Association and Causation

Question 1

What is the primary goal of epidemiological studies?

Answer 1

To identify causes of diseases or health issues to guide prevention, diagnosis, and treatment.

Question 2

What is the difference between association and causation?

Answer 2

Association means two variables occur together more often than by chance, while causation means one variable directly affects the other.

Question 3

Define a ‘necessary cause’ in the context of causation.

Answer 3

A necessary cause is a factor that must be present for a disease to occur, but it may not be sufficient on its own to cause the disease.

Question 4

Define a ‘sufficient cause’ in the context of causation.

Answer 4

A sufficient cause is a factor that alone can produce or initiate an outcome.

Question 5

What is a spurious association, and why does it occur?

Answer 5

A spurious association is a false connection due to chance or bias, often caused by flaws in study design.

Question 6

What is a statistical association?

Answer 6

A relationship where two variables are linked due to a shared underlying factor, not causation.

Question 7

Provide an example of a non-causal statistical association.

Answer 7

High altitude and goiter: they appear associated, but the true cause is iodine deficiency common in high-altitude areas.

Question 8

What type of association results from selection bias?

Answer 8

Spurious or false association due to differences in groups that are not accounted for in the study design.

Question 9

What is a one-to-one causal relationship? Provide an example.

Answer 9

A model where the presence of a specific factor always leads to a particular disease. Example: Measles virus causing measles.

Question 10

What is multifactorial causation, and why is it important in epidemiology?

Answer 10

A model where multiple factors contribute to disease development, often seen in chronic diseases like cardiovascular disease.

Question 11

In the multifactorial model, what is the difference between independent and cumulative causation?

Answer 11

Independent causation: factors act alone to cause disease; cumulative causation: multiple factors interact to produce disease.

Question 12

What is the purpose of the Bradford Hill Criteria?

Answer 12

To determine whether an association between two variables is likely to be causal.

Question 13

What does ‘temporal association’ mean in the Bradford Hill Criteria?

Answer 13

The suspected cause must occur before the observed effect for the association to be considered causal.

Question 14

How does ‘strength of association’ support causality?

Answer 14

A stronger association (higher relative risk) increases the likelihood that the relationship is causal.

Question 15

Why is ‘specificity of association’ challenging to establish in epidemiology?

Answer 15

Because many diseases have multiple causes, and a single cause can lead to multiple diseases, making one-to-one relationships rare.

Question 16

What does ‘biological plausibility’ mean in the context of causation?

Answer 16

The association aligns with known biological mechanisms, making the causal relationship more credible.

Question 17

Give an example of ‘consistency of association’ in epidemiological studies.

Answer 17

The link between smoking and lung cancer, consistently observed across many studies worldwide.

Question 18

What role does ‘coherence’ play in judging causality?

Answer 18

Coherence ensures that the association does not contradict established knowledge and historical data trends.

Question 19

What is the ‘web of causation,’ and why is it significant in multifactorial diseases like ischemic heart disease (IHD)?

Answer 19

The web of causation illustrates how multiple factors interact in complex ways to cause diseases, which is crucial in multifactorial diseases.

Question 20

What is a ‘confounding variable,’ and how does it affect association interpretation?

Answer 20

A confounding variable is an external factor linked to both the exposure and outcome that can create a misleading association if not accounted for.

Question 21

Explain how selection bias might lead to a false association using the example of hospital vs. home births.

Answer 21

Higher-risk pregnancies are more likely to occur in hospitals, creating a misleading association that hospital births are riskier.

Question 22

How is the correlation coefficient used in determining associations, and what are its limitations?

Answer 22

The correlation coefficient (ranging from -1 to +1) measures the strength of association but does not prove causation since it lacks a temporal sequence.

Question 23

Why can cigarette smoking and sugar intake show a spurious association in relation to coronary heart disease (CHD)?

Answer 23

Smoking is linked with increased hot drink and sugar intake; however, only smoking, not sugar, is causally related to CHD.

Question 24

What does it mean for a cause to be ‘necessary but not sufficient’ in the case of tuberculosis?

Answer 24

The tubercle bacilli are necessary for tuberculosis but are not sufficient alone, as additional factors like poor living conditions increase disease risk.

Question 25

What example from the Bradford Hill Criteria illustrates ‘dose-response relationship’ with smoking and lung cancer?

Answer 25

Increased lung cancer risk correlates with the number of cigarettes smoked daily, showing a dose-response relationship.

Question 26

Describe ‘coherence’ in the context of lung cancer and smoking trends in men and women.

Answer 26

Historical coherence is seen as smoking rose first in men, followed by women, with lung cancer trends reflecting this shift.

Question 27

Why is ‘specificity of association’ often considered the least applicable Bradford Hill criterion?

Answer 27

Specificity is challenging because most diseases result from multiple causes, and single exposures can lead to various outcomes.

Question 28

According to the Bradford Hill Criteria, why is ‘biological plausibility’ important, and give an example related to skin cancer.

Answer 28

Biological plausibility requires that the association makes sense biologically, such as UV exposure leading to skin cancer, which fits known biological mechanisms.