Differences between Case Control and Cohort Studies

Case Control Study

Cohort Study

•       Proceeds from effect to cause

1. Proceeds from cause to effect

•       Starts with disease

2. Starts with healthy people

•       Tests whether the suspected cause occurs more frequently in those with disease than those among without disease.

3. Tests whether disease occurs more frequently in those exposed or in those not exposed.

•       Usually the first approach for testing the hypothesis.

4. Reserved for testing of precisely formulated hypothesis.

•       Involves fewer no of subjects

5. Involves larger no of subjects

•       Yields relatively quick results

6. Yields delayed results

•       Suitable for study of rare diseases

7. Inappropriate for rare diseases

•       Generally yields only estimate of OR

8. Yields Incidence, RR & AR

•       Cannot yield info about diseases other than that selected for study

9. Can yield information about more than one disease.

•       Relatively inexpensive

10. Expensive