A high-glycemic diet is associated with cerebral amyloid burden in cognitively normal older adults

Background: Little is known about the relation between dietary intake and cerebral amyloid accumulation in aging.Objective: We assessed the association of dietary glycemic measures with cerebral amyloid burden and cognitive performance in cognitively normal older adults.Design: We performed cross-sectional analyses relating dietary glycemic measures [adherence to a high-glycemic-load diet (HGLDiet) pattern, intakes of sugar and carbohydrates, and glycemic load] with cerebral amyloid burden (measured by florbetapir F-18 positron emission tomography) and cognitive performance in 128 cognitively normal older adults who provided eligibility screening data for the University of Kansas's Alzheimer's Prevention through Exercise (APEX) Study. The study began in November 2013 and is currently ongoing.Results: Amyloid was elevated in 26% (n = 33) of participants. HGLDiet pattern adherence (P = 0.01), sugar intake (P = 0.03), and carbohydrate intake (P = 0.05) were significantly higher in participants with elevated amyloid burden. The HGLDiet pattern was positively associated with amyloid burden both globally and in all regions of interest independently of age, sex, and education (all P ≤ 0.001). Individual dietary glycemic measures (sugar intake, carbohydrate intake, and glycemic load) were also positively associated with global amyloid load and nearly all regions of interest independently of age, sex, and educational level (P ≤ 0.05). Cognitive performance was associated only with daily sugar intake, with higher sugar consumption associated with poorer global cognitive performance (global composite measure and Mini-Mental State Examination) and performance on subtests of Digit Symbol, Trail Making Test B, and Block Design, controlling for age, sex, and education.Conclusion: A high-glycemic diet was associated with greater cerebral amyloid burden, which suggests diet as a potential modifiable behavior for cerebral amyloid accumulation and subsequent Alzheimer disease risk. This trial was registered at clinicaltrials.gov as NCT02000583.

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.

Discrepancies between Perceived and Measured Cognition in Kidney Transplant Recipients: Implications for Clinical Management

BACKGROUND

Cognitive impairment is common in kidney transplant (KT) recipients and affects quality of life, graft survival, morbidity, and mortality. Failure to identify patients with cognitive impairment can withhold appropriate and timely intervention. This study determines whether measured cognition with standard screening tools offers any advantage over perceived cognition in screening transplant patients for cognitive impairment.

METHODS

Cognition was assessed in 157 KT recipients using the Montreal Cognitive Assessment (MoCA; measured cognition). In addition, transplant physicians and nurse coordinators were asked to rate transplant recipients' level of cognition after routine clinical interactions (perceived cognition). Physicians and nurses were blind to MoCA scores. Perceived cognition scores were compared to MoCA scores.

RESULTS

Perceived cognition scores fairly correlated with MOCA scores (γ = 0.24, p = 0.001 for physicians and γ = 0.33, p < 0.0001 for nurses). Physician scores moderately correlated with nurses scores (κ = 0.44, p < 0.0001). Clinical perception had a low accuracy for identifying patients with cognitive impairment (sensitivity 66% for physicians, 65% for nurses), and those without cognitive impairment (specificity 67% for physicians, 76% for nurses).

CONCLUSION

Clinical perception is inaccurate at detecting cognitive impairment in KT recipients. Objective tests should be considered to screen KT recipients for cognitive impairment.

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.

Aerobic exercise for Alzheimer's disease: A randomized controlled pilot trial

BACKGROUND

There is increasing interest in the role of physical exercise as a therapeutic strategy for individuals with Alzheimer's disease (AD). We assessed the effect of 26 weeks (6 months) of a supervised aerobic exercise program on memory, executive function, functional ability and depression in early AD.

