Cohort Studies

Question 1

Within Cohort Comparison.

Answer 1

Recruit outcome free individuals.
Classify into exposed and un exposed.

IRexposed = those who developed the disease/p-yrs of exposure
IRunexposed = those who developed the disease/p-yrs of exposure

IRR = IRexposed/IRunexposed

Question 2

Concurrent/Prospective Cohort Study

Answer 2

follow up in future
outcome free individuals at the start
takes years, resource intensive, can control exposure, can collect specific data.

Question 3

Historical/Retrospective Cohort Study

Answer 3

start collecting follow up data from the past.

quicker, less resource intensive, can’t control exposure, historical records may not be as accurate or specific.

Question 4

Person-years

Answer 4

The sum of the total time of everybody followed up in the study

Question 5

External Comparison

Answer 5

use SMR

Lexis Diagram - takes into account that the study population ages during the course of the study