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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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Sequence of studies l.jpg

Clinical observations

Available data

Case-control studies

Cohort studies

Randomized trials

Sequence of Studies


Types of associations l.jpg
Types of Associations

  • Real

  • Spurious


Definitions l.jpg
DEFINITIONS

  • Observational study

  • Causation

  • Etiology

  • Association

  • Necessary

  • Sufficient

Your Assignment:

Define these terms

as they apply to

epidemiology.


Koch and causation l.jpg
Koch and Causation

  • Postulates

  • Why study association?

  • Web of causation

  • Do we need a better way?


Twelve criteria for causation l.jpg

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 l.jpg
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 l.jpg
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 l.jpg
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 association Direct association

    • No possibility for association

    • Possibly associated

    • Associated

    • Direct 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 guidelines

    • may be subjective


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