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‣ Epidemiology Competency Development and Application to Training for Local and Regional Public Health Practitioners

Baseman, Janet G.; Marsden-Haug, Nicola; Holt, Victoria L.; Stergachis, Andy; Goldoft, Marcia; Gale, James L.
Fonte: Association of Schools of Public Health Publicador: Association of Schools of Public Health
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
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In 2002, the Northwest Center for Public Health Practice (NWCPHP) at the University of Washington initiated the Epidemiology Competencies Project, with the goal of developing competency-based epidemiology training for non-epidemiologist public health practitioners in the northwestern United States. An advisory committee consisting of epidemiology faculty and experienced public health practitioners developed the epidemiology competencies. NWCPHP used the competencies to guide the development of in-person trainings, a series of online epidemiology modules, and a Web-based repository of epidemiology teaching materials. The epidemiology competencies provided a framework for collaborative work between NWCPHP and local and regional public health partners to develop trainings that best met the needs of a particular public health organization. Evaluation surveys indicated a high level of satisfaction with the online epidemiology modules developed from the epidemiology competencies. However, measuring the effectiveness of -competency-based epidemiology training for expanding epidemiology knowledge and skills of the public health workforce remains a challenge.

‣ Are Lifetime Abstainers the Best Control Group in Alcohol Epidemiology? On the Stability and Validity of Reported Lifetime Abstention

Rehm, J.; Irving, H.; Ye, Y.; Kerr, W. C.; Bond, J.; Greenfield, T. K.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Lifetime abstainers have often been recommended as the comparison group in alcohol epidemiology. The objective of this study was to provide insight into the validity and stability of lifetime abstention by using data derived from the National Alcohol Survey, a national probability survey of US households conducted in 1984, and its 2 follow-up surveys conducted in 1990 and 1992. Results indicated that more than half (52.9%; all proportions were weighted to represent the US population) of those who reported never having a drink of any alcoholic beverage in the 1992 survey reported drinking in previous surveys. Depending on assumptions, this difference may result in an underestimation of alcohol-attributable mortality of 2%−15% in men and 2%−22% in women. Sociodemographic factors differentiated those who consistently reported lifetime abstention across surveys from the rest of the study population. Results suggest that using reported lifetime abstainers as a sole comparison group is problematic, especially if reporting is based on 1 measurement only. Establishing multiple measurement points and including irregular lifetime light drinkers with lifetime abstainers as the comparison group are recommended for future epidemiologic studies.

‣ A Comparison of Sample Size and Power in Case-Only Association Studies of Gene-Environment Interaction

Clarke, Geraldine M.; Morris, Andrew P.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Assuming continuous, normally distributed environmental and categorical genotype variables, the authors compare 6 case-only designs for tests of association in gene-environment interaction. Novel tests modeling the environmental variable as either the response or the predictor and allowing a genetic variable with multiallelic variants are included. The authors show that tests imposing the same genotypic pattern of inheritance perform similarly regardless of whether genotype is the response variable or the predictor variable. The novel tests using the genetic variable as the response variable are advantageous because they are robust to non-normally distributed environmental exposures. Dominance deviance—deviation from additivity in the main or interaction effects—is key to test performance: When it is zero or modest, tests searching for a trend with increasing risk alleles are optimal; when it is large, tests for genotypic effects are optimal. However, the authors show that dominance deviance is attenuated when it is observed at a proxy locus, which is common in genome-wide association studies, so large dominance deviance is likely to be rare. The authors conclude that the trend test is the appropriate tool for large-scale association scans where the true gene-environment interaction model is unknown. The common practice of assuming a dominant pattern of inheritance can cause serious losses of power in the presence of any recessive...

‣ Invited Commentary: Positivity in Practice

Westreich, Daniel; Cole, Stephen R.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Positivity, or the experimental treatment assignment assumption, requires that there be both exposed and unexposed participants at every combination of the values of the observed confounders in the population under study. Positivity is essential for inference but is often overlooked in practice by epidemiologists. This issue of the Journal includes 2 articles featuring discussions related to positivity. Here the authors define positivity, distinguish between deterministic and random positivity, and discuss the 2 relevant papers in this issue. In addition, the commentators illustrate positivity in simple 2 × 2 tables, as well as detail some ways in which epidemiologists may examine their data for nonpositivity and deal with violations of positivity in practice.

