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Identifiability, exchangeability and confounding revisitedEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In 1986 the International Journal of Epidemiology published "Identifiability, Exchangeability and Epidemiological Confounding". We review the article from the perspective of a quarter century after it was first drafted and relate it to subsequent developments on confounding, ignorability, and collapsibility.
Source: Epidemiologic Perspectives & Innovations - September 4, 2009 Category: Epidemiology Authors: Sander GreenlandJames Robins Source Type: journals

Update: Greenland and Robins (1986). Identifiability, exchangeability and epidemiological confounding.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We are pleased to publish an update to "Identifiabiliity, exchangeability and epidemiological confounding" (IEEC) by Sander Greenland and James Robins, originally published in 1986 in the International Journal of Epidemiology. This is the first in a series of updates to classic epidemiologic-methods papers that EP&I has commissioned.
Source: Epidemiologic Perspectives & Innovations - September 4, 2009 Category: Epidemiology Authors: George Maldonado Source Type: journals

The role of causal criteria in causal inferences: Bradford Hill's "aspects of association"Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
As noted by Wesley Salmon and many others, causal concepts are ubiquitous in every branch of theoretical science, in the practical disciplines and in everyday life. In the theoretical and practical sciences especially, people often base claims about causal relations on applications of statistical methods to data. However, the source and type of data place important constraints on the choice of statistical methods as well as on the warrant attributed to the causal claims based on the use of such methods. For example, much of the data used by people interested in making causal claims come from non-experimental, observational...
Source: Epidemiologic Perspectives & Innovations - June 17, 2009 Category: Epidemiology Authors: Andrew Ward Source Type: journals

Trend tests for the evaluation of exposure-response relationships in epidemiological exposure studiesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
One possibility for the statistical evaluation of trends in epidemiological exposure studies is the use of a trend test for data organized in a 2 by k contingency table. Commonly, the exposed data are naturally grouped or continuous exposure data can be appropriately categorized. The trend test should be sensitive to any shape of the exposure-response relationship. Commonly, a global trend test only leads to a decision of whether there is a trend or not. Once the existence of a trend is shown it is important to identify the likely shape of the exposure-response relationship. We introduce a best contrast approach and an alt...
Source: Epidemiologic Perspectives & Innovations - March 6, 2009 Category: Epidemiology Authors: Ludwig A Hothorn, Michael Vaeth and Torsten Hothorn Source Type: journals

Using the National Health Interview Survey to understand and address the impact of tobacco in the United States: past perspectives and future considerationsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusion: NHIS data provide information that can be useful to both practitioners and researchers. It is important to explore new and creative ways to best use these data and to address the full range of salient tobacco-related topics. Doing so will better inform future tobacco control research and programs.
Source: Epidemiologic Perspectives & Innovations - December 4, 2008 Category: Epidemiology Authors: Cathy L. Backinger, Deirdre Lawrence, Judith Swan, Deborah M. Winn, Nancy Breen, Anne Hartman, Rachel Grana, David Tran and Samantha Farrell Source Type: journals

Using the National Health Interview Survey to understand and address the impact of tobacco in the United States: past perspectives and future considerationsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusion: NHIS data provide information that can be useful to both practitioners and researchers. It is important to explore new and creative ways to best use these data and to address the full range of salient tobacco-related topics. Doing so will better inform future tobacco control research and programs.
Source: Epidemiologic Perspectives & Innovations - December 4, 2008 Category: Epidemiology Authors: Cathy L Backinger, Deirdre Lawrence, Judith Swan, Deborah M Winn, Nancy Breen, Anne Hartman, Rachel Grana, David Tran and Samantha Farrell Source Type: journals

Methods for stratification of person-time and events - a prerequisite for Poisson regression and SIR estimationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Many epidemiological methods for analysing follow-up studies require the calculation of rates based on accumulating person-time and events, stratified by various factors. Managing this stratification and accumulation is often the most difficult aspect of this type of analysis. We provide a tutorial on accumulating person-time and events, stratified by various factors i.e. creating event-time tables. We show how to efficiently generate event-time tables for many different outcomes simultaneously. We also provide a new vocabulary to characterise and differentiate time-varying factors. The tutorial is focused on using a SAS m...
Source: Epidemiologic Perspectives & Innovations - November 14, 2008 Category: Epidemiology Authors: Klaus Rostgaard Source Type: journals

