We identified various types of prevalence studies.
The traditional prevalence studies (“core studies”) establish a rate based on the general population residing within a defined geographical area. In register-based studies these are typically the number of new cases in a defined catchment area (often health district, nation etc) over a certain period of time.
In other studies, the sample is from a specially defined group – such as migrants, cohorts born within restricted intervals, or others such as the deaf population – we report these separately as they can help identify differences in rates.