‣ Impact of Improved Classification on the Association of Human Papillomavirus With Cervical Precancer

Castle, Philip E.; Schiffman, Mark; Wheeler, Cosette M.; Wentzensen, Nicolas; Gravitt, Patti E.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Misclassification of exposure and surrogate endpoints of disease can obscure causal relations. Using data from the Atypical Squamous Cells of Undetermined Significance/Low-Grade Squamous Intraepithelial Lesion Triage Study (ALTS, 1997–2001), the authors explored the impact of exposure (human papillomavirus (HPV) detection) and endpoint (histologic cervical precancer) classification on their mutual association. Women referred into this study with an atypical squamous cells of undetermined significance Papanicolaou test with satisfactory results for all 4 HPV tests were included in this analysis (n = 3,215; 92.2%). HPV testing results were related to different definitions of cervical precancer, based on paired, worst 2-year histologic diagnoses, by calculating clinical sensitivity, specificity, and odds ratios. The authors found that HPV test sensitivity increased and specificity decreased with increasing certainty of cervical precancer, with HPV testing having the highest sensitivity (92%–98%) and lowest specificity (46%–54%) for consensus cervical intraepithelial neoplasia grade 3 (CIN 3). The overall accuracy of each HPV test, as measured by odds ratios, was greatest for consensus CIN-3 diagnoses, from 2- to 4-fold greater than for a less stringent precancer definition of any diagnosis of CIN 2 or more severe. In summary...

‣ Invited Commentary: Human Papillomavirus Infection and Risk of Cervical Precancer—Using the Right Methods to Answer the Right Questions

Franco, Eduardo L.; Tota, Joseph
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Epidemiologists are well aware of the negative consequences of measurement error in exposure and outcome variables to their ability to detect putative causal associations. However, empirical proof that remedying the misclassification problem improves estimates of epidemiologic effect is seldom examined in detail. Of all areas in cancer epidemiology, perhaps the best example of the consequences of misclassification and of the steps taken to circumvent them was the pursuit, beginning in the mid-1980s, of the human papillomavirus (HPV) infection–cervical cancer association. The stakes were high: Had the wrong conclusions been reached epidemiologists would have been led astray in the search for competing hypotheses for the sexually transmissible agent causing cervical cancer or in ascribing to HPV infection a mere ancillary role among many lifestyle, hormonal, and environmental factors. The article by Castle et al. in this issue of the Journal (Am J Epidemiol. 2010;171(2):155–163) provides a detailed account of the joint influences of improved HPV and cervical precancer measurements in gradually unveiling the strong magnitude of the underlying association between viral exposure and cervical lesion risk. In this commentary, the authors extend the findings of Castle et al. by providing additional empirical evidence in support of their arguments.

‣ Use of a Medical Records Linkage System to Enumerate a Dynamic Population Over Time: The Rochester Epidemiology Project

St. Sauver, Jennifer L.; Grossardt, Brandon R.; Yawn, Barbara P.; Melton, L. Joseph; Rocca, Walter A.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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The Rochester Epidemiology Project (REP) is a unique research infrastructure in which the medical records of virtually all persons residing in Olmsted County, Minnesota, for over 40 years have been linked and archived. In the present article, the authors describe how the REP links medical records from multiple health care institutions to specific individuals and how residency is confirmed over time. Additionally, the authors provide evidence for the validity of the REP Census enumeration. Between 1966 and 2008, 1,145,856 medical records were linked to 486,564 individuals in the REP. The REP Census was found to be valid when compared with a list of residents obtained from random digit dialing, a list of residents of nursing homes and senior citizen complexes, a commercial list of residents, and a manual review of records. In addition, the REP Census counts were comparable to those of 4 decennial US censuses (e.g., it included 104.1% of 1970 and 102.7% of 2000 census counts). The duration for which each person was captured in the system varied greatly by age and calendar year; however, the duration was typically substantial. Comprehensive medical records linkage systems like the REP can be used to maintain a continuously updated census and to provide an optimal sampling framework for epidemiologic studies.