METHODS AND FINDINGS

This study was a 26-week randomized controlled trial comparing the effects of 150 minutes per week of aerobic exercise vs. non-aerobic stretching and toning control intervention in individuals with early AD. A total of 76 well-characterized older adults with probable AD (mean age 72.9 [7.7]) were enrolled and 68 participants completed the study. Exercise was conducted with supervision and monitoring by trained exercise specialists. Neuropsychological tests and surveys were conducted at baseline,13, and 26 weeks to assess memory and executive function composite scores, functional ability (Disability Assessment for Dementia), and depressive symptoms (Cornell Scale for Depression in Dementia). Cardiorespiratory fitness testing and brain MRI was performed at baseline and 26 weeks. Aerobic exercise was associated with a modest gain in functional ability (Disability Assessment for Dementia) compared to individuals in the ST group (X2 = 8.2, p = 0.02). There was no clear effect of intervention on other primary outcome measures of Memory, Executive Function, or depressive symptoms. However, secondary analyses revealed that change in cardiorespiratory fitness was positively correlated with change in memory performance and bilateral hippocampal volume.

CONCLUSIONS

Aerobic exercise in early AD is associated with benefits in functional ability. Exercise-related gains in cardiorespiratory fitness were associated with improved memory performance and reduced hippocampal atrophy, suggesting cardiorespiratory fitness gains may be important in driving brain benefits.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01128361.

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.

Generalized optimal design for two-arm, randomized phase II clinical trials with endpoints from the exponential dispersion family

For two-arm randomized phase II clinical trials, previous literature proposed an optimal design that minimizes the total sample sizes subject to multiple constraints on the standard errors of the estimated event rates and their difference. The original design is limited to trials with dichotomous endpoints. This paper extends the original approach to be applicable to phase II clinical trials with endpoints from the exponential dispersion family distributions. The proposed optimal design minimizes the total sample sizes needed to provide estimates of population means of both arms and their difference with pre-specified precision. Its applications on data from specific distribution families are discussed under multiple design considerations. Copyright © 2016 John Wiley & Sons, Ltd.

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

Background

Within-class comparative effectiveness studies of β-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 β-blockers.

Methods

Retrospective observational study of within class β-blocker exposure among a national cohort of new chronic dialysis patients (N = 52,922) with hypertension and dual eligibility (Medicare-Medicaid). New β-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 β-blocker users included in the ACM model and 4537 in the CVMM model: 77 % on cardio-selective β-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 β-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 β-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 β-blocker users. A randomized clinical trial would be appropriate to more definitively answer whether cardio-selective β-blockers are superior to non-selective β-blockers in the setting of chronic dialysis.

Open-source, Rapid Reporting of Dementia Evaluations

The National Institutes of Health Alzheimer's Disease Center consortium requires member institutions to build and maintain a longitudinally characterized cohort with a uniform standard data set. Increasingly, centers are employing electronic data capture to acquire data at annual evaluations. In this paper, the University of Kansas Alzheimer's Disease Center reports on an open-source system of electronic data collection and reporting to improve efficiency. This Center capitalizes on the speed, flexibility and accessibility of the system to enhance the evaluation process while rapidly transferring data to the National Alzheimer's Coordinating Center. This framework holds promise for other consortia that regularly use and manage large, standardized datasets.

The Effect of Model Fidelity on Learning Outcomes of a Simulation-Based Education Program for Central Venous Catheter Insertion

INTRODUCTION

Simulation-based education for central venous catheter (CVC) insertion has been repeatedly documented to improve performance, but the impact of simulation model fidelity has not been described. The aim of this study was to examine the impact of the physical fidelity of the simulation model on learning outcomes for a simulation-based education program for CVC insertion.

METHODS

Forty consecutive residents rotating through the medical intensive care unit of an academic medical center completed a simulation-based education program for CVC insertion. The curriculum was designed in accordance with the principles of deliberate practice and mastery learning. Each resident underwent baseline skills testing and was then randomized to training on a commercially available CVC model with high physical fidelity (High-Fi group) or a simply constructed model with low physical fidelity (Low-Fi group) in a noninferiority trial. Upon completion of their medical intensive care unit rotation 4 weeks later, residents returned for repeat skills testing on the high-fidelity model using a 26-item checklist.

