Association to Causation. Sequence of Studies Clinical observations Available data Case-control...
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Transcript of Association to Causation. Sequence of Studies Clinical observations Available data Case-control...
![Page 1: Association to Causation. Sequence of Studies Clinical observations Available data Case-control studies Cohort studies Randomized trials.](https://reader033.fdocuments.in/reader033/viewer/2022052401/56649d615503460f94a4325c/html5/thumbnails/1.jpg)
Association to Causation
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Sequence of Studies
Clinical observations
Available data
Case-control studies
Cohort studies
Randomized trials
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Types of Associations
• Real
• Spurious
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DEFINITIONS
• Observational study
• Causation
• Association
• Necessary
• Sufficient
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Koch and Causation
• Postulates
• Why study association
• Web of causation
• Do we need a better way
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Twelve Criteria for Causation
• 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
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Factors in Causation of Disease
• Predisposing
• Enabling
• Precipitating
• Reinforcing
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Web of Causation
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Are Associations Always Connected to the Disease?
NO, BUT …………………………..Cigarette smoking and lung cancerAge and prostate cancerCar accidents and alcoholTribal customs and kuruAgriculture and antibiotic resistance
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Association
• Deals with ……………….
• Is concerned with ……….
• Is the degree of ………….
• Has to be scientifically proven …..
Your Assignment: fill in the blanks
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Degrees of Association
• No assoc. Direct assoc.No possibility for associationPossibly associatedAssociatedDirect cause and effect
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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
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Deriving Causal Inferences
• Arriving at causation from association For example, showing that Helicobacter
pylori is directly linked to peptic ulcers
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Perspectives
• Causation may be limited
• Subject to modification
• Perhaps more complex than realized
• Sometimes not measureable
• “Criteria” are really guidelinesmay be subjective