Case-case analysis of enteric diseases with routine surveillance data: Potential use and example resultsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusion: Case-case analyses of enteric diseases using routine surveillance data might be a useful low-cost means to study trends in enteric disease sources and inform control measures. If used, it should probably supplement rather than replace outbreak investigations and case-control studies. Furthermore, it could be enhanced by utilising high quality individual-level data provided by nationally-representative sentinel sites for enteric disease surveillance.
Source: Epidemiologic Perspectives & Innovations - October 31, 2008 Category: Epidemiology Authors: Nick Wilson, Michael Baker, Richard Edwards and Greg Simmons Source Type: journals

Partitioning the population attributable fraction for a sequential chain of effectsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusions: Combined with simple, unadjusted PAF estimates and an aggregate PAF based on all risk factors under consideration, the sequentially partitioned PAF provides valuable additional information regarding the process through which population rates of a disorder may be impacted. In addition, the approach can also be used to statistically control for confounding by other variables, while avoiding the potential pitfalls of attempting to separately differentiate direct and indirect effects.
Source: Epidemiologic Perspectives & Innovations - October 2, 2008 Category: Epidemiology Authors: Craig A Mason and Shihfen Tu Source Type: journals

Flexible two-phase studies for rare exposures: feasibility, planning and efficiency issues of a new variantEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The two-phase design consists of an initial (Phase One) study with known disease status and inexpensive covariate information. Within this initial study one selects a subsample on which to collect detailed covariate data. Two-phase studies have been shown to be efficient compared to standard case-control designs. However, potential problems arise if one cannot assure minimum sample sizes in the rarest categories or if recontact of subjects is difficult. In the case of a rare exposure with an inexpensive proxy, the authors propose the flexible two-phase design for which there is a single time of contact at which a decision...
Source: Epidemiologic Perspectives & Innovations - October 1, 2008 Category: Epidemiology Authors: Pascal Wild, Nadine Andrieu, Alisa M Goldstein and Walter Schill Source Type: journals

Factors related to the frequency of citation of epidemiologic publicationsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusion: Journal and country appear to be the factors most strongly associated with frequency of citation. In particular, highly-cited articles are predominantly published in high-impact, high-circulation journals. The factors, however, differ somewhat depending on the area of research the journals represent. Among CAD prevention articles, for example, topic is also an important predictor of citation whereas the same is not true for articles addressing child injury prevention.
Source: Epidemiologic Perspectives & Innovations - February 26, 2008 Category: Epidemiology Authors: Kristian B Filion and I B Pless Source Type: journals

Should adjustment for covariates be used in prevalence estimations?Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusions: Adjustment for covariates will not result in more accurate prevalence estimator when ratio of male to female prevalences is close to one, sample size is small and risk factor prevalence is low. For example, when reporting smoking prevalence based on simple random sampling, gender adjustment is recommended only when sample size is greater than 200.
Source: Epidemiologic Perspectives & Innovations - January 25, 2008 Category: Epidemiology Authors: Wenjun Li, Edward J. Stanek and Elizabeth R. Berton-Johnson Source Type: journals

Feasibility of an automated telephone survey to enable prospective monitoring of subjects whose confidentiality is paramount: a four-week cohort study of partner violence recurrence after Emergency Department dischargeEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusion: Approximately three of every four subjects participated in follow-up after ED discharge, and approximately two of every four subjects completed all follow-up reports, suggesting the method of an automated telephone survey and wireless incentive delivery system makes it feasible to study IPV prospectively among discharged patients. That finding, along with evidence that IPV recurrence risk is high, suggests the protocol tested is warranted for use conducting full-scale studies of IPV. The protocol could benefit efforts to study other outcomes, especially when patient confidentiality is paramount for their safety.
Source: Epidemiologic Perspectives & Innovations - January 7, 2008 Category: Epidemiology Authors: Douglas J Wiebe, Brendan G Carr, Elizabeth M Datner, Michael R Elliott and Therese S Richmond Source Type: journals