‣ Implementation of G-Computation on a Simulated Data Set: Demonstration of a Causal Inference Technique

Snowden, Jonathan M.; Rose, Sherri; Mortimer, Kathleen M.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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The growing body of work in the epidemiology literature focused on G-computation includes theoretical explanations of the method but very few simulations or examples of application. The small number of G-computation analyses in the epidemiology literature relative to other causal inference approaches may be partially due to a lack of didactic explanations of the method targeted toward an epidemiology audience. The authors provide a step-by-step demonstration of G-computation that is intended to familiarize the reader with this procedure. The authors simulate a data set and then demonstrate both G-computation and traditional regression to draw connections and illustrate contrasts between their implementation and interpretation relative to the truth of the simulation protocol. A marginal structural model is used for effect estimation in the G-computation example. The authors conclude by answering a series of questions to emphasize the key characteristics of causal inference techniques and the G-computation procedure in particular.

‣ Use of Surveillance, Epidemiology, and End Results-Medicare Data to Conduct Case-Control Studies of Cancer Among the US Elderly

Engels, Eric A.; Pfeiffer, Ruth M.; Ricker, Winnie; Wheeler, William; Parsons, Ruth; Warren, Joan L.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Cancer is an important cause of morbidity in the elderly, and many medical conditions and treatments influence cancer risk. The Surveillance, Epidemiology, and End Results (SEER)-Medicare database can be used to conduct population-based case-control studies that elucidate the etiology of cancer among the US elderly. SEER-Medicare links data on malignancies ascertained through SEER cancer registries to claims from Medicare, the US government insurance program for people over age 65 years. Under one approach described herein, elderly cancer cases are ascertained from SEER data (1987–2005). Matched controls are selected from a 5% random sample of Medicare beneficiaries. Risk factors of interest, including medical conditions and procedures, are identified by using linked Medicare claims. Strengths of this design include the ready availability of data, representative sampling from the US elderly population, and large sample size (e.g., under one scenario: 1,176,950 cases, including 221,389 prostate cancers, 185,853 lung cancers, 138,041 breast cancers, and 124,442 colorectal cancers; and 100,000 control subjects). Limitations reflect challenges in exposure assessment related to Medicare claims: restricted range of evaluable risk factors...

‣ Taking Advantage of the Strengths of 2 Different Dietary Assessment Instruments to Improve Intake Estimates for Nutritional Epidemiology

Carroll, Raymond J.; Midthune, Douglas; Subar, Amy F.; Shumakovich, Marina; Freedman, Laurence S.; Thompson, Frances E.; Kipnis, Victor
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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With the advent of Internet-based 24-hour recall (24HR) instruments, it is now possible to envision their use in cohort studies investigating the relation between nutrition and disease. Understanding that all dietary assessment instruments are subject to measurement errors and correcting for them under the assumption that the 24HR is unbiased for usual intake, here the authors simultaneously address precision, power, and sample size under the following 3 conditions: 1) 1–12 24HRs; 2) a single calibrated food frequency questionnaire (FFQ); and 3) a combination of 24HR and FFQ data. Using data from the Eating at America’s Table Study (1997–1998), the authors found that 4–6 administrations of the 24HR is optimal for most nutrients and food groups and that combined use of multiple 24HR and FFQ data sometimes provides data superior to use of either method alone, especially for foods that are not regularly consumed. For all food groups but the most rarely consumed, use of 2–4 recalls alone, with or without additional FFQ data, was superior to use of FFQ data alone. Thus, if self-administered automated 24HRs are to be used in cohort studies, 4–6 administrations of the 24HR should be considered along with administration of an FFQ.

‣ Correlated Biomarker Measurement Error: An Important Threat to Inference in Environmental Epidemiology

Pollack, A. Z.; Perkins, N. J.; Mumford, S. L.; Ye, A.; Schisterman, E. F.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Utilizing multiple biomarkers is increasingly common in epidemiology. However, the combined impact of correlated exposure measurement error, unmeasured confounding, interaction, and limits of detection (LODs) on inference for multiple biomarkers is unknown. We conducted data-driven simulations evaluating bias from correlated measurement error with varying reliability coefficients (R), odds ratios (ORs), levels of correlation between exposures and error, LODs, and interactions. Blood cadmium and lead levels in relation to anovulation served as the motivating example, based on findings from the BioCycle Study (2005–2007). For most scenarios, main-effect estimates for cadmium and lead with increasing levels of positively correlated measurement error created increasing downward or upward bias for OR > 1.00 and OR < 1.00, respectively, that was also a function of effect size. Some scenarios showed bias for cadmium away from the null. Results subject to LODs were similar. Bias for main and interaction effects ranged from −130% to 36% and from −144% to 84%, respectively. A closed-form continuous outcome case solution provides a useful tool for estimating the bias in logistic regression. Investigators should consider how measurement error and LODs may bias findings when examining biomarkers measured in the same medium...

