Measures of Disease Frequency Flashcards
Prevalence of a disease
proportion of the population who have the disease at the relevant time
Period prevalence
proportion of the population affected over a given period
Incidence of a disease
number of new cases of disease occurring in a given population over a given period of time
How to calculate incidence
no. new cases during time period / total pop. at risk
Risk
probability that an event will occur
risk = diseased (exposed) / diseased + healthy (exposed)
A/(A+B)
Rate
number of events occurring in a population over a period of time
Odds
A/B
Absolute risk
the risk numerically in a group
Relative risk
term used to refer to a number of different measures of effect
Risk ratio of disease in exposed to non-exposed
(A/(A+B)) / (C/(C+D))
Attributable risk
difference in risk of a condition between exposed and unexposed population
Number needed to treat
average number of patients who need to be treated to prevent one additional bad outcome
NNT calculation
1/reduction in absolute risk
