Measuring Disease In Populations Flashcards
Define prevalence.
Prevalence is a measure of existing cases. It gives a proportion of the population which have the disease at a particular moment in time.
Give two factors which increase and two factors which decrease prevalence.
Increase: life expectancy, incidence
Decrease: cure, death
What is an incidence rate ratio?
It is a calculation which allows to compare incident rates between two groups of people (normally with different exposures). This allows us to identify causal factors and then limit these and reduce prevalence of disease.
What type of risk is the IRR a measure of?
Relative risk. It simply compares the risks between the two groups. Incidence rate is a measure of absolute risk.
Why are systematic variations useful?
We can look at them and compare then to find out about the aetiology of disease or to compare different treatments.
Some can be nuisance and not useful however.
What is a confounding factor?
This is something which is linked to both the exposure and the outcome. For example it could be said that alcohol leads to lung cancer, but in fact it caused by the confounding because a person who drinks is more likely to smoke and smoking causes lung cancer.
What is an indirect SMR?
This is where rather than comparing two populations, the observed mortality in a study population is compared to the expected mortality in a standard population.
What is incident rate and how do we calculate it?
Incident rate is the populations average risk of disease.
It is calculated by dividing the number of cases by the number of people and the time (years). This gives a number which has the unit cases per person years.
