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Module 2: Fundamentals of Epidemiology – Experimental Studies Transcript

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Module 2: Fundamentals of Epidemiology – Experimental Studies Transcript Slide 1: Introduction Hello, and welcome to module two: Fundamentals of Epidemiology. This presentation will focus on experimental studies. Experimental Studies Experimental Studies My name is Jeffery Bethel, assistant professor of Developed through the APTR Initiative to Enhance Prevention and Population HealthDeveloped Education through in collaborationthe APTR Initiative with the to BrodyEnhance School Prevention of Medicine and Populationat East epidemiology, East Carolina University, Brody CarolinaHealth UniversityEducation inwith collaboration funding from with the the Centers Brody forSchool Disease of Medicine Control andat East PreventionCarolina University with funding from the Centers for Disease Control and Prevention School of Medicine. Slide 2: Acknowledgements APTRAPTR wishes wishes to to acknowledge acknowledge the the following following individual individual that that developeddeveloped this this module: module: JeffreyJeffrey Bethel, Bethel, PhD PhD DepartmentDepartment of of Public Public Health Health BrodyBrody School School of of Medicine Medicine at at East East Carolina Carolina University University This education module is made possible through the Centers for Disease Control and Prevention (CDC) and the AssociationThis education for Prevention module is Teachingmade possible and Research through the(APTR) Centers Cooperative for Disease Agreement, Control and No. Prevention 5U50CD300860. (CDC) and The the module representsAssociation the for opinions Prevention of the Teaching author(s) and and Research does not (APTR) necessarily Cooperative represent Agreement, the views ofNo. the 5U50CD300860. Centers for Disease The module Controlrepresents and Prevention the opinions or of the the Association author(s) and for Preventiondoes not necessarily Teaching and represent Research. the views of the Centers for Disease Control and Prevention or the Association for Prevention Teaching and Research. Slide 3: Presentation Objectives There are four objectives in this presentation. 1.1. RecognizeRecognize use use of of experimental experimental studies studies as as an an epidemiologicepidemiologic study study design design They are: Recognize the use of experimental 2. Distinguish between types of experimental studies 2. Distinguish between types of experimental studies studies as an epidemiologic study design, 3.3. DescribeDescribe key key features features of of conducting conducting experimental experimental studiesstudies distinguish between types of experimental 4.4. RecognizeRecognize special special considerations considerations of of experimental experimental studiesstudies studies, describe key features of conducting experimental studies, and to recognize special considerations of experimental studies. Page 1 Module 2: Fundamentals of Epidemiology – Experimental Studies Transcript Slide 4: Analytic Study Designs In this presentation I will cover experimental ExperimentalExperimental studies studies (experimental) (experimental) ..ResearcherResearcherdeterminesdetermines who who is is exposed exposed studies, which are different than observational (treatments received) (treatments received) CohortCohort studies studies (observational) (observational) studies in that the researcher allocates Case-control studies (observational) Case-control studies (observational) treatment or exposure to study participants. CrossCross--sectionalsectional studies studies (observational) (observational) Observational studies are natural studies and are covered in another presentation. Slide 5: Experimental Studies The goal of public health as well as clinical GoalGoal of of public public health health and and clinical clinical medicine medicine is is to to modifymodify natural natural history history of of disease disease and and improve improve medicine is to essentially modify natural history morbiditymorbidity and and mortality mortality HowHow do do we we select select the the best best preventive preventive and and of disease to decrease morbidity and mortality. therapeutictherapeutic measures? measures? The question then becomes, how do we know CarryCarry out out studies studiestoto determine determine value value of of various various measuresmeasures which preventive and therapeutic measures are most effective to achieve this goal? To do that researchers carry out formal studies. Specifically experimental studies for the purposes of this presentation to determine the value of various measures. Slide 6: Study Design Hierarchy As you see in this diagram, experimental studies sit at the top of the hierarchy of epidemiologic study design and produce the most valid results but come at a very high cost. Smith, AH. The Epidemiologic Research Sequence. 