Case-cohort design in practice -- experiences from the MORGAM ProjectEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
When carefully planned and analysed, the case-cohort design is a powerful choice for follow-up studies with multiple event types of interest. While the literature is rich with analysis methods for case-cohort data, little is written about the designing of a case-cohort study. Our experiences in designing, coordinating and analysing the MORGAM case-cohort study are potentially useful for other studies with similar characteristics. The motivation for using the case-cohort design in the MORGAM genetic study is discussed and issues relevant to its planning and analysis are studied. We propose solutions for appending the earlie...
Source: Epidemiologic Perspectives & Innovations - December 4, 2007 Category: Epidemiology Authors: Sangita Kulathinal, Juha Karvanen, Olli Saarela, Kari Kuulasmaa and for the MORGAM Project Source Type: journals

Older adults' perspectives on key domains of childhood social and economic experiences and opportunities: a first step to creating a multidimensional measureEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusions: These domains of childhood social and economic circumstances add breadth and depth to conventional conceptualization of childhood SES. When the domains are translated into a measurement tool, it will allow for the possibility of classifying people along multiple dimensions, such as from a low economic circumstance with high levels of adult support.
Source: Epidemiologic Perspectives & Innovations - November 6, 2007 Category: Epidemiology Authors: Irene H Yen, Anita L Stewart, Teresa Scherzer and Eliseo J Perez-Stable Source Type: journals

Warning: Anti-tobacco activism may be hazardous to epidemiologic scienceEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This commentary accompanies two articles submitted to Epidemiologic Perspectives & Innovations in response to a call for papers about threats to epidemiology or epidemiologists from organized political interests. Contrary to our expectations, we received no submissions that described threats from industry or government; all were about threats from anti-tobacco activists. The two we published, by James E. Enstrom and Michael Siegel, both deal with the issue of environmental tobacco smoke. This commentary adds a third story of attacks on legitimate science by anti-tobacco activists, the author's own experience. These stories...
Source: Epidemiologic Perspectives & Innovations - October 22, 2007 Category: Epidemiology Authors: Carl V Phillips Source Type: journals

Is the tobacco control movement misrepresenting the acute cardiovascular health effects of secondhand smoke exposure? An analysis of the scientific evidence and commentary on the implications for tobacco control and public health practiceEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
While chronic exposure to secondhand smoke has been well recognized as a cause of heart disease in nonsmokers, there has been recent speculation about the potential acute cardiovascular effects of transient exposure to secondhand smoke among nonsmokers; in particular, the possibility that such exposure could increase the risk of acute myocardial infarction even in an otherwise healthy nonsmoker. This paper reviews the claims being made by a number of anti-smoking and public health groups regarding the acute cardiovascular effects of secondhand smoke exposure among otherwise healthy adults, analyzes the validity of these cl...
Source: Epidemiologic Perspectives & Innovations - October 10, 2007 Category: Epidemiology Authors: Michael Siegel Source Type: journals

Defending legitimate epidemiologic research: combating Lysenko pseudoscienceEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This analysis presents a detailed defense of my epidemiologic research in the May 17, 2003 British Medical Journal that found no significant relationship between environmental tobacco smoke (ETS) and tobacco-related mortality. In order to defend the honesty and scientific integrity of my research, I have identified and addressed in a detailed manner several unethical and erroneous attacks on this research. Specifically, I have demonstrated that this research is not "fatally flawed," that I have not made "inappropriate use" of the underlying database, and that my findings agree with other United States results on this relat...
Source: Epidemiologic Perspectives & Innovations - October 10, 2007 Category: Epidemiology Authors: James E Enstrom Source Type: journals

Changing population characteristics, effect-measure modification, and cancer risk factor identificationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In conclusion, as population characteristics change over time, these changes may have an influence on relative risk estimates for colon cancer for other exposures because of effect-measure modification. The impact of population changes on comparability between epidemiologic studies can be kept to a minimum if investigators assess exposure-disease associations within strata of other exposures, and present results in a manner that allows comparisons across studies. Effect-measure modification is an important component of data analysis that should be evaluated to obtain a complete understanding of disease etiology.
Source: Epidemiologic Perspectives & Innovations - October 1, 2007 Category: Epidemiology Authors: Martha L. Slattery, Maureen A. Murtaugh, Charles Quesenberry, Bette J. Caan, Sandra Edwards and Carol Sweeney Source Type: journals

