Biostatistics Commons^™

Targeted Bayesian Learning, Ivan Diaz Munoz, Alan E. Hubbard, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

Targeted maximum likelihood estimation (van der Laan & Rubin 2006) is a loss-based semi-parametric estimation method that yields a substitution estimator of a target parameter of the probability distribution of the data that solves the efficient influence curve estimating equation, and thereby yields a double robust locally efficient estimator of the parameter of interest, under regularity conditions. The Bayesian paradigm is concerned with including the researcher’s prior uncertainty about the parameter through a prior distribution, which combined with the likelihood yields a posterior distribution for the parameter that reflects the researcher’s posterior uncertainty. In this paper, we present a way …

Fast, Flexible Function-On-Scalar Regression, With An Application To Brain Development, Philip T. Reiss, Lei Huang

Philip T. Reiss

No abstract provided.

Landmark Prediction Of Survival, Layla Parast, Tianxi Cai

Harvard University Biostatistics Working Paper Series

No abstract provided.

Diagnosing And Responding To Violations In The Positivity Assumption, Maya L. Petersen, Kristin Porter, Susan Gruber, Yue Wang, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

The assumption of positivity or experimental treatment assignment requires that observed treatment levels vary within confounder strata. This article discusses the positivity assumption in the context of assessing model and parameter-specific identifiability of causal effects. Positivity violations occur when certain subgroups in a sample rarely or never receive some treatments of interest. The resulting sparsity in the data may increase bias with or without an increase in variance and can threaten valid inference. The parametric bootstrap is presented as a tool to assess the severity of such threats and its utility as a diagnostic is explored using simulated data. Several …

Stratifying Subjects For Treatment Selection With Censored Event Time Data From A Comparative Study, Lihui Zhao, Tianxi Cai, Lu Tian, Hajime Uno, Scott D. Solomon, L. J. Wei

Harvard University Biostatistics Working Paper Series

No abstract provided.

Sample Size And Statistical Power Considerations In High-Dimensionality Data Settings: A Comparative Study Of Classification Algorithms, Yu Guo, Armin Garber, Raji Balasubramanian

Raji Balasubramanian

Background: Data generated using ‘omics’ technologies are characterized by high dimensionality, where the number of features measured per subject vastly exceeds the number of subjects in the study. In this paper, we consider issues relevant in the design of biomedical studies in which the goal is the discovery of a subset of features and an associated algorithm that can predict a binary outcome, such as disease status. We compare the performance of four commonly used classifiers (K-Nearest Neighbors, Prediction Analysis for Microarrays, Random Forests and Support Vector Machines) in high-dimensionality data settings. We evaluate the effects of varying levels of …

Health Benefits Of Increased Walking For Sedentary, Generally Healthy Older Adults: Using Longitudinal Data To Approximate An Intervention Trial, Paula Diehr

Paula Diehr

BACKGROUND: Older adults are often advised to walk more, but randomized trials have not conclusively established the benefits of walking in this age group. Typical analyses based on observational data may have biased results. Here, we propose a "limited-bias," more interpretable estimate of the health benefits to sedentary healthy older adults of walking more, using longitudinal data from the Cardiovascular Health Study. METHODS: The number of city blocks walked per week, collected annually, was classified as sedentary (<7 blocks per>week), somewhat active, or active (>or=28). Analysis was restricted to persons sedentary and healthy in the first 2 years. In Year …

Spousal Concordance In Academic Achievements And Intelligence And Family-Based Association Studies Identified Novel Loci Associated With Intelligence., Yue Pan

Electronic Theses and Dissertations

Assortative Mating, the tendency for mate selection to occur on the basis of similar traits, plays an essential role in understanding the genetic variation on academic achievements and intelligence (IQ). It is an important mechanism explaining spousal concordance. We used principal component analysis (PCA) for spousal correlation. There is a significant positive correlation between spouses by the new variable PC1 (correlation coefficient=0.515, p<0.0001). We further research the genetic factor that affects IQ by using the same data. We performed a low density genome-wide association (GWA) analysis with a family-based association test to identify genetic variants that associated with intelligence as measured by WAIS full-score IQ (FSIQ). NTM at 11q25 (rs411280, p=0.000764) and NR3C2 at 4q31.23 (rs3846329, p=0.000675) were 2 novel genes that haven't been associated with IQ from other studies. This study may serve as a resource for replication in other populations and a foundation for future investigations.

Distribution Of Health Care Expenditures For Hiv-Infected Patients, Ray Y. Chen, Neil A. Accortt, Andrew O. Westfall, Michael J. Mugavero, James L. Raper, Gretchen A. Cloud, Beth K. Stone, Jerome Carter, Stephanie Call, Maria Pisu, Jeroan J. Allison, Michael S. Saag

Jeroan J. Allison

BACKGROUND: Health care expenditures for persons infected with human immunodeficiency virus (HIV) in the United State determined on the basis of actual health care use have not been reported in the era of highly active antiretroviral therapy.

