Types Of Studies

Question 1

Describe a cohort study

Answer 1

Recruit outcome free individuals
Classify into exposed and unexposed groups 
Follow up each group over time:
- count the person years (p-y)
- count how many develop outcome (d)
- calculation incidence rate (IR=d/p-y)
Analyse each exposure group separately 
Compare exposure groups by calculating incidence Rate Ratio (IRR) 
- IRR= IR (exposed)/IR (unexposed)

Question 2

What are the two different types of a cohort study?

Answer 2

Prospective

Retrospective

Question 3

How do you calculate Incidence rate?

Answer 3

IR=d/p-y

Question 4

What is a person year?

Answer 4

The sum of the total time of everybody in a study

Question 5

What is a case control study?

Answer 5

In the present you identify groups that have the case and those that don’t (control group)
Go back in time to see if they were exposed or not the relevant differentials
Always retrospective

Question 6

What is a disadvantage to observation studies?

Answer 6

Can’t show causation, only association

Question 7

What is an advantage to cohort studies?

Answer 7

You can be sure exposure occurred before outcome

Can show multiple outcomes

Question 8

What is a disadvantage to cohort studies?

Answer 8

Lots of follow up issues

Question 9

What is an advantage to case-control study?

Answer 9

Quicker than cohort
Good for rare diseases
Can match thus minimising confounding