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Updated June 13, 2014

Definition: Prevalence and incidence are both terms that are commonly used to refer to measurements of disease frequency. Incidence is defined elsewhere.

The prevalence of a disease is the proportion of a population that is affected by the disease at a specific time. For example, the prevalence of celiac disease in Finland from 1978 to 1980 was 1.05%.

Prevalence is an appropriate measure only for relatively stable, chronic conditions, not for acute diseases, such as flu or measles.

Even in a chronic condition, such as back pain, the problems can be intermittent. Therefore, calculating the prevalence based on a single examination of everyone in the population at one point in time will probably underestimate the true prevalence of back pain. (This type of assessment is known as “point prevalence.”) Instead, it’s better to perform repeated or continuous assessments of the same population over a longer period, such as 12 months or more.


Epidemiology for the Uninitiated, 4th ed. Coggon D et al, Editors. Published by the British Medical Journal.

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