RESULTS

The mean (SD) posttraining score on the 26-item checklist for the Low-Fi group was 23.8 (2.2) (91.5%) and was not inferior to the mean (SD) score for the High-Fi group of 22.5 (2.6) (86.5%) (P < 0.0001). Residents in both groups judged the training program to be highly useful despite perceiving a lesser degree of physical realism in the low-fidelity model compared with the high-fidelity model (P = 0.05).

CONCLUSIONS

Simulation-based education using equipment with low physical fidelity can achieve learning outcomes comparable with those with high-fidelity equipment, as long as other aspects of fidelity are maintained and robust educational principles are applied during the design of the curriculum.

Modeling Percentile Rank of Cardiorespiratory Fitness Across the Lifespan

PURPOSE

The purpose of this investigation was to create an equation for continuous percentile rank of maximal oxygen consumption (VO₂ max) from ages 20 to 99.

METHODS

We used a two-staged modeling approach with existing normative data from the American College of Sports Medicine for VO₂ max. First, we estimated intercept and slope parameters for each decade of life as a logistic function. We then modeled change in intercept and slope as functions of age (stage two) using weighted least squares regression. The resulting equations were used to predict fitness percentile rank based on age, sex, and VO₂ max, and included estimates for individuals beyond 79 years old.

RESULTS

We created a continuous, sex specific model of VO₂ max percentile rank across the lifespan.

CONCLUSIONS

Percentile ranking of VO₂ max can be made continuous and account for adults aged 20 to 99 with reasonable accuracy, improving the utility of this normalization procedure in practical and research settings, particularly in aging populations.

An ensemble survival model for estimating relative residual longevity following stroke: Application to mortality data in the chronic dialysis population

Time-dependent covariates can be modeled within the Cox regression framework and can allow both proportional and nonproportional hazards for the risk factor of research interest. However, in many areas of health services research, interest centers on being able to estimate residual longevity after the occurrence of a particular event such as stroke. The survival trajectory of patients experiencing a stroke can be potentially influenced by stroke type (hemorrhagic or ischemic), time of the stroke (relative to time zero), time since the stroke occurred, or a combination of these factors. In such situations, researchers are more interested in estimating lifetime lost due to stroke rather than merely estimating the relative hazard due to stroke. To achieve this, we propose an ensemble approach using the generalized gamma distribution by means of a semi-Markov type model with an additive hazards extension. Our modeling framework allows stroke as a time-dependent covariate to affect all three parameters (location, scale, and shape) of the generalized gamma distribution. Using the concept of relative times, we answer the research question by estimating residual life lost due to ischemic and hemorrhagic stroke in the chronic dialysis population.

The characterization of a base-width neutral step as the first step for balance recovery in moderate Parkinson's disease

PURPOSE

The purpose of this study is to characterize the base-width neutral step (BNS) as the first step in a compensatory step response in persons with moderate Parkinson's disease (PD), and its effect on balance recovery.

MATERIALS AND METHODS

Ten PD and 10 healthy controls (HCs) responded to a posterior waist pull. A BNS was defined if the first step was less than 50 mm. The length, height, duration and velocity of the BNS and its effect on balance recovery time and center of mass location at recovery were compared to the first step within other stepping strategies (single step (SS), multiple step (MS)). A linear mixed model was used to compare across strategies.

RESULTS

Six of ten persons with PD compared to zero HC used a BNS. The BNS was shorter in length and duration compared to MS responses in HC, and shorter in duration compared to MS responses in PD. The BNS was slower in velocity compared to every other strategy. BNS use resulted in a longer recovery time compared to all strategies in HC and SS responses in PD, and trended toward a longer recovery time compared to MS responses in PD.

CONCLUSIONS

The BNS as the first step in a MS response may be an unreported strategy for compensatory stepping in PD. This study suggests that the cost of utilizing the BNS may be a longer time for recovery, but further work is necessary to understand the progression of the BNS as PD severity increases.

Relationship between calcium channel blocker class and mortality in dialysis

BACKGROUND AND OBJECTIVE

The comparative effectiveness of dihydropyridine (DHP) and non-DHP calcium channel blockers (CCBs) in maintenance dialysis patients has not been well-studied.