Estimating uncertainty in observational studies of associations between continuous variables: example of methylmercury and neuropsychological testing in childrenEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusions: Based on our sensitivity analysis results, it is not possible to draw definitive conclusions about the presence or absence of neurodevelopmental effects due to in utero methylmercury exposure at levels reported in the FIS and SCDS.
Source: Epidemiologic Perspectives & Innovations - September 26, 2007 Category: Epidemiology Authors: Michael Goodman, Leila M Barraj, Pamela J Mink, Nicole L Britton, Janice W Yager, William D Flanders and Michael A Kelsh Source Type: journals

Translational methods in biostatistics: linear mixed effect regression models of alcohol consumption and HIV disease progression over timeEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We describe a linear mixed effects regression framework that accounts for the clustering of longitudinal data and that can be fit using standard statistical software. We apply the linear mixed effects model to a previously published dataset of HIV infected individuals with a history of alcohol problems who are receiving HAART (n=197). The researchers were interested in determining the effect of alcohol use on HIV disease progression over time. Fitting a linear mixed effects multiple regression model with a random intercept and random slope for each subject accounts for the association of observations within subjects and yi...
Source: Epidemiologic Perspectives & Innovations - September 19, 2007 Category: Epidemiology Authors: Mariel M Finucane, Jeffrey H Samet and Nicholas J Horton Source Type: journals

Consent for long-term storage of blood samples by Indigenous Australian research participants: the DRUID Study experienceEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusions: These data show that consent for blood storage among these research participants was neither rare nor universal. It was associated with some socio-demographic/cultural factors but not with blood biochemistry. Decisions about requesting or giving consent for storage and later use of tissue samples must recognize a number of important, and potentially competing, ethical and logistical considerations.
Source: Epidemiologic Perspectives & Innovations - September 7, 2007 Category: Epidemiology Authors: Joan Cunningham and Terry Dunbar Source Type: journals

Mortality ascertainment of participants in the National Wilms Tumor Study using the National Death Index: comparison of active and passive follow-up resultsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Long term studies of childhood cancer survivors are hampered by difficulties in tracking young adult participants. After performing a National Death Index (NDI) search we sought to identify which factors best predicted a match among known decedents from the National Wilms Tumor Study (NWTS) and to determine if record linkage could substitute for missing follow-up in a cohort of NWTS survivors. To our knowledge, this is the first study to compare passive mortality follow-up using the NDI to active follow-up of a childhood and young adult population. Records for 984 known decedents and 3,406 subjects whose January 1, 2002 vi...
Source: Epidemiologic Perspectives & Innovations - July 2, 2007 Category: Epidemiology Authors: Cecilia A Cotton, Susan Peterson, Patricia A Norkool and Norman E Breslow Source Type: journals

Power for tests of interaction: effect of raising the Type I error rateEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusion: Relaxing the Type I error rate did not usefully improve the power for tests of interaction in many of the scenarios studied. In many studies, the small power gains obtained by raising the Type I error will be more than offset by the disadvantage of increased "false positives". I recommend investigators should not routinely raise the Type I error rate when assessing tests of interaction.
Source: Epidemiologic Perspectives & Innovations - June 19, 2007 Category: Epidemiology Authors: Stephen W Marshall Source Type: journals

Lessons from previous predictions of HIV/AIDS in the United States and Japan: Epidemiologic models and policy formulationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This paper critically discusses two previous studies concerned with predictions of HIV/AIDS in the United States and Japan during the early 1990s. Although the study in the US applied a historical theory, assuming normal distribution for the epidemic curve, the underlying infection process was not taken into account. In the Japan case, the true HIV incidence was estimated using the coverage ratio of previously diagnosed/undiagnosed HIV infections among AIDS cases, the assumptions of which were not supported by a firm theoretical understanding. At least partly because of failure to account for underlying mechanisms of the d...
Source: Epidemiologic Perspectives & Innovations - June 13, 2007 Category: Epidemiology Authors: Hiroshi Nishiura Source Type: journals

Utilization of routinely collected administrative data in monitoring the incidence of aging dependent hip fractureEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In conclusion, Finnish administrative data makes it possible to derive data for rather detailed population level risk factor stratification. Certain limitations of register-based data can be partly avoided by synthesizing data-sensitive methodological solutions during the analysis process.
Source: Epidemiologic Perspectives & Innovations - June 7, 2007 Category: Epidemiology Authors: Reijo Sund Source Type: journals

