Incidensandel

Incidensandel is a statistical concept used in epidemiology to express the share of new disease cases in a population that is attributed to a defined subgroup during a specified time period. It represents the proportion of incident cases that occur within the subgroup relative to the total number of incident cases in the population.

Calculation and interpretation: incidensandel of a subgroup = (number of incident cases in the subgroup during the period) / (total incident cases in the population during the period). It is typically reported as a percentage. This measure differs from incidence rate, which uses person-time, and from the incidence proportion (risk) for the entire population rather than for a subgroup.

Applications: incidensandel is used to understand how the overall burden of a disease is distributed across subgroups, such as age, sex, geographic region, or presence of a risk factor. It helps in comparing disparities, planning interventions, and allocating health resources by highlighting which groups contribute more to new cases in a given period.

Data considerations and limitations: calculating incidensandel requires accurate counts of new cases and a well-defined at-risk population for the period. Biases from underreporting, misclassification, or differing testing practices can distort the share. The choice of time window and subgroup definitions affects comparability and stability, especially for rare diseases or small populations.

Relation to related metrics: incidensandel is complementary to measures of incidence, burden, and risk. It does not itself quantify risk but describes how incidence is distributed across subgroups, aiding interpretation of public health impact and priorities.