prevalenties

Prevalenties, often referred to as prevalences, are epidemiological measures that describe how common a condition or attribute is in a population at a given time or over a defined period. They are expressed as a proportion and can be presented as percentages or per a defined population size. Prevalenties provide a snapshot of the burden of a condition and are used to compare disease or trait frequencies across populations and over time.

There are two main concepts: point prevalence and period prevalence. Point prevalence measures the proportion of individuals who have the condition at a specific moment. Period prevalence measures the proportion who have the condition at any time during a defined interval, which may include people who developed the condition and those who had it previously but still meet the case definition during the period. In both cases, the prevalence proportion is typically calculated as the number of existing cases divided by the total population at risk or in the population of interest, with standardizations applied as needed.

Prevalenties are influenced by incidence (the rate of new cases) and by the duration of the condition. They are commonly age-standardized to enable valid comparisons between populations with different age structures. Data sources include population surveys, clinical registries, and administrative records. Case definitions, data quality, and nonresponse can affect estimates.

In public health and medicine, prevalences are used to assess disease burden, plan resource allocation, monitor trends, and evaluate interventions. They are distinct from incidence, which tracks new cases over time, and should be interpreted in the context of duration, survival, and population characteristics.