METHODS: Patients receiving primary care at the University of Alabama at Birmingham HIV clinic were included in the study. All encounters (except emergency room visits) that occurred within the University of Alabama at Birmingham Hospital System from 1 March 2000 to 1 March 2001 were analyzed. Medication expenditures were determined on the basis of 2001 average wholesale price. Hospitalization expenditures were determined on …

Trends In Aids-Defining And Non-Aids-Defining Malignancies Among Hiv-Infected Patients: 1989-2002, Roger Bedimo, Ray Y. Chen, Neil A. Accortt, James L. Raper, Carol Linn, Jeroan J. Allison, John Dubay, Michael S. Saag, Craig J. Hoesley

Jeroan J. Allison

In a comparison of rates of acquired immunodeficiency syndrome (AIDS)-defining malignancies (ADMs) for 1989-1996 versus 1997-2002, we found a decrease in ADMs (rate ratio, 0.31; P<.0001) and a significant increase in non-AIDS-defining malignancies (non-ADMs; rate ratio, 10.87; P<.0002). The mean CD4 cell count was lower among patients with ADMs than among those with non-ADMs. A longer duration of survival during highly active antiretroviral therapy might explain the increasing incidence of non-ADMs.

A Bayesian Approach To Dose-Response Assessment And Drug-Drug Interaction Analysis: Application To In Vitro Studies, Violeta G. Hennessey

Dissertations & Theses (Open Access)

The considerable search for synergistic agents in cancer research is motivated by the therapeutic benefits achieved by combining anti-cancer agents. Synergistic agents make it possible to reduce dosage while maintaining or enhancing a desired effect. Other favorable outcomes of synergistic agents include reduction in toxicity and minimizing or delaying drug resistance. Dose-response assessment and drug-drug interaction analysis play an important part in the drug discovery process, however analysis are often poorly done. This dissertation is an effort to notably improve dose-response assessment and drug-drug interaction analysis.

The most commonly used method in published analysis is the Median-Effect Principle/Combination Index method …

Body Mass Index, Treatment Practices, And Mortality In Patients With Acute Heart Failure, Timothy Fitzgibbons, Olga Hardy, Darleen Lessard, Joel Gore, Jorge Yarzebski, Robert Goldberg

Jorge L. Yarzebski

OBJECTIVES: Obesity is associated with an increased risk of heart failure (HF). Among patients presenting with acute HF, however, differences in clinical characteristics, treatment regimens, and short-term prognosis of varying weights are largely unknown, particularly from a broader population-based perspective. METHODS: A total of 3722 patients admitted with acute HF to 11 greater Worcester (Massachusetts, USA) hospitals during 1995 and 2000 were categorized as being lean (n = 216), normal weight (n = 1465), overweight (n = 1007), or obese (n = 1034) at the time of hospitalization. RESULTS: Obese patients with decompensated HF were significantly younger (mean age = …

Prognosis Of Acute Myocardial Infarction Complicated By Complete Heart Block (The Worcester Heart Attack Study), Robert Goldberg, Juan Zevallos, Jorge Yarzebski, Joseph Alpert, Joel Gore, Z. Chen, James Dalen

Jorge L. Yarzebski

As part of a community-based study of patients hospitalized with acute myocardial infarction (AMI) in the Worcester, Massachusetts, metropolitan area, changes over time in the incidence rates of complete heart block (CHB) complicating AMI, and the prognostic impact of CHB on the in-hospital and long-term survival of these patients were examined. In all, 4,762 patients with validated AMI hospitalized at 16 hospitals in the Worcester metropolitan area during 1975, 1978, 1981, 1984, 1986 and 1988 constituted the study sample. The incidence rates of CHB complicating AMI remained relatively stable at 5.8% over the 13-year (1975 to 1988) period studied. The …

Changes Over Time In The Use Of Aspirin In Patients Hospitalized With Acute Myocardial Infarction (1975 To 1997): A Population-Based Perspective, Elizabeth Jackson, Ramya Sivasubramian, Frederick Spencer, Jorge Yarzebski, Darleen Lessard, Joel Gore, Robert Goldberg

Jorge L. Yarzebski

OBJECTIVE: The purpose of this study was to examine 2 decade-long trends in the use of aspirin and associated outcomes in patients hospitalized with acute myocardial infarction. BACKGROUND: Aspirin has been shown to be beneficial in the secondary prevention of AMI. However, little is known about changes over time in the use of aspirin in patients hospitalized with AMI and associated outcomes, particularly from a more generalizable population-based perspective. METHODS: We examined trends in aspirin use and hospital and long-term outcomes in 9336 metropolitan Worcester, Mass, residents hospitalized with validated AMI in all area hospitals between 1975 and 1997. RESULTS: …