1984 Smith, AH. The Epidemiologic Research Sequence. 1984 Page 2 Module 2: Fundamentals of Epidemiology – Experimental Studies Transcript Slide 7: Experimental Studies The reason experimental studies are at the top MostMost closely closely resemble resemble controlled controlled laboratory laboratory experimentsexperiments of the hierarchy is because they most closely GoldGold standard standard of of epidemiological epidemiological research research resemble controlled laboratory experiments. In HighHigh status status and and validity validity and and can can pick pick up up small small and and the controlled laboratory experiments modestmodest effects effects investigators regulate all the important aspects of the experimental conditions and allow the subjects to differ only for the purposes of testing the hypothesis. For example, if the investigator was testing the toxicity of a chemical in mice, he or she would include genetically similar or identical mice, assign mice to a test and control group, maintain the same physical environment for the mice, give them the same diet, and maintain the same daily schedule for the mice. That is so the investigator is in control of all aspects of the study. Experimental studies, for the purpose of epidemiologic study designs, are the gold standards of epidemiologic research. Their high status and validity enables them to pick up small and modest effects. Slide 8: Scurvy One of the first experimental studies of note JamesJames Lind Lind identified identified symptoms symptoms of of scurvy scurvy among among sailorssailors at at sea sea after after as as little little as as a a month month involves scurvy. James Lind originally identified ConductedConducted early early experimental experimental study study on on treatment treatment of of the symptoms of scurvy among sailors at sea scurvyscurvy in in mid mid--1700’s1700’s among among British British sailors sailors after as little as a month. The symptoms SmallSmall sample sample size size (6 (6 groups groups of of 2 2 ill ill sailors) sailors) included spongy and bleeding gums, bleeding GroupGroup eating eating oranges oranges and and lemons lemons were were fit fit for for duty duty in in 66 days days under the skin and extreme weakness. So Lind conducted an experimental study onboard a British ship in the mid-1700s in which he created six groups of two ill sailors each. He gave each group a different diet. He found that the group eating oranges, limes, and lemons, were fit for duty within six days. As a result of this experimental study, the British navy required limes and lime juice to be included in the diet of its sailors. Page 3 Module 2: Fundamentals of Epidemiology – Experimental Studies Transcript Slide 9: Potential Uses More contemporary uses of experimental studies EvaluateEvaluate new new drugs drugs and and other other treatments treatments for for diseasesdiseases include evaluating new drugs and other Evaluate new medical and health care technology Evaluate new medical and health care technology treatments for diseases, evaluating new medical EvaluateEvaluate new new screening screening programs programs or or techniques techniques and health care technology, evaluating new EvaluateEvaluate new new ways ways of of organizing organizing or or delivering delivering health health servicesservices (e.g. (e.g. home home v. v. hospital hospital care care following following myocardialmyocardial infarction) infarction) screening programs or techniques, or evaluating new ways of organizing or delivering health services. You could compare home versus hospital care following a myocardial infarction. Slide 10: Preventive V. Therapeutic Let’s get into some study design issues regarding PreventivePreventive .. DoesDoes prophylactic prophylactic agent agent given given to to healthy healthy or or high high-risk-risk experimental studies. Specifically, the various individualindividual to to prevent prevent disease? disease? ways to classify them. You can classify TherapeuticTherapeutic .. DoesDoes treatment treatment given given to to diseased diseased individual individual reduce reduce risk risk of of recurrence,recurrence, improve improve survival, survival, quality quality of of life? life? experimental studies based on their purpose as either preventive or therapeutic. In preventive studies we would ask the question: Does a prophylactic agent given to healthy or high-risk individuals prevent a disease? Whereas in a therapeutic study we would ask the question: Does the treatment given to diseased individuals reduce the risk of recurrence, improve survival or quality of life? Again, these types of studies are classified by their purpose; preventive or therapeutic. Page 4 Module 2:
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