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Explore the fundamental concepts of association and causation in epidemiology, from observational studies to randomized trials, defining key terms such as causation and etiology. Learn about Koch's postulates, criteria for causation, guidelines for judging causal associations, degrees of association, and deriving causal inferences. Analyze real-world examples like smoking and lung cancer for a better understanding of epidemiological associations.
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Clinical observations Available data Case-control studies Cohort studies Randomized trials Sequence of Studies
Types of Associations • Real • Spurious
DEFINITIONS • Observational study • Causation • Etiology • Association • Necessary • Sufficient Your Assignment: Define these terms as they apply to epidemiology.
Koch and Causation • Postulates • Why study association? • Web of causation • Do we need a better way?
Cause distributed at same level Incidence much higher in exposed population Exposure more frequent Disease should follow exposure Dose dependent Expected response Association should be the same Other cause-effect ruled out Control results in decreased disease Modification of host results in decrease Human vol. always + Findings should make sense Twelve Criteria for Causation
Factors in Causation of Disease • Predisposing • Enabling • Precipitating • Reinforcing Your Assignment: Define these terms as they apply to epidemiology.
Are Associations Always Connected to the Disease? NO, BUT ………………………….. • Cigarette smoking and lung cancer • Age and prostate cancer • Car accidents and alcohol • Tribal customs and kuru • Agriculture and antibiotic resistance
Association • Deals with ………………. • Is concerned with ………. • Is the degree of …………. • Has to be scientifically proven ….. Your Assignment: fill in the blanks
Degrees of Association • No association Direct association • No possibility for association • Possibly associated • Associated • Direct cause and effect
Guidelines for Judging Whether An Association Is Causal • Temporal relationship • Strength of the association • Dose-response relationship • Replication of the findings • Biologic plausibility • Consideration of alternate explanations • Specificity of the association • Consistency with other knowledge
Deriving Causal Inferences • Arriving at causation from association • For example, showing that Helicobacter pylori is directly linked to peptic ulcers
Perspectives • Causation may be limited • Subject to modification • Perhaps more complex than realized • Sometimes not measureable • “Criteria” are really guidelines • may be subjective