What is an incidence rate and what does it mean for your research? July 11, 2015 Incidence rate in epidemiology can be confusing to say the least. In healthcare and the study of disease, an incidence rate refers to the rate of newly diagnosed cases of a disease or illness. It is generally reported as the number of new cases occurring within a certain period of time. For example, if over the course of a year, 10 women are diagnosed with breast cancer out of a total sample population of 200, the incidence rate of breast cancer in that population would be 5%. It can also be reported as a fraction of the population at risk of developing a disease (for example, the well-known statistic that one in two people will be diagnosed with cancer in their lifetime, giving an incidence rate of 0.5), and incidence rates can be further broken down according to different subsets of the population such as gender, race, or age group. Back to blogs written by GKA