Lecture 29 - Association and causation

Question 1

What is association

Answer 1

A relationship between two variables where changes in one are reflected in changes in the other

Question 2

What is a cause

Answer 2

an event, condition or characteristic that plays an essential role in producing an occurrence of disease

Question 3

Does an association mean causation

Answer 3

No, association alone doesn’t imply causation. We must evaluate whether the association is causal using valid criteria

Question 4

Causal pie model

Answer 4

• Sufficient cause: A combination of factors that result in the outcome
• Component cause: Each factor contributing to the outcome

Each exposure is a component of the sufficient cause

Question 5

Eliminating exposure

Answer 5

eliminating a component cause from a sufficient cause can help prevent the disease.
A component cause which is necessary for the disease to occur. It must be part of every sufficient cause

Question 6

Necessary cause

Answer 6

A cause that must be present for the disease to occur

Question 7

How to determine causation

Answer 7

1. Is there an association?
2. Is the association valid?
3. Does the association imply causation?

Question 8

How do we determine if something is causal?

Answer 8

Using the Bradford hill criteria for causality. The guidelines

Question 9

Guidelines

Answer 9

Consider each of the guidelines and then make a judgement based on the totality of evidence

Question 10

What are the guidelines

Answer 10

1. Biological plausibility
2. Experimental evidence
3. Specificity
4. Temporal sequencing
5. Consistency
6. Dose-Response relationship
7. Strength of association
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Question 11

Biological plausibility

Answer 11

Is there a plausible mechanism for the association. it refers to whether there is a logical, scientifically reasonable explanation for an observed association.

Question 12

Experimental evidence

Answer 12

Is there evidence from human RCTs or animal experiments? evidence that supports or refute an observed association between exposure and outcome

Question 13

Specificity

Answer 13

Is the exposure specifically associated with a particular outcome but not others? When an exposure consistently leads to a particular outcome and not others, it strengthens the argument for a causal relationship between the two.

Question 14

Temporal sequencing

Answer 14

Referes to the requirement that the exposure must occur before the outcome for a causal relationship to be possible.

Question 15

Consistency

Answer 15

Are the findings consistent with findings from other studies? If an association between an exposure and an outcome is repeatedly observed in multiple studies, it strengthens the case that the association might be causal.

Question 16

Dose-response relationship

Answer 16

Does the risk of the outcome change with increasing or decreasing amounts of the exposure?
in a dose-response relationship, as the exposure increase or decreases, the likelihood or severity of the outcome also changes in a predictable way.

Question 17

Strength of association

Answer 17

The stronger the association, the less likely it is to be due to confounding or bias.