WordNet

be worthy of or have a certain rating; "This bond rates highly"
amount of a charge or payment relative to some basis; "a 10-minute phone call at that rate would cost $5" (同)charge per unit
a magnitude or frequency relative to a time unit; "they traveled at a rate of 55 miles per hour"; "the rate of change was faster than expected"
a quantity or amount or measure considered as a proportion of another quantity or amount or measure; "the literacy rate"; "the retention rate"; "the dropout rate"
assign a rank or rating to; "how would you rank these students?"; "The restaurant is rated highly in the food guide" (同)rank, range, order, grade, place
estimate the value of; "How would you rate his chances to become President?"; "Gold was rated highly among the Romans" (同)value
give (hair) the appearance of being fuller by using a rat
a pad (usually made of hair) worn as part of a womans coiffure
any of various long-tailed rodents similar to but larger than a mouse
catch rats, especially with dogs
desert ones party or group of friends, for example, for ones personal advantage
employ scabs or strike breakers in
(epidemiology) the ratio (for a given time period) of the number of occurrences of a disease or event to the number of units at risk in the population
the quality of prevailing generally; being widespread; "he was surprised by the prevalence of optimism about the future"
standing or position on a scale
a local tax on property (usually used in the plural)

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〈C〉『割合』,『率』 / 〈C〉《the~,a~》『速度』(speed),進度 / 〈C〉『値段』,『相場』;料金 / 〈U〉等級(class),(…)等 / 《複数形ぃ》《英》地方税 / (…の金額に)…‘の'『値段を決める』,見積もる《+『名』+『at』+『名』》 / …‘を'『評価する』,みなす / 《米話》…‘に'値する,‘の'価値がある / 『評価される』;みなされる
…‘を'どなりつける
『ネズミ』 / ひきょう者,裏切り者 / ネズミをつかまえる / 《話》(人を)裏切る,密告する《+『on』+『名』〈人〉》
広く行きわっていること,普及 / 優勢,支配
〈C〉〈U〉（品質・技量などによる）格づけ,評価 / 〈C〉（個人・会社の経済的な）信用度 / 〈C〉(トン・馬力による)(船舶・車)の等級 / 〈C〉(テレビ・ラジオの)視聴率

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/05/14 01:57:44」(JST)

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Prevalence or prevalence proportion, in epidemiology, is the proportion of a population found to have a condition (typically a disease or a risk factor such as smoking or seat-belt use). It is arrived at by comparing the number of people found to have the condition with the total number of people studied, and is usually expressed as a fraction, as a percentage or as the number of cases per 10,000 or 100,000 people. "Point prevalence" is the proportion of a population that has the condition at a specific point in time. "Period prevalence" is the proportion of a population that has the condition at some time during a given period ("12-month prevalence", etc.), and includes people who already have the condition at the start of the study period as well as those who acquire it during that period. "Lifetime prevalence" (LTP) is the proportion of a population that at some point in their life (up to the time of assessment) have experienced the condition.^[1]

Prevalence estimates are used by epidemiologists, health care providers, government agencies, and insurers.

Prevalence is contrasted with incidence, which is a measure of new cases arising in a population over a given period (month, year, etc.). The difference between prevalence and incidence can be summarized thus: prevalence answers "How many people have this disease right now?" and incidence answers "How many people per year newly acquire this disease?".

Examples and utility

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%.^[2]

Prevalence is a term which means being widespread and it is distinct from incidence. Prevalence is a measurement of all individuals affected by the disease at a particular time, whereas incidence is a measurement of the number of new individuals who contract a disease during a particular period of time.

To illustrate, a long term disease that was spread widely in a community in 2002 will have a high prevalence at a given point of 2003 (assuming it has a long duration) but it might have a low incidence rate during 2003 (i.e. lots of existing cases, but not many new ones in that year). Conversely, a disease that is easily transmitted but has a short duration might spread widely during 2002 but is likely to have a low prevalence at any given point in 2003 (due to its short duration) but a high incidence during 2002 (as many people develop the disease). As such, prevalence is a useful parameter when talking about long lasting diseases, such as HIV, but incidence is more useful when talking about diseases of short duration, such as chickenpox.

