Lecture 02c.pptx

Lecture 02c.pptx - Lecture 2 - Part III Introduction to...

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Introduction to Study Designs Michaela Smith January 21, 2010 Lecture 2 - Part III
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Topics Contrast between experimental and observational studies Contrast between descriptive and analytic studies Overview of main epidemiologic study designs
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Categories of Epidemiologic Studies Epidemiologic Studies Observational Experimental Descriptive Analytic (Case reports) (Case series) Prospective cohort Retrospective cohort Case-control Randomized controlled trials Community trials Ecologic Cross-sectional
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Exposures and Outcomes ‘exposure’: any factor that might influence health , positively or negatively Conventional: virus, chemicals, but also: personal characteristics such as sex, age, skin colour, etc. ‘outcome’: most often disease, but can be any type of health status E.g. smoking status, vaccination status, pregnancy, etc.
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Experimental Studies Experimental studies test hypotheses between specific exposures and outcomes Investigator has direct control over the study conditions (i.e. who is exposed and who isn’t) Assignment of the exposure = key aspect usually through randomization Can only be conducted when ethically feasible
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Observational Studies Observational studies may also test hypotheses between specific exposures and outcomes Investigator does not control the study conditions Investigator collects information about exposure(s) and outcome(s) to identify areas for further study or to draw inferences about etiology* Without randomization, alternate explanations for any association that is observed need to be considered
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Categories of Epidemiologic Studies Epidemiologic Studies Observational Experimental Descriptive Analytic Case reports Case series Prospective cohort Retrospective cohort Case-control Randomized controlled trials Community trials Ecologic Cross-sectional
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Descriptive Observational Studies Research that describes the occurrence of an exposure and/or outcome in a population Often used to look for patterns of disease by person, place or time variables Answer the questions: Who? Where? When? May suggest a direction to explore Why? but cannot provide an answer due to lack of an explicit comparison group Example: In the 1990s spinal fractures on farms were increasing and other farm injuries were declining Led to inquiries about role of changing farm practices Found that new baling methods were responsible
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Categories of Epidemiologic Studies Epidemiologic Studies Observational Experimental Descriptive Analytic Case reports Case series Prospective cohort Retrospective cohort Case-control Randomized controlled trials Community trials Ecologic Cross-sectional
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Analytic Observational Studies In contrast to descriptive studies, analytic studies incorporate a formal comparison group Go further to incorporate analysis of associations between exposures and outcomes Main tools for identifying the causes of disease May be used to Test specific etiologic hypotheses
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This note was uploaded on 02/23/2012 for the course EPID 301 taught by Professor Richardson&aronson during the Spring '09 term at Queens University.

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Lecture 02c.pptx - Lecture 2 - Part III Introduction to...

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