This document discusses the relationship between association and causation in epidemiology. It defines key terms like observational study, causation, etiology, association, necessary and sufficient. It also outlines Koch's postulates and 12 criteria for determining causation. Factors that can influence disease causation are discussed, as are degrees of association and guidelines for judging whether an association is causal. The document notes that determining causation from association requires careful consideration and causation may be more complex than criteria suggest.

1. Association to Causation
BY
DR MUHAMMAD TAUSEEF JAVED
CONSULTANT MINISTRY OF
HEALTH MAKKAH
&
IPH LAHORE

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

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. 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

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