Physical Sciences and Mathematics Commons^™

Targeted Maximum Likelihood Estimation Of Natural Direct Effect, Wenjing Zheng, Mark Van Der Laan

Wenjing Zheng

In many causal inference problems, one is interested in the direct causal effect of an exposure on an outcome of interest that is not mediated by certain intermediate variables. Robins and Greenland (1992) and Pearl (2000) formalized the definition of two types of direct effects (natural and controlled) under the counterfactual framework. Since then, identifiability conditions for these effects have been studied extensively. By contrast, considerably fewer efforts have been invested in the estimation problem of the natural direct effect. In this article, we propose a semiparametric efficient, multiply robust estimator for the natural direct effect of a binary treatment …

Bayesian Analysis Of Hypothesis Testing Problems For General Population: A Kullback–Leibler Alternative, Naveen Bansal, Gholamhossein Hamedani, Ru Sheng

Naveen Bansal

We consider a hypothesis problem with directional alternatives. We approach the problem from a Bayesian decision theoretic point of view and consider a situation when one side of the alternatives is more important or more probable than the other. We develop a general Bayesian framework by specifying a mixture prior structure and a loss function related to the Kullback–Leibler divergence. This Bayesian decision method is applied to Normal and Poisson populations. Simulations are performed to compare the performance of the proposed method with that of a method based on a classical z-test and a Bayesian method based on the …

Creating Composite Age Groups To Smooth Percentile Rank Distributions Of Small Samples, Francesca Lopez, Amy Olson, Naveen Bansal

Naveen Bansal

Individually administered tests are often normed on small samples, a process that may result in irregularities within and across various age or grade distributions. Test users often smooth distributions guided by Thurstone assumptions (normality and linearity) to result in norms that adhere to assumptions made about how the data should look. Test users, however, may come across particular tests or sets of data in which the Thurstone assumptions are untenable. When users expect deviations from normality within age or grade, an alternate method is desirable. The authors present a relatively simple procedure that allows the user to treat observed raw …

National Survey Of Adolescent Well-Being (Nscaw): A Comparison Of Model And Design Based Analyses Of Cognitive Stimulation Scores, Marianne Bertolet, Howard Seltman, Joel Greenhouse, Kelly Kelleher

Joel B Greenhouse

Understanding and protecting vulnerable children is key to helping them become productive members of society. The Department of Health and Human Services sponsored the National Survey of Child and Adolescent Well-Being (NSCAW) to better understand the lives of children who come into contact with the child welfare system. This paper uses the NSCAW data to investigate the role of maternal depression and maternal substance abuse on a child's cognitive stimulation scores for a subset of the children. An investigation of the survey methodology and the actual data led to some manipulation of the data and assumptions for the analysis. The …

Meta-Analysis: In Practice, Joel Greenhouse

Joel B Greenhouse

The practice of meta-analysis is concerned with the details of implementation of a research synthesis that ensure the validity and robustness of the results from that synthesis. In this article, selected topics are discussed that represent current intellectual themes in the practice of meta-analysis, such as, (i) the role of decisions and judgments, particularly judgments about similarity of studies; (ii) the importance of sensitivity analysis to investigate the robustness of those decisions; and (iii) the role research synthesis plays in the process of scientific discovery. Brief illustrations of the role meta-analysis plays in explanation, program evaluation, and in informing policy …

Natural History Of Concentric Left Ventricular Geometry In Community-Dwelling Older Adults Without Heart Failure During Seven Years Of Follow-Up, Ravi Desai, Mustafa Ahmed, Marjan Mujib, Inmaculada Aban, Michael Zile, Ali Ahmed

Ravi V Desai MD

No abstract provided.

Absence Of Obesity Paradox In Patients With Chronic Heart Failure And Diabetes Mellitus: A Propensity-Matched Study, Chris Adamopoulos, Philippe Meyer, Ravi Desai, Kyparissi Karatzidou, Fernando Ovalle, Michel White, Inmaculada Aban, Thomas Love, Prakash Deedwania, Stefan Anker, Ali Ahmed

Ravi V Desai MD

No abstract provided.

Relation Of Baseline Systolic Blood Pressure And Long-Term Outcomes In Ambulatory Patients With Chronic Mild To Moderate Heart Failure, Maciej Banach, Vikas Bhatia, Margaret Feller, Marjan Mujib, Ravi Desai, Mustafa Ahmed, Jason Guichard, Inmaculada Aban, Thomas Love, Wilbert Aronow, Michel White, Prakash Deedwania, Gregg Fonarow, Ali Ahmed

Ravi V Desai MD

No abstract provided.

