Editing Prevalence (section)

==Uses==

===Lifetime prevalence===
'''Lifetime prevalence'''<!--Redirects here, bolded per MOS:BOLD--> ('''LTP''') is the proportion of individuals in a population that at some point in their life (up to the time of assessment) have experienced a "case" (e.g., a disease, a traumatic event, or, a behavior, such as committing a crime). Often, a 12-month prevalence (or some other type of "period prevalence") is provided in conjunction with lifetime prevalence. ''Point prevalence'' is the prevalence of disorder at a specific point in time (a month or less). ''Lifetime morbid risk'' is "the proportion of a population that might become afflicted with a given disease at any point in their lifetime."<ref name="Rothman2012">{{cite book|author=Kenneth J. Rothman|title=Epidemiology: An Introduction|url=https://books.google.com/books?id=tKs7adtH-_IC&pg=PA53|date=21 June 2012|publisher=Oxford University Press|isbn=978-0-19-975455-7|page=53}}</ref><ref>{{Cite book| publisher = Oxford University Press| isbn = 978-0-19-937806-7| others = S. Charles Schulz, Michael Foster Green, Katharine J. Nelson (eds.)| title = Schizophrenia and psychotic spectrum disorders|chapter=Chapter 1: Overview of schizophrenia and treatment approaches|last1=Kruse|first1=Matthew|last2=Schulz|first2=S. Charles|page=7|location = New York|date = 2016}}</ref>

===Period prevalence===
'''Period prevalence'''<!--Redirects here, bolded per MOS:BOLD--> is the proportion of the population with a given disease or condition over a specific period of time. It could describe how many people in a population had a cold over the cold season in 2006, for example.{{cn|date=May 2023}} It is expressed as a percentage of the population and can be described by the following formula:

Period prevalence (proportion) = Number of cases that existed in a given period ÷ Number of people in the population during this period{{citation needed|date=June 2022}}

The relationship between incidence (rate), point prevalence (ratio) and period prevalence (ratio) is easily explained via an analogy with photography. Point prevalence is akin to a flashlit photograph: what is happening at this instant frozen in time. Period prevalence is analogous to a long exposure (seconds, rather than an instant) photograph: the number of events recorded in the photo whilst the camera shutter was open. In a movie each frame records an instant (point prevalence); by looking from frame to frame one notices new events (incident events) and can relate the number of such events to a period (number of frames); see [[Incidence (epidemiology)|incidence rate]].{{citation needed|date=June 2022}}

===Point prevalence===
'''Point prevalence'''<!--Redirects here, bolded per MOS:BOLD--> is a measure of the proportion of people in a population who have a disease or condition at a particular time, such as a particular date. It is like a snapshot of the disease in time. It can be used for statistics on the occurrence of [[chronic diseases]]. This is in contrast to period prevalence which is a measure of the proportion of people in a population who have a disease or condition over a specific period of time, say a season, or a year. Point prevalence can be described by the formula: Prevalence = Number of existing cases on a specific date ÷ Number of people in the population on this date <ref>
{{cite book|author=Gerstman, B.B.|year=2003|title=Epidemiology Kept Simple: An Introduction to Traditional and Modern Epidemiology (2nd ed.)|location=Hoboken, NJ|publisher=Wiley-Liss}}</ref>