Case-control studies

Question 1

What is a case-control study

Answer 1

A case control study looks at individuals with a disease, often a rare disease, and compares it with individuals without. It then investigates whether a particular risk factor increases the risk of the outcome of the disease. It compares the frequency of the exposure between those with the disease and those without, and tries to determine the association.

Question 2

What is the difference between a case control study and a retrospective cohort study

Answer 2

A retrospective cohort study selects people based on exposure, whereas a case-control study selects people based on an outcome.

A case control study assesses the prevalence of an exposure in a group with a particular outcome status, whereas a retrospective cohort study looks at the INCIDENCE OF AN OUTCOME based on a exposure.

Question 3

Advantages of case control studies

Answer 3

Cheaper and less time consuming
Good for studying rare diseases
Smaller sample sizes required

Question 4

Disavantages of case control studies

Answer 4

Selection bias - how do we select the ‘case’ and the control
Cannot demonstrate causality
Recall bias
Difficult to establish causal relationship