METHODS

A retrospective cohort of hypertensive patients initiating dialysis was created. New CCB initiators, defined as individual who had no evidence of CCB use in the first 90 days of dialysis but who were initiated by day 180, were followed from their first day of medication exposure until event or censoring; events consisted of all-cause mortality (ACM) and a combined endpoint of cardiovascular morbidity or mortality (CVMM). Cox proportional hazards models were used to determine adjusted hazard ratios (AHRs) comparing the effect of DHPs vs. non-DHPs.

RESULTS

There were 2900 and 2704 new initiators of CCBs in the ACM and CVMM models, respectively. Adjusted for other factors, use of DHPs, compared to non-DHPs, was associated with an AHR of 0.77 (99% confidence intervals, 0.64 - 0.93, P = 0.0004) for ACM and 0.86 (0.72 - 1.02, P = 0.024) for CVMM. Results were similar when individuals who initiated therapy at any point after the cohort inception were included, with AHRs of 0.60 (0.53 - 0.69, P < 0.0001) and 0.77 (0.67 - 0.89, P < 0.0001) for ACM and CVMM, respectively. Further, elimination of individuals with chronic atrial fibrillation resulted in AHRs of 0.71 and 0.70 for ACM and CVVM, respectively.

CONCLUSION

DHPs, as compared to non-DHPs, were associated with reduced hazard of death or cardiovascular morbidity and mortality; potential mechanisms of action require further study.

Evaluating Variables as Unbiased Proxies for Other Measures: Assessing the Step Test Exercise Prescription as a Proxy for the Maximal, High-intensity Peak Oxygen Consumption in Older Adults

To assess validity of a low-intensity measure of fitness (X) in a population of older adults as a proxy measure for the original, high-intensity measure (Y), we used ordinary least square regression with the new, potential proxy measure (X) as the sole explanatory variable for Y. A perfect proxy measure would be unbiased (i.e., result in a regression line with a y-intercept of zero and a slope of one) with no error (variance equal to zero). We evaluated the properties of potential biases of proxy measures. A two degree-of-freedom approach using a contrast matrix in the setting of simple linear ordinary least squares regression was compared to a one degree-of-freedom paired t test alternative approach. We found that substantial improvements in power could be gained through use of the two degree-of-freedom approach in many settings, while scenarios where no linear bias was present there could be modest gains from the paired t test approach. In general, the advantages of the two degree-of-freedom approach outweighed the benefits of the one degree-of-freedom approach. Using the two degree-of-freedom approach, we assessed the data from our motivating example and found that the low-intensity fitness measure was biased, and thus was not a good proxy for the original, high-intensity measure of fitness in older adults.

The dynamic association of body mass index and all-cause mortality in multiple cohorts and its impacts

Background

In the literature, different shapes of associations have been found between body mass index (BMI) and mortality and some of the findings were opposite to each other. The association of BMI and mortality in a single cohort has been found to be dynamic that can lead to different findings under different settings. The identified dynamic features were consistent with the heterogeneity in the literature. It is meaningful to find out whether such dynamic associations exist in other populations.

Methods

Data of six different cohorts were used for analysis and comparison. The proportional hazards assumptions for BMI in Cox models were tested to identify dynamic associations in each cohort. Time-dependent covariates Cox model was used to model the association of BMI and mortality risk as functions of follow-up time. The Cox model was applied to the pooled data with survival times censored at 5 to 40 years to show the potential impact of the dynamic association on traditional Meta-analysis.

Results and discussion

Dynamic associations were identified in six models (4 for men and 2 for women), four of which showed the same changing pattern: the elevated mortality risk for low BMI decreased while that for high BMI increased with follow-up time. When the Cox model was applied to the pooled data excluding the largest and also the shortest cohort, low BMI was but high BMI was not associated with high mortality for men with censoring at 5 years but the association for low BMI became weaker and that for high BMI became much stronger when censoring time was at 40 years. The dynamic association indicated that shorter studies tend to obtain inverse associations between BMI and mortality while longer studies tend to obtain J-shaped associations.