Applying the compound Poisson process model to the reporting of injury-related mortality ratesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Injury-related mortality rate estimates are often analyzed under the assumption that case counts follow a Poisson distribution. Certain types of injury incidents occasionally involve multiple fatalities, however, resulting in dependencies between cases that are not reflected in the simple Poisson model and which can affect even basic statistical analyses. This paper explores the compound Poisson process model as an alternative, emphasizing adjustments to some commonly used interval estimators for population-based rates and rate ratios. The adjusted estimators involve relatively simple closed-form computations, which in the...
Source: Epidemiologic Perspectives & Innovations - February 16, 2007 Category: Epidemiology Authors: Scott R Kegler Source Type: journals

Generalizability in two clinical trials of Lyme diseaseEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusions: The Klempner et al. trials are assumed to be internally valid based on a Randomized Control Trial (RCT) design. However, this review argues that the trials have limited generalizability beyond the select group of patients with characteristics like those in the trial. Applying the findings to target populations with characteristics that differ from those included in these trials is inappropriate and may limit options for chronic Lyme disease patients who might benefit from antibiotic treatment.
Source: Epidemiologic Perspectives & Innovations - October 17, 2006 Category: Epidemiology Authors: Daniel J Cameron Source Type: journals

New patient-oriented summary measure of net total gain in certainty for dichotomous diagnostic testsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusion: PSI provides more information than J and the predictive values, making it more appropriate in a clinical setting.
Source: Epidemiologic Perspectives & Innovations - October 5, 2006 Category: Epidemiology Authors: Shai Linn and Peter D Grunau Source Type: journals

Causal thinking and causal language in epidemiology: a cause by any other name is still a causeEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
I have great sympathy with the thoughts of Lipton and Odegaard - the assessment and communication of "causal" associations is a source of continual frustration for epidemiologists. The authors' lucid account of the use of causal language in epidemiology can essentially (if rather unflatteringly) be simplified to the following: it is impossible to prove that X causes Y; the statement "Smoking causes lung cancer" is thus no more informative than the statement "Smoking two packs a day for N years increases your risk of lung cancer ten-fold". In fact, it is less informative and even misleading. The authors argue that such caus...
Source: Epidemiologic Perspectives & Innovations - June 6, 2006 Category: Epidemiology Authors: Clarence C Tam Source Type: journals

Causal thinking and causal language in epidemiology: a cause by any other name is still a cause response to Lipton and OdegaardEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
I have great sympathy with the thoughts of Lipton and Odegaard - the assessment and communication of "causal" associations is a source of continual frustration for epidemiologists. The authors' lucid account of the use of causal language in epidemiology can essentially (if rather unflatteringly) be simplified to the following: it is impossible to prove that X causes Y; the statement "Smoking causes lung cancer" is thus no more informative than the statement "Smoking two packs a day for N years increases your risk of lung cancer ten-fold". In fact, it is less informative and even misleading. The authors argue that such caus...
Source: Epidemiologic Perspectives & Innovations - June 6, 2006 Category: Epidemiology Authors: Clarence C Tam Source Type: journals

Causal thinking and causal language in epidemiology: a cause by any other name is still a cause: response to Lipton and OdegaardEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
I have great sympathy with the thoughts of Lipton and Odegaard - the assessment and communication of "causal" associations is a source of continual frustration for epidemiologists. The authors' lucid account of the use of causal language in epidemiology can essentially (if rather unflatteringly) be simplified to the following: it is impossible to prove that X causes Y; the statement "Smoking causes lung cancer" is thus no more informative than the statement "Smoking two packs a day for N years increases your risk of lung cancer ten-fold". In fact, it is less informative and even misleading. The authors argue that such caus...
Source: Epidemiologic Perspectives & Innovations - June 6, 2006 Category: Epidemiology Authors: Clarence C Tam Source Type: journals