‣ Are Network-Based Interventions a Useful Antiobesity Strategy? An Application of Simulation Models for Causal Inference in Epidemiology

El-Sayed, Abdulrahman M.; Seemann, Lars; Scarborough, Peter; Galea, Sandro
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Recent research suggests that social networks may present an avenue for intervention against obesity. By using a simulation model in which artificial individuals were nested in a social network, we assessed whether interventions targeting highly networked individuals could help reduce population obesity. We compared the effects of targeting antiobesity interventions at the most connected individuals in a network with those targeting individuals at random. We tested 2 interventions, the first “preventing” obesity among 10% of the population at simulation outset and the second “treating” obesity among 10% of the obese population yearly, each in 2 separate simulations. One simulation featured a literature-based parameter for the network spread of obesity, and the other featured an artificially high parameter. Interventions that targeted highly networked individuals did not outperform at-random interventions in simulations featuring the literature-based parameter. However, in simulations featuring the artificially high parameter, the targeted prevention intervention outperformed the at-random intervention, whereas the treatment intervention implemented at random outperformed the targeted treatment intervention. Results were qualitatively similar across network topologies and intervention scales. Although descriptive studies suggest that social networks influence the spread of obesity...

‣ Recapture or Precapture? Fallibility of Standard Capture-Recapture Methods in the Presence of Referrals Between Sources

Jones, Hayley E.; Hickman, Matthew; Welton, Nicky J.; De Angelis, Daniela; Harris, Ross J.; Ades, A. E.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Capture-recapture methods, largely developed in ecology, are now commonly used in epidemiology to adjust for incomplete registries and to estimate the size of difficult-to-reach populations such as problem drug users. Overlapping lists of individuals in the target population, taken from administrative data sources, are considered analogous to overlapping “captures” of animals. Log-linear models, incorporating interaction terms to account for dependencies between sources, are used to predict the number of unobserved individuals and, hence, the total population size. A standard assumption to ensure parameter identifiability is that the highest-order interaction term is 0. We demonstrate that, when individuals are referred directly between sources, this assumption will often be violated, and the standard modeling approach may lead to seriously biased estimates. We refer to such individuals as having been “precaptured,” rather than truly recaptured. Although sometimes an alternative identifiable log-linear model could accommodate the referral structure, this will not always be the case. Further, multiple plausible models may fit the data equally well but provide widely varying estimates of the population size. We demonstrate an alternative modeling approach...

‣ Identifying Postelimination Trends for the Introduction and Transmissibility of Measles in the United States

Blumberg, Seth; Enanoria, Wayne T. A.; Lloyd-Smith, James O.; Lietman, Thomas M.; Porco, Travis C.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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The continued elimination of measles requires accurate assessment of its epidemiology and a critical evaluation of how its incidence is changing with time. National surveillance of measles in the United States between 2001 and 2011 provides data on the number of measles introductions and the size of the resulting transmission chains. These data allow inference of the effective reproduction number, Reff, and the probability of an outbreak occurring. Our estimate of 0.52 (95% confidence interval: 0.44, 0.60) for Reff is smaller than prior results. Our findings are relatively insensitive to the possibility that as few as 75% of cases were detected. Although we confirm that measles remains eliminated, we identify an increasing trend in the number of measles cases with time. We show that this trend is likely attributable to an increase in the number of disease introductions rather than a change in the transmissibility of measles. However, we find that transmissibility may increase substantially if vaccine coverage drops by as little as 1%. Our general approach of characterizing the case burden of measles is applicable to the epidemiologic assessment of other weakly transmitting or vaccine-controlled pathogens that are either at risk of emerging or on the brink of elimination.

