WordNet

be a student; follow a course of study; be enrolled at an institute of learning
a room used for reading and writing and studying; "he knocked lightly on the closed door of the study"
applying the mind to learning and understanding a subject (especially by reading); "mastering a second language requires a lot of work"; "no schools offer graduate study in interior design" (同)work
a composition intended to develop one aspect of the performers technique; "a study in spiccato bowing"
a state of deep mental absorption; "she is in a deep study"
someone who memorizes quickly and easily (as the lines for a part in a play); "he is a quick study"
give careful consideration to; "consider the possibility of moving" (同)consider
learn by reading books; "He is studying geology in his room"; "I have an exam next week; I must hit the books now" (同)hit the books
think intently and at length, as for spiritual purposes; "He is meditating in his study" (同)meditate, contemplate
provide with or construct with studs; "stud the wall"
ornament consisting of a circular rounded protuberance (as on a vault or shield or belt) (同)rivet
poker in which each player receives hole cards and the remainder are dealt face up; bets are placed after each card is dealt (同)stud poker
adult male horse kept for breeding (同)studhorse
a man who is virile and sexually active (同)he-man, macho-man
a band of warriors (originally a unit of a Roman Legion)
a company of companions or supporters
small salmon of northern Pacific coasts and the Great Lakes (同)cohoe, coho_salmon, blue jack, silver_salmon, Oncorhynchus_kisutch

PrepTutorEJDIC

〈U〉(一般に)『勉強』,学習すること / 〈C〉(…の)勉強,研究《+of+名》 / 〈C〉〈U〉(…の)『綿密な調査』,検討《+of+名》 / 〈C〉研究対象(問題,事項);学科 / 〈C〉『書斎』,勉強部屋 / 〈C〉(美術・文学などの)習作,試作,スケッチ,(音楽の)練習曲,エチュード / …‘を'『勉強する』,学ぶ,研究する / …‘を'『よく注意して見る』,しげしげと見る / …‘を'『調査する』,検討する / …‘を'考慮する,配慮する / 〈せりふなど〉‘を'覚えようとする / 『勉強する』,学ぶ,研究する
《おもに米》種馬 / 《集合的に》(一群の)繁殖用動物(種馬,種牛など)
(インテリアなどに用いる)飾りびょう / カフスボタン,カラーボタン / (建物の)間柱 / (…を)…‘に'ちりばめる《+名+with+名》 / …‘に'点在(散在)している / …‘に'間柱をつける
(古代ローマの)歩兵隊(1隊が300‐600人で,10隊で1軍団(legion)となる) / 群,グループ,一団 / 《米》(悪い意味で)仲間,兄弟分

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/06/19 12:15:00」(JST)

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A cohort study is a form of longitudinal study (a type of observational study) used in medicine, nursing, social science, actuarial science, business analytics, and ecology. For instance in medicine, it is an analysis of risk factors and follows a group of people who do not have the disease, and uses correlations to determine the absolute risk of subject contraction. It is one type of clinical study design and should be compared with a cross-sectional study. Cohort studies are largely about the life histories of segments of populations, and the individual people who constitute these segments.^[1]^[2]

A cohort is a group of people who share a common characteristic or experience within a defined period (e.g., are born, are exposed to a drug or vaccine or pollutant, or undergo a certain medical procedure). Thus a group of people who were born on a day or in a particular period, say 1948, form a birth cohort. The comparison group may be the general population from which the cohort is drawn, or it may be another cohort of persons thought to have had little or no exposure to the substance under investigation, but otherwise similar. Alternatively, subgroups within the cohort may be compared with each other.

Randomized controlled trials (RCTs) are a superior methodology in the hierarchy of evidence in therapy, because they limit the potential for any biases by randomly assigning one patient pool to an intervention and another patient pool to non-intervention (or placebo). This minimizes the chance that the incidence of confounding (particularly unknown confounding) variables will differ between the two groups. However, it is important to note that RCTs may not be suitable in all cases and other methodologies could be much more suitable to investigate the study's objective(s).

Cohort studies can either be conducted prospectively, or retrospectively from archived records.^[3]

Application

In medicine, a cohort study is often undertaken to obtain evidence to try to refute the existence of a suspected association between cause and effect; failure to refute a hypothesis often strengthens confidence in it. Crucially, the cohort is identified before the appearance of the disease under investigation. The study groups follow a group of people who do not have the disease for a period of time and see who develops the disease (new incidence). The cohort cannot therefore be defined as a group of people who already have the disease. Prospective (longitudinal) cohort studies between exposure and disease strongly aid in studying causal associations, though distinguishing true causality usually requires further corroboration from further experimental trials.