Causal thinking and causal language in epidemiology: a cause by any other name is still a cause: response to Lipton and ØdegaardEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
I have great sympathy with the thoughts of Lipton and Odegaard - the assessment and communication of "causal" associations is a source of continual frustration for epidemiologists. The authors' lucid account of the use of causal language in epidemiology can essentially (if rather unflatteringly) be simplified to the following: it is impossible to prove that X causes Y; the statement "Smoking causes lung cancer" is thus no more informative than the statement "Smoking two packs a day for N years increases your risk of lung cancer ten-fold". In fact, it is less informative and even misleading. The authors argue that such caus...
Source: Epidemiologic Perspectives & Innovations - June 6, 2006 Category: Epidemiology Authors: Clarence C Tam Source Type: journals

Exposure assessment in investigations of waterborne illness: a quantitative estimate of measurement errorEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Conclusions: This study demonstrated substantial misclassification errors associated with a surrogate measure commonly used in studies of drinking water disinfection byproducts. Further, the limited accuracy of two surrogate measures of an individual's home water source heeds caution in their use in exposure classification methodology. While these surrogates are inexpensive and convenient, they should not be substituted for direct collection of accurate data pertaining to the subjects' waterborne disease exposure. In instances where such surrogates must be used, estimation of the misclassification and its subsequent effect...
Source: Epidemiologic Perspectives & Innovations - May 26, 2006 Category: Epidemiology Authors: Andria Q Jones, Catherine E Dewey, Kathryn Dore, Shannon E Majowicz, Scott A McEwen and David Waltner-Toews Source Type: journals

Measuring additive interaction using odds ratiosEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Interaction measured on the additive scale has been argued to be better correlated with biologic interaction than when measured on the multiplicative scale. Measures of interaction on the additive scale have been developed using risk ratios. However, in studies that use odds ratios as the sole measure of effect, the calculation of these measures of additive interaction is usually performed by directly substituting odds ratios for risk ratios. Yet assessing additive interaction based on replacing risk ratios by odds ratios in formulas that were derived using the former may be erroneous. In this paper, we evaluate the extent...
Source: Epidemiologic Perspectives & Innovations - April 18, 2006 Category: Epidemiology Authors: Linda Kalilani and Julius Atashili Source Type: journals

The North West Adelaide Health Study: detailed methods and baseline segmentation of a cohort for selected chronic diseasesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The North West Adelaide Health Study is a population-based biomedical cohort study investigating the prevalence of a number of chronic conditions and health-related risk factors along a continuum. This methodology may assist with evidence-based decisions for health policy makers and planners, and inform health professionals who are involved in chronic disease prevention and management, by providing a better description of people at risk of developing or already diagnosed with selected chronic conditions for more accurate targeting groups for health gain and improved health outcomes. Longitudinal data will provide informati...
Source: Epidemiologic Perspectives & Innovations - April 12, 2006 Category: Epidemiology Authors: Janet F Grant, Catherine R Chittleborough, Anne W Taylor, Eleonora Dal Grande, David H Wilson, Patrick J Phillips, Robert J Adams, Julianne Cheek, Kay Price, Tiffany Gill, Richard E Ruffin and the North West Adelaide Health Study Team Source Type: journals

A demonstration of modeling count data with an application to physical activityEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Counting outcomes such as days of physical activity or servings of fruits and vegetables often have distributions that are highly skewed toward the right with a preponderance of zeros, posing analytical challenges. This paper demonstrates how such outcomes may be analyzed with several modifications to Poisson regression.Five regression models 1) Poisson, 2) overdispersed Poisson, 3) negative binomial, 4) zero-inflated Poisson (ZIP), and 5) zero-inflated negative binomial (ZINB) are fitted to data assessing predictors of vigorous physical activity (VPA) among Latina women. The models are described, and analytical and graphi...
Source: Epidemiologic Perspectives & Innovations - March 21, 2006 Category: Epidemiology Authors: Donald J Slymen, Guadalupe X Ayala, Elva M Arredondo and John P Elder Source Type: journals

Causal analysis of case-control dataEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In a series of papers, Robins and colleagues describe inverse probability of treatment weighted (IPTW) estimation in marginal structural models (MSMs), a method of causal analysis of longitudinal data based on counterfactual principles. This family of statistical techniques is similar in concept to weighting of survey data, except that the weights are estimated using study data rather than defined so as to reflect sampling design and post-stratification to an external population. Several decades ago Miettinen described an elementary method of causal analysis of case-control data based on indirect standardization. In this p...
Source: Epidemiologic Perspectives & Innovations - January 27, 2006 Category: Epidemiology Authors: Stephen C Newman Source Type: journals