Uses

Lifetime prevalence

Lifetime prevalence (LTP) is the number of individuals in a statistical population that at some point in their life (up to the time of assessment) have experienced a "case" (e.g., a disorder), compared to the total number of individuals (i.e. it is expressed as a ratio or percentage). Often, a 12-month prevalence (or some other type of "period prevalence") is used in conjunction with lifetime prevalence. There is also point prevalence, the prevalence of disorder at a more specific (a month or less) point in time. There is also a related figure lifetime morbid risk - the theoretical prevalence at any point in life for anyone, regardless of time of assessment.

Period prevalence

In epidemiology, Period prevalence 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. It is expressed as a percentage of the population and can be described by the following formula:

Period prevalence (ratio) = Number of cases that occurred in a given period ÷ Number of people in the population during this period

The relationship between incidence (rate), point prevalence (ratio) and period prevalence (ratio) is easily explicated 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 rate.

Point prevalence

In epidemiology, point prevalence 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 snap shot 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 ^[3]

Limitations

It can be said that a very small error applied over a very large number of individuals (that is, those who are not affected by the condition in the general population during their lifetime; for example, over 95%) produces a relevant, non-negligible number of subjects who are incorrectly classified as having the condition or any other condition which is the object of a survey study: these subjects are the so-called false positives; such reasoning applies to the 'false positive' but not the 'false negative' problem where we have an error applied over a relatively very small number of individuals to begin with (that is, those who are affected by the condition in the general population; for example, less than 5%). Hence, a very high percentage of subjects who seem to have a history of a disorder at interview are false positives for such a medical condition and apparently never suffered a fully clinical syndrome.

A different but related problem in evaluating the public health significance of psychiatric conditions has been highlighted by Robert Spitzer of Columbia University: fulfillment of diagnostic criteria and the resulting diagnosis do not necessarily imply need for treatment.^[4]

A well-known statistical problem arises when ascertaining rates for disorders and conditions with a relatively low population prevalence or base rate. Even assuming that lay interview diagnoses are highly accurate in terms of sensitivity and specificity and their corresponding area under the ROC curve (that is, AUC, or area under the receiver operating characteristic curve), a condition with a relatively low prevalence or base-rate is bound to yield high false positive rates, which exceed false negative rates; in such a circumstance a limited positive predictive value, PPV, yields high false positive rates even in presence of a specificity which is very close to 100%.^[5]

References

^ Kenneth J. Rothman (21 June 2012). Epidemiology: An Introduction. Oxford University Press. p. 53. ISBN 978-0-19-975455-7.
^ http://www.cdc.gov/nccdphp/dnpa/obesity/trend/prev_reg.htm
^ Gerstman, B.B. (2003). Epidemiology Kept Simple: An Introduction to Traditional and Modern Epidemiology (2nd ed.). Hoboken, NJ: Wiley-Liss.
^ Spitzer, Robert (February 1998). "Diagnosis and need for treatment are not the same". Archives of General Psychiatry 55 (2): 120. doi:10.1001/archpsyc.55.2.120. PMID 9477924.
^ Baldessarini, Ross J.; Finklestein S.; Arana G. W. (May 1983). "The predictive power of diagnostic tests and the effect of prevalence of illness". Archives of General Psychiatry 40 (5): 569–73. doi:10.1001/archpsyc.1983.01790050095011. PMID 6838334.

External links

PlusNews, the UN's HIV/AIDS news service provides HIV prevalence rates for nearly 60 countries worldwide
Synopsis of article on "How Prevalent Is Schizophrenia?" from Public Library of Science

UpToDate Contents

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English Journal

Impact of residual ethmoid cells on postoperative course after endoscopic sinus surgery for chronic rhinosinusitis.

