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In science, prevalence describes a proportion (typically expressed as a percentage). For example, the prevalence of obesity among American adults in 2001 was estimated by the U. S. Centers for Disease Control (CDC) at approximately 20.9%. [5] Prevalence is a term that means being widespread and it is distinct from incidence.
Note that the PPV is not intrinsic to the test—it depends also on the prevalence. [2] Due to the large effect of prevalence upon predictive values, a standardized approach has been proposed, where the PPV is normalized to a prevalence of 50%. [11] PPV is directly proportional [dubious – discuss] to the prevalence of the disease or condition ...
The average lifetime prevalence found was 6.7% for MDD (with a relatively low lifetime prevalence rate in higher-quality studies, compared to the rates typically highlighted of 5–12% for men and 10–25% for women), and rates of 3.6% for dysthymia and 0.8% for Bipolar 1. [18]
Incidence is usually more useful than prevalence in understanding the disease etiology: for example, if the incidence rate of a disease in a population increases, then there is a risk factor that promotes the incidence. For example, consider a disease that takes a long time to cure and was widespread in 2002 but dissipated in 2003.
Epidemiology has its limits at the point where an inference is made that the relationship between an agent and a disease is causal (general causation) and where the magnitude of excess risk attributed to the agent has been determined; that is, epidemiology addresses whether an agent can cause disease, not whether an agent did cause a specific ...
DALYs = number of people with the disease × duration of the disease (or loss of life expectancy in the case of mortality) × severity (varying from 0 for perfect health to 1 for death) Necessary data include prevalence data, exposure-response relationships, and weighting factors that give an indication of the severity of a certain disorder ...
Sensitivity and specificity are prevalence-independent test characteristics, as their values are intrinsic to the test and do not depend on the disease prevalence in the population of interest. [6] Positive and negative predictive values , but not sensitivity or specificity, are values influenced by the prevalence of disease in the population ...
In epidemiology and actuarial science, the term morbidity (also morbidity rate or morbidity frequency) can refer to either the incidence rate, the prevalence of a disease or medical condition, or the percentage of people who experience a given condition within a given timeframe (e.g., 20% of people will get influenza in a year). [18]