Incidence (epidemiology)

( " Happen " Latin incidere ) The incidence is an epidemiological measure and thus technical term from the medical statistics. It is the number of new cases under certain criteria:

• A particular disease
• A population of defined size (usually 100,000)
• During a certain time (typically one year )

Since it is in the incidence to a relative size, one has to strictly speak of the incidence rate:

Often it is unified as "Number of new cases per year per 100,000 population " is specified. The incidence is to be distinguished by the prevalence.

Consideration of different effects

Under crude incidence is the ratio of one year newly diagnosed persons to the total population of a given region. This measure can be well used to, for example, offer sufficient treatment courts can or to determine an increase / decrease in new infections in a given disease.

However, there are diseases that occur with varying frequency depending on age, gender or region. One can, for example, a region with many old people compare hard with a region with many young people. If, however, the crude incidence flips to a standard population can be compared to good, whether a disease is more common in a region compared to another. This measure is spoken by an age- standardized incidence.

Using the same principle also works the calculation of:

• Age-specific incidence after 5 - and 10 - year age groups
• Cumulative incidence

Example

In a group of 2000 male smoking at the age of 60 to 80 years, heart attacks occurred during an observation period of one year in 76 patients for the first time. Thus, the age-specific incidence rate is = 76/2000 = 0.038 p. or a 3.8% per year.