1. Brief Intro to Case-Control Studies
4/27/2017
Cohort Studies
Recruit cohort  sub-divide cohort into exposed and non-exposed sub-cohorts
 follow individual over time
cohort-vs-case-control-brief.ppt
Cohort & Case-Control Basics
cohort-vs-case-control-brief.ppt

2. Cohort Study: CytoMegaloVirus and Restenosis
Total
CMV +
CMV − 21 28 49 2 24 26 75
Risk in the exposed group
Risk in the non-exposed group
cohort-vs-case-control-brief.ppt
Cohort & Case-Control Basics

3. Cohort Study: CytoMegaloVirus and Restenosis
Total
CMV +
CMV − 21 28 49 2 24 26
= CMV+ group had 5.57 times the risk as CMV- group
Can be converted to a “relative risk difference” (RRD) for discussion
cohort-vs-case-control-brief.ppt
Cohort & Case-Control Basics

4. Cohort Study: CytoMegaloVirus and Restenosis
Total
CMV +
CMV − 21 28 49 2 24 26
“Excess risk” on an absolute scale
cohort-vs-case-control-brief.ppt
Cohort & Case-Control Basics

5. Cohort Study: CytoMegaloVirus and Restenosis
Total
CMV +
CMV − 21 28 49 2 24 26
Attributable fraction in exposed cases
Prop of cases that are exposed
Attributable fraction in population
cohort-vs-case-control-brief.ppt
Cohort & Case-Control Basics

6. Brief Intro to Case-Control Studies
4/27/2017
Case-Control Studies
Identify all cases and [small number] non-cases
 ascertain exposure history of cases and non-cases
cohort-vs-case-control-brief.ppt
Cohort & Case-Control Basics
cohort-vs-case-control-brief.ppt

7. Case-Control: Grilled meat and Pancreatic Cancer
PCa+
PCa−
Meat +
Meat − 53 53 ?? 85 43 ?? 96 96
168
Interpret just like an RR
cohort-vs-case-control-brief.ppt
Cohort & Case-Control Basics