Study Design Lecture

1. Week 2
Study design
EPID 504D
Emory Rollins School of Public Health

2. Overview
• Cohort and case-control studies
– Relationship between exposure and disease
– Prospective or retrospective
– Advantages and disadvantages

3. Cohort study
• Cohort is a well-defined population
– Students in a classroom or school
– Conference attendees
– Cruise ship passengers
– Company employees
– City residents

4. Cohort study
• Exposures
associated
with disease?

5. Cohort study
• Prospective
– Framingham example
• Retrospective
– Breast cancer example

6. Cohort study issues
• Potential biases
• Expensive
• Time intensive
• Rare disease=large numbers

7. Case-control study
• Disease
associated with
the exposure?

8. Control selection
• Control selection
– Hospitalized controls
– Community controls
– Multiple types
• How many?
– 1-4 controls per case

9. Nested case-control study
• “Efficient” cohort study
• Select controls among
non-diseased

10. Cross-sectional study
• Assess disease and
exposure at the same
time
• Difficult to assess
causality

11. Readings
• Chapter 9: p. 167–175
• Chapter 10: p. 177–185; 187–193; 195–8