Lecture 16: Measuring disease occurrence

Question 1

What is prevalence and why is it important? (include the equation)

Answer 1

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

Why:
- to understand Burden of disease
- to understand Resource allocation

(Number of people with the disease at a given point in time) / (Total number of people in the population at that point in time)

Question 2

What are some limitations of prevalence?

Answer 2

Prevalence - limitations
1. Difficult to assess the development of disease
2. Is influenced by the duration of the disease

Question 3

What is incidence?

Answer 3

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

Question 4

What is incidence proportion, equation and limits?

Answer 4

The proportion of an outcome-free population that develops the outcome of interest in a specified time period

(Number of people who develop the disease in a specified period) / (Number of people at risk of developing the disease at the start of the period)

limitations:
* Assumes a ‘closed’ population (does not account for people coming or going)
* Highly dependent on the time period (longer time period = higher incidence proportion)

Question 5

What is incidence rate, equation and limits?

Answer 5

The rate at which new cases of the outcome of interest occur in a population

(Number of people who develop the disease in a specified period) / (Number of person-years at risk of developing the disease)

Limitations:
- if Person-time not available can’t do it
- complex to calculate

Question 6

When would we use age standardisation? (do not need to calculate)

Answer 6

When Age structures differ AND Disease risk varies by age