Chapter 9: Comparing Cohort and Case-Control Studies

Question 1

What is the primary difference between the design of a cohort and case-control study?

Answer 1

In a cohort study, exposed and unexposed persons are compared and in a case-control study the persons with the disease (cases) and without the disease (control) are compared

Question 2

What rates of disease can we study with a cohort?

Answer 2

• Absolute risk (incidence)
• Relative risk (risk ratio or rate ratio)
• Risk difference
• Attributable proportion (attributable risk %)

Question 3

How to calculate the incidence among exposed

Answer 3

a/(a+b)

Question 4

How to calculate the incidence among unexposed

Answer 4

c/(c+d)

Question 5

Can you determine a temporal relationship in cohort studies?

Answer 5

Yes

Question 6

What is an advantage of a prospective cohort?

Answer 6

• can study multiple EXPOSURES, such as HTN, smoking, obesity, cholesterol levels in Framingham study
• can study multiple outcomes of a single exposure
• better exposure and confounder data
• less vulnerable to bias
• temporality established

Question 7

Disadvantages of prospective cohort

Answer 7

• more expensive and time consuming
• it may take a long long time for the exposure to happen
• funding for study may run out
• investigator may die
• hypothesis may be shown to be invalid from other studies
• not good for rare outcomes
• selection bias (biggest), information bias, misclassification bias

Question 8

What are some advantages of a retrospective cohort study?

Answer 8

1. quicker and cheaper
2. more efficient for diseases with long latent periods

Question 9

What is the primary disadvantage of retrospective cohort studies?

Answer 9

Missing information