‣ Aprendizaje integrado de epidemiología y bioestadística en el Grado en Medicina: valoración de los estudiantes; Integrated learning of epidemiology and biostatistics in Medicine Degree : student assesment

Rubio Alonso, Margarita; Hernando Jerez, Asunción; Mohedano del Pozo, Rosa
Fonte: Universidade de Múrcia Publicador: Universidade de Múrcia
Tipo: Artigo de Revista Científica Formato: application/pdf
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Los objetivos fueron conocer la valoración de los alumnos de 2º de Medicina sobre la integración Epidemiología-Bioestadística y comparar su percepción a comienzo y final de curso. Se elaboraron dos cuestionarios con afirmaciones que los alumnos valoraron mediante una escala tipo Likert. Participaron 102 estudiantes. Para comparar los resultados a principio y final de curso se utilizó la prueba de rangos con signo de Wilcoxon. El 83% creía al finalizar el curso que comprendían la importancia de Epidemiología-Bioestadística en Medicina y les parecía interesante estudiarlas de forma integrada. Al inicio de curso, un 46,1% pensaba que la asignatura iba a ser interesante y al final este porcentaje fue 69,6%. Al inicio, el 69,6% veía la relación entre la Medicina y la Estadística y al final, el 83,3%. El 41% creía al inicio que iban a adquirir competencias fundamentales para el desempeño profesional y al final lo creía el 57,8%.; The aim of this study was to analyze how medical second-year students assessed the integration of Epidemiology and Biostatistics in a course, and to compare students´ perceptions at the onset and at the end of the academic year. Two questionnaires were administered to 102 medical students in order to explore the extent to which they agreed/disagreed with a number of statements using a Likert scale. A Wilcoxon signed-rank test was used to compare results. Upon completion of the course...

‣ Regression Calibration in Nutritional Epidemiology: Example of Fat Density and Total Energy in Relationship to Postmenopausal Breast Cancer

Prentice, Ross L.; Pettinger, Mary; Tinker, Lesley F.; Huang, Ying; Thomson, Cynthia A.; Johnson, Karen C.; Beasley, Jeannette; Anderson, Garnet; Shikany, James M.; Chlebowski, Rowan T.; Neuhouser, Marian L.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Regression calibration using biomarkers provides an attractive approach to strengthening nutritional epidemiology. We consider this approach to assessing the relationship of fat and total energy consumption with postmenopausal breast cancer. In analyses that included fat density data, biomarker-calibrated total energy was positively associated with postmenopausal breast cancer incidence in cohorts of the US Women's Health Initiative from 1994–2010. The estimated hazard ratio for a 20% increment in calibrated food frequency questionnaire (FFQ) energy was 1.22 (95% confidence interval (CI): 1.15, 1.30). This association was not evident without biomarker calibration, and it ceased to be apparent following control for body mass index (weight (kg)/height (m)2), suggesting that the association is mediated by body fat deposition over time. The hazard ratio for a corresponding 40% increment in FFQ fat density was 1.05 (95% CI: 1.00, 1.09). A stronger fat density association, with a hazard ratio of 1.19 (95% CI: 1.00, 1.41), emerged from analyses that used 4-day food records for dietary assessment. FFQ-based analyses were also carried out by using a second dietary assessment in place of the biomarker for calibration. This type of calibration did not correct for systematic bias in energy assessment...

‣ Assessment of Response Consistency and Respective Participant Profiles in the Internet-based NutriNet-Santé Cohort

Andreeva, Valentina A.; Galan, Pilar; Julia, Chantal; Castetbon, Katia; Kesse-Guyot, Emmanuelle; Hercberg, Serge
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Whereas the feasibility and effectiveness of Internet-based epidemiologic research have been established, methodological support for the quality of such data is still accumulating. We aimed to identify sociodemographic differences among members of a French cohort according to willingness to provide part of one's 15-digit national identification number (personal Social Security number (PSSN)) and to assess response consistency based on information reported on the sociodemographic questionnaire and that reflected in the PSSN. We studied 100,118 persons enrolled in an Internet-based prospective cohort study, the NutriNet-Santé Study, between 2009 and 2013. Persons aged 18 years or more who resided in France and had Internet access were eligible for enrollment. The sociodemographic profiles of participants with discordant data were compared against those of participants with concordant data via 2-sided polytomous logistic regression. In total, 84,442 participants (84.3%) provided the first 7 digits of their PSSN, and among them 5,141 (6.1%) had discordant data. Our multivariate analysis revealed differences by sex, age, education, and employment as regards response consistency patterns. The results support the quality of sociodemographic data obtained online from a large and diverse volunteer sample. The quantitative description of participant profiles according to response consistency patterns could inform future methodological work in e-epidemiology.