Conclusions

Different or even opposite results about body weight and mortality in the literature may be in part due to the underlying dynamic association of BMI and mortality. The dynamic features need to be taken into consideration in future studies.

Relationship between stroke and mortality in dialysis patients

BACKGROUND AND OBJECTIVES

Stroke is common in patients undergoing long-term dialysis, but the implications for mortality after stroke in these patients are not fully understood.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A large cohort of dually-eligible (Medicare and Medicaid) patients initiating dialysis from 2000 to 2005 and surviving the first 90 days was constructed. Medicare claims were used to ascertain ischemic and hemorrhagic strokes occurring after 90-day survival. A semi-Markov model with additive hazard extension was generated to estimate the association between stroke and mortality, to calculate years of life lost after a stroke, and to determine whether race was associated with differential survival after stroke.

RESULTS

The cohort consisted of 69,371 individuals representing >112,000 person-years of follow-up. Mean age±SD was 60.8±15.5 years. There were 21.1 (99% confidence interval [99% CI], 20.0 to 22.3) ischemic strokes and 4.7 (99% CI, 4.2 to 5.3) hemorrhagic strokes after cohort entry per 1000 patient-years. At 30 days, mortality was 17.9% for ischemic stroke and 53.4% for hemorrhagic stroke. The adjusted hazard ratio (AHR) depended on time since entry into the cohort; for patients who experienced a stroke at 1 year after cohort entry, for example, the AHR of hemorrhagic stroke for mortality was 25.4 (99% CI, 22.4 to 28.4) at 1 week, 9.9 (99% CI, 8.4 to 11.6) at 3 months, 5.9 (99% CI, 5.0 to 7.0) at 6 months, and 1.8 (99% CI, 1.5 to 2.1) at 24 months. The corresponding AHRs for ischemic stroke were 11.7 (99% CI, 10.2 to 13.1) at 1 week, 6.6 (99% CI, 6.4 to 6.7) at 3 months, and 4.7 (99% CI, 4.5 to 4.9) at 6 months, remaining significantly >1.0 even at 48 months. Median months of life lost were 40.7 for hemorrhagic stroke and 34.6 for ischemic stroke. For both stroke types, mortality did not differ by race.

CONCLUSIONS

Dialysis recipients have high mortality after a stroke with corresponding decrements in remaining years of life. Poststroke mortality does not differ by race.

Estimation of Drug Effectiveness by Modeling Three Time-dependent Covariates: An Application to Data on Cardioprotective Medications in the Chronic Dialysis Population

In a population of chronic dialysis patients with an extensive burden of cardiovascular disease, estimation of the effectiveness of cardioprotective medication in literature is based on calculation of a hazard ratio comparing hazard of mortality for two groups (with or without drug exposure) measured at a single point in time or through the cumulative metric of proportion of days covered (PDC) on medication. Though both approaches can be modeled in a time-dependent manner using a Cox regression model, we propose a more complete time-dependent metric for evaluating cardioprotective medication efficacy. We consider that drug effectiveness is potentially the result of interactions between three time-dependent covariate measures, current drug usage status (ON versus OFF), proportion of cumulative exposure to drug at a given point in time, and the patient's switching behavior between taking and not taking the medication. We show that modeling of all three of these time-dependent measures illustrates more clearly how varying patterns of drug exposure affect drug effectiveness, which could remain obscured when modeled by the more standard single time-dependent covariate approaches. We propose that understanding the nature and directionality of these interactions will help the biopharmaceutical industry in better estimating drug efficacy.

Antihypertensive medication exposure and cardiovascular outcomes in hemodialysis patients

BACKGROUND/AIMS

Our understanding of the effectiveness of cardioprotective medications in maintenance dialysis patients is based upon drug exposures assessed at a single point in time. We employed a novel, time-dependent approach to modeling medication use over time to examine outcomes in a large national cohort.