Okushi T, Mori E, Nakayama T, Asaka D, Matsuwaki Y, Ota K, Chiba S, Moriyama H, Otori N.SourceDepartment of Otorhinolaryngology, Jikei University School of Medicine, Japan.
Auris, nasus, larynx.Auris Nasus Larynx.2012 Oct;39(5):484-9. Epub 2011 Nov 15.
OBJECTIVE: Endoscopic sinus surgery (ESS) is a worldwide standard surgical procedure for chronic rhinosinusitis (CRS). Residual ethmoid cells (RECs), which result from failure to completely remove them, have been thought to be a cause of recurrence of CRS. Our objective was to investigate the relati
PMID 22088258

Work-related injuries and musculoskeletal disorders among factory workers in a major city of China.

Yu W, Yu IT, Li Z, Wang X, Sun T, Lin H, Wan S, Qiu H, Xie S.SourceChina Center for Disease Control and Prevention, No. 27 Nanwei Road, 100050, Beijing, China.
Accident; analysis and prevention.Accid Anal Prev.2012 Sep;48:457-63. Epub 2012 Mar 27.
This study describes the frequency of occurrence of work-related injuries and musculoskeletal disorders (MSDs) among factory workers in Shenzhen, China, and examines the determinants of injuries and MSDs. A cross-sectional survey was conducted with 3479 frontline workers in 60 factories during 2008-
PMID 22664712

Japanese Journal

The prevalence of falling and status of physical function among elderly individuals with locomotive and visual/hearing disorders

Demura Shinichi,Sato Susumu,Mitsumori Atsuko,Sato Toshiro
Archives of Gerontology and Geriatrics 57(3), 333-338, 2013-12
… This study aimed to examine the relationship between these disorders and the prevalence rates for falling and physical function status. … Although there was no significant odds ratio in the presence of multiple disorders, the prevalence rate of the multiple disorders increased with age and this increased the risk of falling also increases with age. …
NAID 120005302298

The prevalence of falling and status of physical function among elderly individuals with locomotive and visual/hearing disorders

Demura Shinichi,Sato Susumu,Mitsumori Atsuko,Sato Toshiro
Archives of Gerontology and Geriatrics 57(3), 333-338, 2013-11
… This study aimed to examine the relationship between these disorders and the prevalence rates for falling and physical function status. … Although there was no significant odds ratio in the presence of multiple disorders, the prevalence rate of the multiple disorders increased with age and this increased the risk of falling also increases with age. …
NAID 120005327244

コミュニティセンター「かながわレインボーセンターSHIP」の夜間HIV/STIs即日検査相談を受けたMSM(men who have sex with men)の特徴及び罹患率

井戸田一朗,星野慎二,沢田貴志 [他]
日本公衆衛生雑誌 = Japanese journal of public health 60(5), 253-261, 2013-05
NAID 40019650407

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★リンクテーブル★

リンク元	「疾患と死亡に関わる疫学指標」「有病率」
関連記事	「rate」「prevalence」「rat」

「疾患と死亡に関わる疫学指標」

　　[★]

		定義	特徴	式
罹患率	incidence rate	単位人口(暴露人口、危険人口)に対する一定期間内に新たに疾病異常者となった者の割合	動的	一定の観察期間内に新規発生した患者数 [人] / 危険暴露人口一人一人の観察期間の総和 [人年]
有病率	prevalence rate	単位人口に対する一時点における疾病異常者の割合	静的	集団のある一時点における疾病を有する者の数[人] / 集団の調査対象全員の数[人]
死亡率	mortality rate	単位人口に対する一定期間内における死亡数の割合		集団のある一定期間内における死亡者数[人] / 集団の調査対象全員の数[人]
致命率	case fatality rate	一定期間内において、対象とする疾患にかかった者がその疾患で死亡する者の割合	急性疾患の重篤度を表す。	死亡率 / 罹患率
生存率	survival rate	対象とする疾患に罹患しているのものが、一定期間中に死亡から免れる確率	慢性疾患の予後判定に用いられる。	(1-死亡率)の積和