Warfarin Use And Outcomes In Patients With Advanced Chronic Systolic Heart Failure Without Atrial Fibrillation, Prior Thromboembolic Events, Or Prosthetic Valves, Marjan Mujib, Abu-Ahmed Rahman, Ravi Desai, Mustafa Ahmed, Margaret Feller, Inmaculada Aban, Tomas Love, Michel White, Prakash Deedwania, Wilbert Aronow, Gregg Fonarow, Ali Ahmed

Ravi V Desai MD

No abstract provided.

Influence Of Co-Existing Atrial Fibrillation On The Efficacy Of Atorvastatin Treatment In Patients With Dilated Cardiomyopathy: A Pilot Study, Agata Bielecka-Dabrowa, Jan Goch, Jacek Rysz, Marek Maciejewski, Ravi Desai, Wilbert Aronow

Ravi V Desai MD

No abstract provided.

Rheumatic Heart Disease And Risk Of Incident Heart Failure Among Community-Dwelling Older Adults: A Prospective Cohort Study, Marjan Mujib, Ravi Desai, Mustafa Ahmed, Jason Guichard, Margaret Feller, O Ekundayo, Prakash Deedwania, Mahboob Ali, Inmaculada Aban, Thomas Love, Michel White, Wilbert Aronow, Shahbudin Rahimtoola, Robert Bonow, Ali Ahmed

Ravi V Desai MD

No abstract provided.

Relationship Between Left And Right Ventricular Ejection Fractions In Chronic Advanced Systolic Heart Failure: Insights From The Best Trial, Ravi Desai, Philippe Meyer, Mustafa Ahmed, Marjan Mujib, Chris Adamopoulos, Michel White, Inmaculada Aban, Ami Iskandrian, Ali Ahmed

Ravi V Desai MD

No abstract provided.

Design And Rationale Of Studies Of Neurohormonal Blockade And Outcomes In Diastolic Heart Failure Using Optimize-Hf Registry Linked To Medicare Data, Yan Zhang, Meredith Kilgore, Tarun Arora, Marjan Mujib, O. Ekundayo, Inmaculada Aban, Margaret Feller, Ravi Desai, Thomas Love, Richard Allman, Gregg Fonarow, Ali Ahmed

Ravi V Desai MD

No abstract provided.

A Propensity-Matched Study Of The Association Of Diabetes Mellitus With Incident Heart Failure And Mortality Among Community-Dwelling Older Adults, Brita Roy, Pushkar Pawar, Ravi Desai, Gregg Fonarow, Marjan Mujib, Yan Zhang, Margaret Feller, Fernando Ovalle, Inmaculada Aban, Thomas Love, Ami Iskandrian, Prakash Deedwania, Ali Ahmed

Ravi V Desai MD

No abstract provided.

Heart Failure Is A Risk Factor For Incident Driving Cessation Among Community-Dwelling Older Adults: Findings From A Prospective Population Study, Richard Sims, Marjan Mujib, Gerald Mcgwin, Yan Zhang, Mustafa Ahmed, Ravi Desai, Inmaculada Aban, Patrick Sawyer, Stefan Anker, Ali Ahmed

Ravi V Desai MD

No abstract provided.

Managed Care, Hospice Use, Site Of Death, And Medical Expenditures In The Last Year Of Life, Ezekiel Emanuel, Arlene Ash, Wei Yu, Gail Gazelle, Norman Levinsky, Olga Saynina, Mark Mcclellan, Mark Moskowitz

wei yu

BACKGROUND: We examined deaths of Medicare beneficiaries in Massachusetts and California to evaluate the effect of managed care on the use of hospice and site of death and to determine how hospice affects the expenditures for the last year of life.

METHODS: Medicare data for beneficiaries in Massachusetts (n = 37 933) and California (n = 27 685) who died in 1996 were merged with each state's death certificate files to determine site and cause of death. Expenditure data were Health Care Financing Administration payments and were divided into 30-day periods from the date of death back 12 months.

