3. Measuring Disease in Populations Flashcards
How can the incidence rate be calculated? (Give the units of incidence rate).
Incidence rate = new events/ (person x time (years)) = events per persons per year.
What does prevalence measure?
The number of existing cases at a certain fixed point in time. It is a proportion not a rate.
What formula sums up the relationship between incidence and prevalence?
P = I x L Prevalence = incidence x length of disease
How can systematic variations be used alongside incidence ratio?
Look at people within the same risk category, e.g. high risk patients together. It can be used to identify a possible aetiology (cause) of a disease.
Why is identifying the aetiology of a disease helpful?
It may be possible to put actions in place to prevent exposure to that causes and therefore decrease incidence of the disease.
How can the incidence rate ratio be calculated?
IRR = RateB / RateA
Incidence rate ratio = incidence rate of exposed / incidence rate of unexposed.
How can IRR calculations be used to work out the most effective treatment?
Calculate it using data regarding the efficacy (e.g. use mortality rates) of two different treatments in the calculation, i.e. IRR = mortality rate B (new drug) / mortality rate A (existing drug).
What is a measure of absolute risk?
Rate.
What is a measure of relative risk?
Ratio.
What is a confounding factor?
A factor that can explain all or part of an apparent association between an exposure and a disease but is not the cause of the link.
How can the effects of the confounding factor age, be avoided? What is a possible problem with this solution?
By using age-specific rate ratios. Too many answers are produced, which can be hard to interpret.
What is the SMR?
A comparison of expected number of deaths with the observed number of deaths if a standard reference populations age-sex specific rates were applied to the study population’s age-sex groups.
What does the incidence rate measure?
New cases of a disease.
