Causal Association

Question 1

define cause

Answer 1

any exposure leads to new cases of disease

we can only prevent diseases by removing exposure(s) to causal factors

Question 2

can we every prove causation?

Answer 2

no

Question 3

how to we establish a causal relationship?

Answer 3

1. elaborating on the nature of the causal association
   -developing a causal web or diagram
2. assessing the likelihood that a causal association exists
   -applying guidelines like Hill’s criteria
3. demonstrating that a valid association exists
   -eivdence

Question 4

how do we elaborate causal associations or mechanisms?

Answer 4

1. epi triad
2. causal path models/causal web
   -interrelationship of multiple factors that contribute to the occurrence of disease
3. component cause model/causal pie/necessary sufficient cause model
4. statistical models

Question 5

describe the causal pie or component cause model of causation

Answer 5

1. cause: an event/state of nature which initiates (alone or in conjunction with other causes) a sequence of events resulting in an effect
2. sufficient cause: a causal complement which inevitably results in the effect
3. component cause: part of a causal complement (one piece of the pie)
4. necessary cause: a component cause which is a member of every sufficient cause

Question 6

describe henle-koch’s postulates

Answer 6

1. organism is found in all cases of disease
2. organism is not found in other individuals as a non-pathogenic parasite
3. it must be possible to produce a pure, sustainable culture of the organism
4. it must be possible to experimentally reproduce the same disease in a susceptible host

Question 7

describe bradford-hill’s causal criteria

Answer 7

1. temporal sequence: exposure must precede disease
   -cohort studies help
2. strength of association: exposure more common in disease
   -strong associations are less likely to be due to chance or bias
3. consistency of effect (replication)
   -strength of association may differ but direction should be the same
   -relationships demonstrated in multiple studies are more likely to be causal
4. biological gradient: changes in exposure related to changes in disease risk
   -an association is more likely to be causal if frequency of disease varies directly with the amount of exposure
5. specificity of association: one exposure, one disease
   -easier to demonstrate support for causation when associations are specific
6. coherence with established facts: proposed causal mechanism should be plausible
7. biologic plausibility:
   -an association is more likely to be causal if it is biologically sensible
8. analogy: similar evidence between another exposure-disease relationship
   -similar evidence can provide support for a causal association
9. experiment
   -experimental evidence: did intervention prevent disease
   -experimentation may provide support for the causal hypothesis

not a checklist! don’t need all of them, jsut helps build your case

Question 8

is strength of association equivalent to statistical significance

Answer 8

NO