardio-selective agents were associated with a statistically significant 16 % reduction in mortality and 14 % in cardiovascular morbidity and mortality relative to non-selective ß-blocker users. A randomized clinical trial would be appropriate to more definitively answer whether cardio-selective ß-blockers are superior to non-selective ß-blockers in the setting of chronic dialysis.

Comparative Effectiveness of Renin-Angiotensin System Antagonists in Maintenance Dialysis Patients.

BACKGROUND/AIMS: Whether angiotensin converting enzyme inhibitors (ACE) and angiotensin receptor blockers (ARB) are differentially associated with reductions in cardiovascular events and mortality in patients receiving maintenance dialysis is uncertain. We compared outcomes between ACE and ARB users among hypertensive, maintenance dialysis patients. METHODS: National retrospective cohort study of hypertensive, Medicare-Medicaid eligible patients initiating chronic dialysis between 1/1/2000 to 12/31/2005. The exposure of interest was new use of either an ACEI or ARB. Outcomes were all-cause mortality (ACM) and combined cardiovascular hospitalization or death (CV-endpoint). Cox proportion hazards models were used to compare the effect of ACEI vs ARB use on ACM and, separately, CV-endpoint. RESULTS: ACM models were based on 3,555 ACEI and 1,442 ARB new users, while CV-endpoint models included 3,289 ACEI and 1,346 ARB new users. After statistical adjustments, ACEI users had higher hazard ratios for ACM (AHR = 1.22, 99% CI 1.05-1.42) and CV-endpoint (AHR = 1.12, 99% CI 0.99-1.27). CONCLUSIONS: Patients initiating maintenance dialysis who received an ACEI faced an increased risk for mortality and a trend towards an increased risk for CV-endpoints when compared to patients who received an ARB. Validation of these results in a rigorous clinical trial is warranted.

Association of multiple ischemic strokes with mortality in incident hemodialysis patients: an application of multistate model to determine transition probabilities in a retrospective observational cohort.

BACKGROUND: Little is known about the effect of multiple, or subsequent, ischemic strokes in patients receiving hemodialysis. METHODS: We undertook a retrospective cohort study of incident hemodialysis patients with Medicare coverage who had experienced a first ischemic stroke. Factors associated with either a subsequent ischemic stroke or death following a first new stroke were modeled. A multistate model with Cox proportional hazards was used to predict transition probabilities from first ischemic stroke to either subsequent stroke or to death, and the demographic and clinical factors associated with the respective transition probabilities were determined. Effect of a subsequent ischemic stroke on survival was quantified. RESULTS: Overall, 12,054 individuals (mean age 69.7 years, 41.3 % male, 53.0 % Caucasian and 34.0 % African-American) experienced a first new ischemic stroke. Female sex was associated with an increased risk of having a subsequent ischemic stroke (adjusted hazard ratio 1.37, 95 % confidence intervals 1.20 - 1.56, P < 0.0001); African-Americans, as compared to Caucasians, had lower likelihood of dying after a first new ischemic stroke (0.81, 0.77 - 0.85, P < 0.0001). A subsequent stroke trended towards having a higher likelihood of transitioning to death compared to a first new ischemic stroke on dialysis (1.72, 0.96 - 3.09, P = 0.071). When a subsequent ischemic stroke occurs at 24 months, probability of survival dropped >15 %, in absolute terms, from 0.254 to 0.096, with substantial drops observed at subsequent time points such that the probability of survival was more than halved. CONCLUSIONS: Likelihood of subsequent ischemic stroke and of survival in hemodialysis patients appears to vary by sex and race: females are more likely than males to experience a subsequent ischemic stroke, and Caucasians are more likely than African-Americans to die after a first new ischemic stroke. The risk of a transitioning to a subsequent stroke (after having had a first) increases until about 1 year, then decreases. Subsequent strokes are associated with decreased probability of survival, an effect which increases as time since first stroke elapses. This information may be of assistance to clinicians when counseling hemodialysis patients about the implications of recurrent ischemic stroke.

Restoration of function after brain damage using a neural prosthesis.

Neural interface systems are becoming increasingly more feasible for brain repair strategies. This paper tests the hypothesis that recovery after brain injury can be facilitated by a neural prosthesis serving as a communication link between distant locations in the cerebral cortex. The primary motor area in the cerebral cortex was injured in a rat model of focal brain injury, disrupting communication between motor and somatosensory areas and resulting in impaired reaching and grasping abilities. After implantation of microelectrodes in cerebral cortex, a neural prosthesis discriminated action potentials (spikes) in premotor cortex that triggered electrical stimulation in somatosensory cortex continuously over subsequent weeks. Within 1 wk, while receiving spike-triggered stimulation, rats showed substantially improved reaching and grasping functions that were indistinguishable from prelesion levels by 2 wk. Post hoc analysis of the spikes evoked by the stimulation provides compelling evidence that the neural prosthesis enhanced functional connectivity between the two target areas. This proof-of-concept study demonstrates that neural interface systems can be used effectively to bridge damaged neural pathways functionally and promote recovery after brain injury.