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Association to Causation

Association to Causation. 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.

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Association to Causation

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  1. Association to Causation

  2. Clinical observations Available data Case-control studies Cohort studies Randomized trials Sequence of Studies

  3. Types of Associations • Real • Spurious

  4. DEFINITIONS • Observational study • Causation • Etiology • Association • Necessary • Sufficient Your Assignment: Define these terms as they apply to epidemiology.

  5. Koch and Causation • Postulates • Why study association? • Web of causation • Do we need a better way?

  6. 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

  7. Factors in Causation of Disease • Predisposing • Enabling • Precipitating • Reinforcing Your Assignment: Define these terms as they apply to epidemiology.

  8. Web of Causation

  9. 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

  10. Association • Deals with ………………. • Is concerned with ………. • Is the degree of …………. • Has to be scientifically proven ….. Your Assignment: fill in the blanks

  11. Degrees of Association • No association Direct association • No possibility for association • Possibly associated • Associated • Direct cause and effect

  12. 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

  13. Deriving Causal Inferences • Arriving at causation from association • For example, showing that Helicobacter pylori is directly linked to peptic ulcers

  14. Perspectives • Causation may be limited • Subject to modification • Perhaps more complex than realized • Sometimes not measureable • “Criteria” are really guidelines • may be subjective

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