Thirty-Year Trends (1975-2005) In The Magnitude, Patient Characteristics, And Hospital Outcomes Of Patients With Acute Myocardial Infarction Complicated By Ventricular Fibrillation, Robert Goldberg, Jorge Yarzebski, Frederick Spencer, Juan Zevallos, Darleen Lessard, Joel Gore

Jorge L. Yarzebski

Limited contemporary data are available describing the incidence rates, hospital prognosis, and factors associated with the occurrence of ventricular fibrillation (VF) in patients hospitalized with acute myocardial infarction (AMI). The objectives of our study were to examine 3-decade-long trends (1975 to 2005) in the magnitude, predictors, and hospital case-fatality rates associated with VF in residents of a large New England metropolitan area hospitalized at all area medical centers with an uncomplicated AMI. The study population consisted of 7,472 residents of the Worcester (Massachusetts) metropolitan area hospitalized with an uncomplicated AMI in 15 annual periods from 1975 to 2005. The overall …

Temporal Trends (1975 Through 1990) In The Incidence And Case-Fatality Rates Of Primary Ventricular Fibrillation Complicating Acute Myocardial Infarction. A Communitywide Perspective, David Chiriboga, Jorge Yarzebski, Robert Goldberg, Joel Gore, Joseph Alpert

Jorge L. Yarzebski

BACKGROUND: As part of a population-based study of acute myocardial infarction, we examined changes over time in the incidence and in-hospital case-fatality rates of primary ventricular fibrillation complicating acute myocardial infarction. METHODS AND RESULTS: Patients with validated acute myocardial infarction hospitalized at 16 hospitals in the Worcester, Mass, metropolitan area between 1975 and 1990 comprised the study sample. During the 15-year study period, 5.1% of patients developed primary ventricular fibrillation in the setting of uncomplicated acute myocardial infarction, with this rate remaining relatively constant over time. Both age- and multivariable-adjusted analyses showed no significant trend in the incidence rates of …

Coronary Heart Disease: Epidemiology, Risk Factors, And Temporal Trends, Robert Goldberg, Jorge Yarzebski

Jorge L. Yarzebski

Citation: Goldberg RJ, Yarzebski JL. Coronary Heart Disease: Epidemiology, Risk Factors, and Temporal Trends. Chapter 1, pp. 3 24. In Lifestyle Medicine. Rippe JM (Ed.). 1999. Blackwell Science Publishers.

Long-Term Trends (1986-2003) In The Use Of Coronary Reperfusion Strategies In Patients Hospitalized With Acute Myocardial Infarction In Central Massachusetts, Robert J. Goldberg, Frederick A. Spencer, Joseph Okolo, Darleen M. Lessard, Jorge L. Yarzebski, Joel M. Gore

Jorge L. Yarzebski

BACKGROUND: The objectives of our study were to examine long-term (1986-2003) trends in the use of percutaneous coronary interventions (PCI) and thrombolytic therapy in the management of patients hospitalized at all Central Massachusetts medical centers with acute myocardial infarction (AMI). Our secondary study goal was to examine factors associated with use of these coronary reperfusion strategies. Limited contemporary data are available about changing trends in the use of coronary reperfusion strategies, particularly from a population-based perspective. METHODS: The sample consisted of 9422 greater Worcester (MA) residents hospitalized with AMI at all metropolitan Worcester medical centers in 10 annual periods between …

Decade-Long Trends (1986 To 1997) In The Medical Treatment Of Patients With Acute Myocardial Infarction: A Community-Wide Perspective, Frederick Spencer, George Scleparis, Robert Goldberg, Jorge Yarzebski, Darleen Lessard, Joel Gore

Jorge L. Yarzebski

BACKGROUND: Although there are an increasing number and variety of medications available for the treatment of patients with acute myocardial infarction (AMI), few data are available describing recent, and changes over time in, use of different cardiac medications in patients with AMI from a more generalizable, community-wide perspective. Moreover, it is unclear whether the demographic and clinical profile of patients receiving these agents is similar or varies according to the type of agent prescribed. METHODS AND RESULTS: The purpose of this study was to examine recent patterns and changes over a decade-long period (1986 to 1997) in the use of …

A Community-Wide Perspective Of Gender Differences And Temporal Trends In The Use Of Diagnostic And Revascularization Procedures For Acute Myocardial Infarction, David Chiriboga, Jorge Yarzebski, Robert Goldberg, Z. Chen, Jerry Gurwitz, Joel Gore, Joseph Alpert, James Dalen

Jorge L. Yarzebski

This study compares the overall use, as well as temporal trends, of various diagnostic and revascularization procedures for acute myocardial infarction (AMI) in men and women. The study sample comprised a total of 2,924 men and 1,838 women with validated AMI admitted to any of the 16 teaching and community hospitals in the Worcester, Massachusetts, metropolitan area during 1975, 1978, 1981, 1984, 1986 and 1988. During the period under study there was a significant increase in use of each of the examined procedures during hospitalization for AMI in both men and women. Increasing use of multiple procedures was also seen …