Lecture 5: Measure disease occurrence

Question 1

What is prevalence?

What are the limitations?

Answer 1

The proportion of a population who have a disease as at a given point in time

• prevalence does not accept for length of disease - only shows one point in time

Question 2

What is incidence?

Answer 2

The occurrence of new cases of an outcome in a population during a specific period

Question 3

What is cumulative incidence (CI)?

What are the limitations?

Answer 3

Is the proportion of people who develop a disease during a specific time period

• assumes a closed population. Is dependant on time period

Question 4

What is the incidence rate?

What are the limitations?

Answer 4

Is the rate at which new cases of the outcome of interest occur in a population
——-> shows the speed of new cases during a time period

• not dependant on disease duration

Question 5

When do we age standardise?

Answer 5

You age standardise when age structure of populations are different - populations differ my age
- When the condition you look at varies by age

Question 6

How do you calculate prevalence?

Answer 6

= # cases at a given point in time

/ # in the population at that time

Question 7

How do we calculate cumulative incidence?

Answer 7

= # cases during a given time period

/ 3 at risk of developing disease AT THE START of the period

Question 8

How do we calculate incidence rate?

Answer 8

= # cases during a given time period

/ person-time at risk during period

Question 9

What is age standardisation?

Why do we age standardise?

Answer 9

Age is a cause for different disease rates in different groups, so you ages standardise “ making the have the same age distributions”
- Age increases/decreases risks for certain condiments and if different groups have different age distributions then this could confound their data making them look at higher risk for disease when the difference is actually due to their ages