Measuring Disease In Populations

Question 0

Explain Incidence Rate Ratio (IRR)

Answer 0

RateA/RateB

If rate > 1.0 - group A at greater risk than group B (incidence is x times)

Question 1

Define and differentiate between the terms ‘incidence’ and ‘prevalence’ and describe the inter-relationships between incidence and prevalence and changing patterns of death of cure

Answer 1

Incidence rate - number of new cases of the disease per 1000 people per year
Prevalence - amount of people who currently have the disease in a set population
Incidence affects prevalence, prevalence affected by death or cure

Question 2

Explain the purpose of age/sex standardisation

Answer 2

Avoids confounding of age and sex

Question 3

Interpret a Standardised Mortality/Morbidity Ratio (SMR)

Answer 3

Expressed as a percentage
SMR = 100 - same mortality
SMR > 100 - excess mortality
SMR < 100 - lower than average mortality

Question 4

What is a ‘confounding factor’?

Answer 4

A confounder is something that is associated with both the outcome and the exposure of interest, but is not on the causal pathway between exposure and outcome
Confounding factors distort and give misleading results

Question 5

Explain Incidence Rate

Answer 5

IR = new events/(person x time (years))