Incidence Rate

What is Incidence Rate?

The incidence rate is a term used to refer to the occurrence of new cases involving disease or injury in the population over a period. Epidemiologists use this term to mean a number of new cases in a community while others use the term to refer to the number of new cases per unit of population.

Incidence rate allows us to anticipate future incidents and plan accordingly. It is usually expressed as a number of cases per person-year of observation. Under calculation, only new cases are observed and not old ones. The data for ‘population at risk’ is usually obtained from census data.

This provides information on the number of new cases of a disease or other incident within a community and helps in tracking changes in the progression of disease under observation among the population over a period of time. Therefore, it serves as an important metric for tracking infectious disease like tuberculosis and malaria.

Incidence rate can also be categorised by different characteristics like race, gender and age.

Incidence VS Prevalence

Incidence and Prevalence are different and should not be confused with each other. Prevalence measures the number of cases of an illness in a population at a certain point in time whereas incidence measures something during a specific period of time. Prevalence is the total accumulation of incidences over a time period.

For instance, the incidence of loan foreclosures would be the number of foreclosed loans over a time period. Prevalence would be the total number of all incidences. The same way, incidence of malaria disease would be the number of people infected. Prevalence would be the total number of people. Incidence helps in the assessment of risk contracting a disease whereas prevalence shows whether this disease is widespread or not.