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Search Results: 1 - 10 of 118345 matches for " Jimmy T. Efird "
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Season of Birth and Risk for Adult Onset Glioma
Jimmy T. Efird
International Journal of Environmental Research and Public Health , 2010, DOI: 10.3390/ijerph7051913
Abstract: Adult onset glioma is a rare cancer which occurs more frequently in Caucasians than African Americans, and in men than women. The etiology of this disease is largely unknown. Exposure to ionizing radiation is the only well established environmental risk factor, and this factor explains only a small percentage of cases. Several recent studies have reported an association between season of birth and glioma risk. This paper reviews the plausibility of evidence focusing on the seasonal interrelation of farming, allergies, viruses, vitamin D, diet, birth weight, and handedness. To date, a convincing explanation for the occurrence of adult gliomas decades after a seasonal exposure at birth remains elusive.
An Efficient Gatekeeper Algorithm for Detecting GxE
Jimmy T. Efird
Cancer Informatics , 2010,
Abstract: The risk for many complex diseases is believed to be a result of the interactive effects of genetic and environmental factors. Developing efficient techniques to identify gene-environment interactions (GxE) is important for unraveling the etiologic basis of many modern day diseases including cancer. The problem of false positives and false negatives continues to pose significant roadblocks to detecting GxE and informing targeted public health screening and intervention. A heuristic gatekeeper method is presented to guide the selection of single nucleotide polymorphisms (SNPs) in the design phase of a GxE study.
Computing Power and Sample Size for Informational Odds Ratio
Jimmy T. Efird
International Journal of Environmental Research and Public Health , 2013, DOI: 10.3390/ijerph10105239
Abstract: The informational odds ratio (IOR) measures the post-exposure odds divided by the pre-exposure odds ( i.e., information gained after knowing exposure status). A desirable property of an adjusted ratio estimate is collapsibility, wherein the combined crude ratio will not change after adjusting for a variable that is not a confounder. Adjusted traditional odds ratios (TORs) are not collapsible. In contrast, Mantel-Haenszel adjusted IORs, analogous to relative risks (RRs) generally are collapsible. IORs are a useful measure of disease association in case-referent studies, especially when the disease is common in the exposed and/or unexposed groups. This paper outlines how to compute power and sample size in the simple case of unadjusted IORs.
Grand Challenge: Understanding Survival Paradoxes in Epidemiology
Jimmy T. Efird,Wesley T. O’Neal,Alan P. Kypson
Frontiers in Public Health , 2013, DOI: 10.3389/fpubh.2013.00003
Abstract:
Informational Odds Ratio: A Useful Measure of Epidemiologic Association in Environment Exposure Studies
Jimmy T. Efird, Suzanne Lea, Amanda Toland and Christopher J. Phillips
Environmental Health Insights , 2012, DOI: 10.4137/EHI.S9236
Abstract: The informational odds ratio (IOR) measures the post-exposure odds divided by the pre-exposure odds (ie, information gained after knowing exposure status). A desirable property of an adjusted ratio estimate is collapsibility (ie, the combined crude ratio will not change after adjusting for a variable that is not a confounder). Adjusted traditional odds ratios (TORs) are not collapsible. In contrast, Mantel-Haenszel adjusted IORs generally are collapsible. IORs are a useful measure of disease association in environmental case-referent studies, especially when the disease is common in the exposed and/or unexposed groups.
Informational Odds Ratio: A Useful Measure of Epidemiologic Association in Environment Exposure Studies
Jimmy T. Efird,,Suzanne Lea,Amanda Tol,Christopher J. Phillips
Environmental Health Insights , 2012,
Abstract:
Blocked Randomization with Randomly Selected Block Sizes
Jimmy Efird
International Journal of Environmental Research and Public Health , 2011, DOI: 10.3390/ijerph8010015
Abstract: When planning a randomized clinical trial, careful consideration must be given to how participants are selected for various arms of a study. Selection and accidental bias may occur when participants are not assigned to study groups with equal probability. A simple random allocation scheme is a process by which each participant has equal likelihood of being assigned to treatment versus referent groups. However, by chance an unequal number of individuals may be assigned to each arm of the study and thus decrease the power to detect statistically significant differences between groups. Block randomization is a commonly used technique in clinical trial design to reduce bias and achieve balance in the allocation of participants to treatment arms, especially when the sample size is small. This method increases the probability that each arm will contain an equal number of individuals by sequencing participant assignments by block. Yet still, the allocation process may be predictable, for example, when the investigator is not blind and the block size is fixed. This paper provides an overview of blocked randomization and illustrates how to avoid selection bias by using random block sizes.
The Effect of Race and Chronic Obstructive Pulmonary Disease on Long-Term Survival after Coronary Artery Bypass Grafting
Jimmy T. Efird,Wesley T. O’Neal,Jason B. O’Neal,Alan P. Kypson
Frontiers in Public Health , 2013, DOI: 10.3389/fpubh.2013.00004
Abstract: Background: Chronic obstructive pulmonary disease (COPD) is a known predictor of decreased long-term survival after coronary artery bypass grafting (CABG). Differences in survival by race have not been examined.
Animal Viruses, Bacteria, and Cancer: A Brief Commentary
Jimmy T. Efird,Stephen W. Davies,Wesley T. O’Neal,Ethan J. Anderson
Frontiers in Public Health , 2014, DOI: 10.3389/fpubh.2014.00014
Abstract: Animal viruses and bacteria are ubiquitous in the environment. However, little is known about their mode of transmission and etiologic role in human cancers, especially among high-risk groups (e.g., farmers, veterinarians, poultry plant workers, pet owners, and infants). Many factors may affect the survival, transmissibility, and carcinogenicity of these agents, depending on the animal-host environment, hygiene practices, climate, travel, herd immunity, and cultural differences in food consumption and preparation. Seasonal variations in immune function also may increase host susceptibility at certain times of the year. The lack of objective measures, inconsistent study designs, and sources of epidemiologic bias (e.g., residual confounding, recall bias, and non-randomized patient selection) are some of the factors that complicate a clear understanding of this subject.
Potential Risk Factors for Cutaneous Squamous Cell Carcinoma include Oral Contraceptives: Results of a Nested Case-Control Study
Maryam M. Asgari,Jimmy T. Efird,E. Margaret Warton,Gary D. Friedman
International Journal of Environmental Research and Public Health , 2010, DOI: 10.3390/ijerph7020427
Abstract: Recently, a population-based case-control study observed a 60% increased odds ratio (OR) for cutaneous squamous cell carcinoma (SCC) among women who had ever used oral contraceptives (OCs) compared with non users (95% confidence interval (CI) = 1.0–2.5). To further characterize the putative association between OC use and SCC risk, we conducted a nested case-control study using a large retrospective cohort of 111,521 Kaiser Permanente Northern California members. Multivariable conditional logistic regression was used to estimate ORs and CIs adjusting for known and hypothesized SCC risk factors. Pre-diagnostic OC use was associated with a statistically significant increased OR for SCC in univariate analysis (OR = 2.4, CI = 1.2–4.8), with borderline statistical significance in multivariable analysis (CI = 2.0, CI = 0.91–4.5). Given the high incidence of SCC in the general population and the prevalent use of OCs among women in the United States, there is a need for more large, carefully designed epidemiologic studies to determine whether the observed association between OC use and SCC can be replicated and to better understand the etiologic basis of an association if one exists.
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