METHODS

We linked Medicaid prescription claims with United States Renal Data System registry data and Medicare claims for 52,922 hypertensive maintenance dialysis patients. All-cause mortality and a combined cardiovascular disease (CVD)-endpoint were modeled as functions of exposure to cardioprotective antihypertensive medications (renin angiotensin system antagonists, β-adrenergic blockers, and calcium channel blockers) measured with three time-dependent covariates (weekly exposure status, proportion of prior weeks with exposure, and number of switches in exposure status) and with propensity adjustment.

RESULTS

Current cardioprotective medication exposure status as compared to not exposed was associated with lower adjusted hazard ratios (AHRs) for mortality, though the magnitude depended upon the proportion of prior weeks with medication (duration) and the number of switches between active and non-active use (switches) (AHR range 0.54-0.90). Combined CVD-endpoints depended upon the proportion of weeks on medication: AHR = 1.18 for 10% and AHR = 0.90 for 90% of weeks. Combined CVD-endpoint was also lower for patients with fewer switches.

CONCLUSIONS

Effectiveness depends not only on having a drug available but is tempered by duration and stability of use, likely reflecting variation in clinical stability and patient behavior.

Germline BRCA mutation evaluation in a prospective triple-negative breast cancer registry: implications for hereditary breast and/or ovarian cancer syndrome testing

NCCN guidelines recommend genetic testing for all triple-negative breast cancer (TNBC) patients aged ≤60 years. However, due to the lack of prospective information in unselected patients, these guidelines are not uniformly adopted by clinicians and insurance carriers. The aim of this study was to determine the prevalence of BRCA mutations and evaluate the utility of NCCN guidelines in unselected TNBC population. Stage I-IV TNBC patients were enrolled on a prospective registry at academic and community practices. All patients underwent BRCA1/2 testing. Significant family history (SFH) was defined >1 relative with breast cancer at age ≤50 or ≥1 relative with ovarian cancer. Mutation prevalence in the entire cohort and subgroups was calculated. 207 TNBC patients were enrolled between 2011 and 2013. Racial/ethnic distribution: Caucasian (80 %), African-American (14 %), Ashkenazi (1 %). Deleterious BRCA1/2 mutations were identified in 15.4 % (32/207) of patients (BRCA1:11.1 %, BRCA2:4.3 %). SFH reported by 36 % of patients. Mutation prevalence in patients with and without SFH was 31.6 and 6.1 %, respectively. When assessed by age at TNBC diagnosis, the mutation prevalences were 27.6 % (≤50 years), 11.4 % (51-60 years), and 4.9 % (≥61 years). Using SFH or age ≤50 as criteria, 25 and 34 % of mutations, respectively, were missed. Mutation prevalence in patients meeting NCCN guidelines was 18.3 % (32/175) and 0 % (0/32) in patients who did not meet guidelines (p = .0059). In this unselected academic and community population with negligible Ashkenazi representation, we observed an overall BRCA mutation prevalence rate of 15.4 %. BRCA testing based on NCCN guidelines identified all carriers supporting its routine application in clinical practice for TNBC.

Derivation and validation of a formula to estimate risk for 30-day readmission in medical patients

OBJECTIVE

To create a simple readmission risk-prediction tool that can be generated easily at the bedside by physicians, nurses, care coordinators and discharge planners.

DESIGN

Retrospective cohort study.

SETTING

Tertiary academic medical center.

PARTICIPANTS

Inpatients aged 18 and older on general internal medicine services.

MEASURES

Predictor variables included age, prior hospitalization, high-risk diagnoses, high-risk medications, polypharmacy, depression, use of palliative care and a cumulative score summing these factors (readmission risk score-RRS). The main outcome measure was 30-day readmission. Predictive values were calculated.

RESULTS

Readmission increased linearly from 4.9% of those whose RRS score was 0-37.5% of those with highest risk scores (P = 0.0002). We derived a simple formula for readmission risk as 8 and 4% more for each additional readmission risk factor. The positive predictive value for RRS >0 was low, while the negative predictive value for this cutoff was 95%.

CONCLUSIONS

An easily calculated 7-point score can be used to estimate readmission risk. This tool may be particularly useful for identifying lower risk patients who may not require intensive intervention, thus aiding in appropriate targeting of resources.