Incidence Rates in Persons Years

Question 1

Incidence Rate Formula

Answer 1

Event / (Person * Time)

Question 2

Calculating Person Years

Answer 2

Take time and multiply it by number of people

Question 3

Drawback of Incidence Rate

Answer 3

Person time assumes event is constant for the entire study period

Question 4

Converting Person Years

Answer 4

Event / 1000 persons years
- Can represent in other time horizons

1. 500 people for 2 years
2. 1000 people for 1 year
3. 100 people for 10 years

Question 5

Simple Proportional vs Incidence Rate

Answer 5

Conceptually both methods are the same
- Proportion: need to treat 53 people for 3.8 years to prevent one event
- Incidence Rate: need to treat 200 patients for 1 year to prevent one event

Incidence Rate is just better formatted