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Latest revision as of 12:50, 18 March 2025
Incidence refers to the occurrence, rate, or frequency of a disease, crime, or something else undesirable. In epidemiology, it is a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate.
Definition[edit]
The incidence of a medical condition is the frequency at which it occurs in a population over a certain time period. It is commonly reported in the number of cases per 1,000 or 100,000 people per year. The incidence rate is the number of new cases per population at risk in a given time period<ref>Porta, Miquel, ed. (2014). "Incidence rate". A Dictionary of Epidemiology (6th ed.). Oxford University Press. p. 112. ISBN 978-0-19-997673-7.</ref>.
Calculation[edit]
When the denominator is the sum of the person-time of the at risk population, it is also known as the incidence density rate or person-time incidence rate. Using person-time rather than just time handles situations where the amount of observation time differs between people, or when the population at risk varies with time<ref>Porta, Miquel, ed. (2014). "Incidence rate". A Dictionary of Epidemiology (6th ed.). Oxford University Press. p. 112. ISBN 978-0-19-997673-7.</ref>.
Incidence versus Prevalence[edit]
Incidence should not be confused with prevalence, which is a measure of the total number of cases of disease in a population at a given time rather than the rate of occurrence of new cases. Thus, incidence conveys information about the risk of contracting the disease, whereas prevalence indicates how widespread the disease is<ref>Porta, Miquel, ed. (2014). "Incidence rate". A Dictionary of Epidemiology (6th ed.). Oxford University Press. p. 112. ISBN 978-0-19-997673-7.</ref>.
See Also[edit]
References[edit]
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