Causality - L12

Question 1

What is the purpose of population health?

Answer 1

Provide the maximum benefit for the largest number of people, at the same time reducing inequities in the distribution of health and well-being

Question 2

What study could be used to define the problem?

Answer 2

Cross-sectional studies
e.g. survey asking BMI to determine obesity levels in the population

Question 3

What study is suitable to identify risk and protective factors?

Answer 3

Cohort (observational studies)
e.g. what effect does high fat diet have on BMI over time?

Question 4

What study is suitable in order to develop and test prevention strategies?

Answer 4

Randomised controlled trial
Diagnostic tests

Question 5

Does epidemiology determine the cause of a disease in an individual?

Answer 5

No - determines the relationship between an exposure and outcome in populations

Question 6

Can preventative measures function before the cause or determinant of a dis-ease is identified?

Answer 6

Yes - e.g James Lind’s experiment

Question 7

What is James Lind’s experiment?

Answer 7

An early form of a controlled trial in which sailors were given a set diet including citric acid fruit in order to test for the cause of Scurvy
The idea that citric acid fruit should be included in the diet was found before people knew Scurvy was caused by a vitamin C deficiency

Question 8

What is the Bradford Hill framework?

Answer 8

A guide that aids in determining whether a relationship between an exposure and outcome is causal or not

Question 9

What are the components of the Bradford Hill Framework?

Answer 9

Temporality
Strength of association
Consistency of association
Biological gradient
Biological plausibility of association
Specificity of association
Reversibility

Question 10

What is temporality in the Bradford Hill framework?

Answer 10

The exposure must come before the outcome

Question 11

What is strength of association in the Bradford Hill framework?

Answer 11

By comparing relative risk values between exposure and comparison groups -> a greater relative risk value shows stronger association hence a causal relationship is more likely

Question 12

What is consistency of association in the Bradford Hill framework?

Answer 12

Replication of the results by different investigators, at different times, by different methods in different places should show similar results

Question 13

What is biological gradient (dose-response) in the Bradford Hill framework?

Answer 13

Increase in the magnitude of the exposure should be reflected in the the increase of the magnitude of the outcome

Question 14

What is biological plausibility of association in the Bradford Hill framework?

Answer 14

Association should make biological sense - > explained by science

Question 15

What is specificity of association in the Bradford Hill framework?

Answer 15

The idea that a single cause should lead to a single outcome -> not relevant as dis-ease occurrences are often due to multiple exposures

Question 16

What is reversibility in the Bradford Hill Framework?

Answer 16

Changing the exposure in a study should change the outcome

Question 17

What is a cause of a disease?

Answer 17

An event, condition, characteristic or combination of these factors which play an essential role in producing the disease

Question 18

What is the causal pie?

Answer 18

A visual representation of the existence of multiple causes to a disease

Question 19

What are the three types of causes?

Answer 19

Sufficient cause
Component cause
Necessary cause

Question 20

What is sufficient cause?

Answer 20

The whole pie - the minimum set of conditions without any one of which the disease would not occur
Represents that multiple causes contribute to the occurrence of a disease
Probability of disease = 1

Question 21

What is a component cause?

Answer 21

Each factor or slice of the causal pie - a factor that contributes towards the disease but is not sufficient to cause dis-ease on its own
Probability of disease when present = 0 - 1

Question 22

What is a necessary cause?

Answer 22

A slice of the causal pie - a factor which when not present will not lead to the causation of the disease
Probability of disease when present is not 0

Question 23

What is the general definition of causation

Answer 23

The presence or absence of the cause makes a difference in the outcome