Prevalensen

Prevalensen is the definite form of the epidemiological term prevalens in some Scandinavian languages, used to refer to the prevalence of a health condition or other attribute in a population at a given time. In epidemiology, prevalence denotes the proportion of individuals who have the condition at a specific moment or over a defined period, rather than the number of new cases.

There are several ways to describe prevalence. Point prevalence refers to the proportion of people with the condition at a single point in time. Period prevalence covers a specified interval, counting anyone who has the condition at any time during that period. Lifetime prevalence indicates the proportion who have ever had the condition by a certain age. Prevalence is commonly expressed as a percentage or as cases per a fixed number of people (for example, per 1,000 or 100,000).

Calculation and interpretation are straightforward but context matters. Prevalence is typically calculated as the number of existing cases at time t divided by the total population at time t. It reflects the combined effects of incidence, disease duration, recovery, and mortality, as well as migration and diagnostic practices. A high prevalence can indicate a large burden requiring more health resources, while a low prevalence may reflect either low incidence or a short duration of the condition.

Data sources for prevalensen include cross-sectional surveys, health registries, and electronic medical records. Limitations include diagnostic misclassification, underdiagnosis, sampling bias, and changes in population structure or case definitions over time.