1. Jeanne M. Clark, MD, MPH Division of General Internal Medicine
Cohort Study Overview
Jeanne M. Clark, MD, MPH
Division of General Internal Medicine

2. Design of Cohort Studies
Examples:
JHU Precursors Study
Framingham Study
Identify:
Exposed
Develops Disease
No Disease
Not Exposed
Defined Population
Non-random selection
Can start here: (less common)

3. Prospective (Concurrent) Cohort
2000
2001
2008
Exposed
Develops Disease
No Disease
Not Exposed
Defined Population
Non-random selection
Typically active, scheduled follow-up of some kind

4. Retrospective (Non-Concurrent) Cohort
1988
1998
2008
Exposed
Develops Disease
No Disease
Not Exposed
Defined Population
Non-random selection
Generally passive or post-hoc follow-up of some kind

5. Analysis of Cohort Studies
Then follow to see:
Start with:
Develops Disease
No Disease
Totals
Incidence Rates
Exposed a b
a+b
a/a+b
Not Exposed c d
c+d
c/c+d

6. Comparison of 4 Major Study Designs
Goal or Feature RCT CS CC X-S
Estimate Prevalence F F F A+
Estimate Incidence B- A+ F F
Prove Causality A+ B+ B- D
Generalizability B- A- A- A
Feasibility C B A A
RCT=Randomized, controlled trial; CS=Cohort study;
CC=Case-control study; X-S=Cross-sectional study