RESULTS: …

Recognition And Resolution Of 'Comprehension Uncertainty' In Ai, Sukanto Bhattacharya, Kuldeep Kumar

Kuldeep Kumar

Handling uncertainty is an important component of most intelligent behaviour – so uncertainty resolution is a key step in the design of an artificially intelligent decision system (Clark, 1990). Like other aspects of intelligent systems design, the aspect of uncertainty resolution is also typically sought to be handled by emulating natural intelligence (Halpern, 2003; Ball and Christensen, 2009). In this regard, a number of computational uncertainty resolution approaches have been proposed and tested by Artificial Intelligence (AI) researchers over the past several decades since birth of Al as a scientific discipline in early 1950s post- publication of Alan Turing's landmark …

Estimating The Effect Of A Community-Based Intervention With Two Communities, Mark Van Der Laan, Maya Petersen, Wenjing Zheng

Wenjing Zheng

Due to the need to evaluate the effectiveness of community-based programs in practice, there is substantial interest in methods to estimate the causal effects of community-level treatments or exposures on individual level outcomes. The challenge one is confronted with is that different communities have different environmental factors affecting the individual outcomes, and all individuals in a community share the same environment and intervention. In practice, data are often available from only a small number of communities, making it difficult if not impossible to adjust for these environmental confounders. In this paper we consider an extreme version of this dilemma, in …

Compliance With The Centers For Disease Control And Prevention Recommendations For The Diagnosis And Treatment Of Sexually Transmitted Diseases, Bryan Kane, Linda Degutis, Helen Sayward, Gail D'Onofrio

Bryan G Kane MD

No abstract provided.

Evaluation Of Student Outcomes In Online Vs. Campus Biostatistics Education In A Graduate School Of Public Health, John Mcgready, Ron Brookmeyer

Ron Brookmeyer

Objective: To compare student outcomes between concurrent online and on-campus sections of an introductory biostatistics course offered at a U.S. school of public health in 2005. Methods: Enrolled students (95 online, 92 on-campus) were invited to participate in a confidential online survey. The course outcomes were compared between the two sections adjusting for differences in student characteristics. Results: Seventy-two online (76%) and 66 (72%) on-campus enrollees participated. Unadjusted final exam scores for the online and on-campus sections were respectively 85.1 and 86.3 (p = 0.50) in term 1, and 87.7 and 86.9 (p=0.58) in term 2. After adjustment for student …

Estimation Of Hiv Incidence Using Multiple Biomakers, Ron Brookmeyer, Jacob Konikoff, Oliver Laeyendecker, Susan Eshleman

Ron Brookmeyer

The incidence of human immunodeficiency virus (HIV) is the rate at which new HIV infections occur in populations. The development of accurate, practical, and cost-effective approaches to estimation of HIV incidence is a priority among researchers in HIV surveillance because of limitations with existing methods. In this paper, we develop methods for estimating HIV incidence rates using multiple biomarkers in biological samples collected from a cross-sectional survey. An advantage of the method is that it does not require longitudinal follow-up of individuals. We use assays for BED, avidity, viral load, and CD4 cell count data from clade B samples collected …

Instrumental Variable Analyses: Exploiting Natural Randomness To Understand Causal Mechanisms, Theodore Iwashyna, Edward Kennedy

Edward H. Kennedy

Instrumental variable analysis is a technique commonly used in the social sciences to provide evidence that a treatment causes an outcome, as contrasted with evidence that a treatment is merely associated with differences in an outcome. To extract such strong evidence from observational data, instrumental variable analysis exploits situations where some degree of randomness affects how patients are selected for a treatment. An instrumental variable is a characteristic of the world that leads some people to be more likely to get the specific treatment we want to study but does not otherwise change thosepatients’ outcomes. This seminar explains, in nonmathematical …

Improved Cardiovascular Risk Prediction Using Nonparametric Regression And Electronic Health Record Data, Edward Kennedy, Wyndy Wiitala, Rodney Hayward, Jeremy Sussman

Edward H. Kennedy

Use of the electronic health record (EHR) is expected to increase rapidly in the near future, yet little research exists on whether analyzing internal EHR data using flexible, adaptive statistical methods could improve clinical risk prediction. Extensive implementation of EHR in the Veterans Health Administration provides an opportunity for exploration. Our objective was to compare the performance of various approaches for predicting risk of cerebrovascular and cardiovascular (CCV) death, using traditional risk predictors versus more comprehensive EHR data. Regression methods outperformed the Framingham risk score, even with the same predictors (AUC increased from 71% to 73% and calibration also improved). …