title: Medical usage and abusage: "prevalence" and "incidence".
abstract: In view of the frequent misuse of the term "incidence," the concepts of incidence, prevalence, and period prevalence are defined and illustrated. The importance of restricting "incidence" to the rate of development of new events in a population or a group of patients, per unit of time, is stressed. Clearly distinguishing incidence from prevalence or simple proportion can help both in the understanding and the communication of findings in patient groups.
mesh_terms: D004813:Epidemiology; D010506:Periodicals as Topic; D009626:Terminology as Topic