Web-based data collection: detailed methods of a questionnaire and data gathering toolEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
There have been dramatic advances in the development of web-based data collection instruments. This paper outlines a systematic web-based approach to facilitate this process through locally developed code and to describe the results of using this process after two years of data collection. We provide a detailed example of a web-based method that we developed for a study in Starr County, Texas, assessing high school students' work and health status. This web-based application includes data instrument design, data entry and management, and data tables needed to store the results that attempt to maximize the advantages of thi...
Source: Epidemiologic Perspectives & Innovations - January 4, 2006 Category: Epidemiology Authors: Charles J Cooper, Sharon P Cooper, Deborah J del Junco, Eva M Shipp, Ryan Whitworth and Sara R Cooper Source Type: journals

Choosing an appropriate bacterial typing technique for epidemiologic studiesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A wide variety of bacterial typing systems are currently in use that vary greatly with respect to the effort required, cost, reliability and ability to discriminate between bacterial strains. No one technique is optimal for all forms of investigation. We discuss the desired level of discrimination and need for a biologic basis for grouping strains of apparently different types when using bacterial typing techniques for different epidemiologic applications: 1) confirming epidemiologic linkage in outbreak investigations, 2) generating hypotheses about epidemiologic relationships between bacterial strains in the absence of ep...
Source: Epidemiologic Perspectives & Innovations - November 25, 2005 Category: Epidemiology Authors: Betsy Foxman, Lixin Zhang, James S Koopman, Shannon D Manning and Carl F Marrs Source Type: journals

An easy approach to the Robins-Breslow-Greenland variance estimatorEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This article provides an accessible derivation which demonstrates the link between the Robins-Breslow-Greenland estimate and the familiar Woolf estimate for the variance of the log odds ratio, and which could easily be included in Masters level courses in epidemiology. The relationships to the unconditional and conditional maximum likelihood estimates are also reviewed.
Source: Epidemiologic Perspectives & Innovations - September 26, 2005 Category: Epidemiology Authors: Paul Silcocks Source Type: journals

Causal thinking and causal language in epidemiology: it's in the detailsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Although epidemiology is necessarily involved with elucidating causal processes, we argue that there is little practical need, having described an epidemiological result, to then explicitly label it as causal (or not). Doing so is a convention which obscures the valuable core work of epidemiology as an important constituent of public health practice. We discuss another approach which emphasizes the public health "use value" of research findings in regard to prediction and intervention independent from explicit metaphysical causal claims. Examples are drawn from smoking and lung cancer, with particular focus on the original...
Source: Epidemiologic Perspectives & Innovations - July 29, 2005 Category: Epidemiology Authors: Robert Lipton and Terje Ødegaard Source Type: journals

Reporting incidence from a surveillance system with an operational case definition of unknown predictive value positiveEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
When reporting incidence rate estimates for relatively rare health conditions, associated case counts are often assumed to follow a Poisson distribution. Case counts obtained from large-scale electronic surveillance systems are often inflated by the presence of false positives, however, and adjusted case counts based on the results of a validation sample will have variances which are hyper-Poisson. This paper presents a simple method for constructing interval estimates for incidence rates based on case counts that are adjusted downward using an estimate of the predictive value positive of the surveillance case definition.
Source: Epidemiologic Perspectives & Innovations - July 20, 2005 Category: Epidemiology Authors: Scott R Kegler Source Type: journals

Teaching: the role of active manipulation of three-dimensional scatter plots in understanding the concept of confoundingEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In teaching epidemiology, confounding is a difficult topic. The authors designed active learning objects (LO) based on manipulable three-dimensional (3D) plots to facilitate understanding of confounding. The 3D LOs help illustrate of how confounding can occur, how it generates bias and how to adjust for it. For the development of the LOs, guidelines were formulated based on epidemiology and theories of instructional design. These included integrating the conceptual and empirical aspects: the causal relationships believed to be operating in the study population (conceptual aspect) and data-oriented associations (empirical a...
Source: Epidemiologic Perspectives & Innovations - June 14, 2005 Category: Epidemiology Authors: Cora MC Busstra, Rob Hartog and Pieter van 't Veer Source Type: journals