‣ Current practice of epidemiology in Africa: highlights of the 3rd conference of the African epidemiological association and 1st conference of the Cameroon society of epidemiology, Yaoundé, Cameroon, 2014

Nkwescheu, Armand Seraphin; Fokam, Joseph; Tchendjou, Patrice; Nji, Akindeh; Ngouakam, Hermann; Andre, Bita Fouda; Joelle, Sobngwi; Uzochukwu, Benjamin; Akinroye, Kingsley; Mbacham, Wilfred; Colizzi, Vittorio; Leke, Rose; Victora, Cesar
Fonte: The African Field Epidemiology Network Publicador: The African Field Epidemiology Network
Tipo: Artigo de Revista Científica
Publicado em 07/08/2015 Português
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As the study of disease occurrence and health indicators in human populations, Epidemiology is a dynamic field that evolves with time and geographical context. In order to update African health workers on current epidemiological practices and to draw awareness of early career epidemiologists on concepts and opportunities in the field, the 3rd African Epidemiology Association and the 1st Cameroon Society of Epidemiology Conference was organized in June 2-6, 2014 at the Yaoundé Mont Febe Hotel, in Cameroon. Under the theme«Practice of Epidemiology in Africa: Stakes, Challenges and Perspectives», the conference attracted close to five hundred guest and participants from all continents. The two main programs were the pre-conference course for capacity building of African Early Career epidemiologists, and the conference itself, providing a forum for scientific exchanges on recent epidemiological concepts, encouraging the use of epidemiological methods in studying large disease burden and neglected tropical diseases; and highlighting existing opportunities.

‣ “Toward a Clearer Definition of Confounding” Revisited With Directed Acyclic Graphs

Howards, Penelope P.; Schisterman, Enrique F.; Poole, Charles; Kaufman, Jay S.; Weinberg, Clarice R.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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In a 1993 paper (Am J Epidemiol. 1993;137(1):1–8), Weinberg considered whether a variable that is associated with the outcome and is affected by exposure but is not an intermediate variable between exposure and outcome should be considered a confounder in etiologic studies. As an example, she examined the common practice of adjusting for history of spontaneous abortion when estimating the effect of an exposure on the risk of spontaneous abortion. She showed algebraically that such an adjustment could substantially bias the results even though history of spontaneous abortion would meet some definitions of a confounder. Directed acyclic graphs (DAGs) were introduced into epidemiology several years later as a tool with which to identify confounders. The authors now revisit Weinberg's paper using DAGs to represent scenarios that arise from her original assumptions. DAG theory is consistent with Weinberg's finding that adjusting for history of spontaneous abortion introduces bias in her original scenario. In the authors' examples, treating history of spontaneous abortion as a confounder introduces bias if it is a descendant of the exposure and is associated with the outcome conditional on exposure or is a child of a collider on a relevant undirected path. Thoughtful DAG analyses require clear research questions but are easily modified for examining different causal assumptions that may affect confounder assessment.

‣ The Next PAGE in Understanding Complex Traits: Design for the Analysis of Population Architecture Using Genetics and Epidemiology (PAGE) Study

Matise, Tara C.; Ambite, Jose Luis; Buyske, Steven; Carlson, Christopher S.; Cole, Shelley A.; Crawford, Dana C.; Haiman, Christopher A.; Heiss, Gerardo; Kooperberg, Charles; Marchand, Loic Le; Manolio, Teri A.; North, Kari E.; Peters, Ulrike; Ritchie, Ma
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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Genetic studies have identified thousands of variants associated with complex traits. However, most association studies are limited to populations of European descent and a single phenotype. The Population Architecture using Genomics and Epidemiology (PAGE) Study was initiated in 2008 by the National Human Genome Research Institute to investigate the epidemiologic architecture of well-replicated genetic variants associated with complex diseases in several large, ethnically diverse population-based studies. Combining DNA samples and hundreds of phenotypes from multiple cohorts, PAGE is well-suited to address generalization of associations and variability of effects in diverse populations; identify genetic and environmental modifiers; evaluate disease subtypes, intermediate phenotypes, and biomarkers; and investigate associations with novel phenotypes. PAGE investigators harmonize phenotypes across studies where possible and perform coordinated cohort-specific analyses and meta-analyses. PAGE researchers are genotyping thousands of genetic variants in up to 121,000 DNA samples from African-American, white, Hispanic/Latino, Asian/Pacific Islander, and American Indian participants. Initial analyses will focus on single nucleotide polymorphisms (SNPs) associated with obesity...