Measuring Disease in Populations

Question 0

Define prevalence.

Answer 0

Proportion of people that have a disease.

Question 1

Define incidence rate.

Answer 1

Number of new cases per population per year.

Question 2

How is prevalence increased?

Answer 2

Increased incidence, keeping patients alive longer.

Question 3

How is prevalence decreased?

Answer 3

Reduced incidence (prevention), curing patients, more patients dying.

Question 4

How is systematic variation of risk between different groups useful?

Answer 4

Gives association between levels of exposure and the disease which can help identify the aetiology (cause). Once identified, it may be possible to reduce the expose and therefore the incidence.

Question 5

How can systematic variation be a nuisance?

Answer 5

Confounding factors such as age and sex cannot be changed but can influence the crude incidence/mortality ratio between groups so observed risk differs from the true risk of that exposure (eg. Bournemouth and melanoma, confounded is age)

Question 6

Define confounding factor.

Answer 6

A factor associated with both the exposure of interest and the outcome being measured but not on the causal pathway between exposure and outcome.

Question 7

What is the point of age-sex standardisation? (eg. SMR)

Answer 7

It deals with the confounding factors to give results closer to the true risk and a better idea whether there is a causal link.