The advantage of prospective cohort study data is that it can help determine risk factors for contracting a new disease because it is a longitudinal observation of the individual through time, and the collection of data at regular intervals, so recall error is reduced. However, cohort studies are expensive to conduct, are sensitive to attrition and take a long follow-up time to generate useful data. Nevertheless, the results that are obtained from long-term cohort studies are of substantially superior quality to those obtained from retrospective/cross-sectional studies. Prospective cohort studies are considered to yield the most reliable results in observational epidemiology. They enable a wide range of exposure-disease associations to be studied.

Some cohort studies track groups of children from their birth, and record a wide range of information (exposures) about them. The value of a cohort study depends on the researchers' capacity to stay in touch with all members of the cohort. Some studies have continued for decades.

In a cohort study, the population under investigation consists of individuals who are at risk of developing a specific disease or health outcome.^[4]

Examples

An example of an epidemiological question that can be answered using a cohort study is: does exposure to X (say, smoking) associate with outcome Y (say, lung cancer)? Such a study would recruit a group of smokers and a group of non-smokers (the unexposed group) and follow them for a set period of time and note differences in the incidence of lung cancer between the groups at the end of this time. The groups are matched in terms of many other variables such as economic status and other health status so that the variable being assessed, the independent variable (in this case, smoking) can be isolated as the cause of the dependent variable (in this case, lung cancer). In this example, a statistically significant increase in the incidence of lung cancer in the smoking group as compared to the non-smoking group is evidence in favor of the hypothesis. However, rare outcomes, such as lung cancer, are generally not studied with the use of a cohort study, but are rather studied with the use of a case-control study.

Shorter term studies are commonly used in medical research as a form of clinical trial, or means to test a particular hypothesis of clinical importance. Such studies typically follow two groups of patients for a period of time and compare an endpoint or outcome measure between the two groups.

Randomized controlled trials, or RCTs are a superior methodology in the hierarchy of evidence, because they limit the potential for bias by randomly assigning one patient pool to an intervention and another patient pool to non-intervention (or placebo). This minimizes the chance that the incidence of confounding variables will differ between the two groups.

Nevertheless, it is sometimes not practical or ethical to perform RCTs to answer a clinical question. To take our example, if we already had reasonable evidence that smoking causes lung cancer then persuading a pool of non-smokers to take up smoking in order to test this hypothesis would generally be considered quite unethical.

Two examples of cohort studies that have been going on for more than 50 years are the Framingham Heart Study and the National Child Development Study (NCDS), the most widely-researched of the British birth cohort studies. Key findings of NCDS and a detailed profile of the study appear in the International Journal of Epidemiology.^[5]

The largest cohort study in women is the Nurses' Health Study. Started in 1976, it is tracking over 120,000 nurses and has been analyzed for many different conditions and outcomes.

The largest cohort study in Africa is the Birth to Twenty Study, which began in 1990 and tracks a cohort of over 3,000 children born in the weeks following Nelson Mandela's release from prison.

Other famous examples are the Grant Study tracking a number of Harvard graduates from ca. 1950.77, the Whitehall Study tracking 10,308 British civil servants, and the Caerphilly Heart Disease Study, which since 1979 has studied a representative sample of 2,512 men, drawn from the Welsh town of Caerphilly.^[6]

Variations

Comparison of timelines of case-control and cohort studies

The diagram indicates the starting point and direction of cohort and case-control studies. In Case-control studies the analysis proceeds from documented disease and investigations are made to arrive at the possible causes of the disease. In cohort studies the assessments starts with the putative cause of disease, and observations are made of the occurrence of disease relative to the hypothesized causal agent.^[7]

Current and historical cohorts

A current cohort study represents a true prospective study where the data concerning exposure are assembled prior to the occurrence of the fact to be studied, for instance a disease. An example of a current cohort study is the Oxford Family Planning Association Study in the United Kingdom, which aimed to provide a balanced view of the beneficial and harmful effects of different methods of contraception. This study has provided a large amount of information on the efficacy and safety of contraceptive methods, and in particular oral contraceptives (OCs), diaphragms and intrauterine device (IUDs).^{[citation needed]}

In a historical cohort study the data concerning exposure and occurrence of a disease, births, a political attitude or any other categorical variable are collected after the events have taken place, and the subjects (those exposed and unexposed to the agent under study) are assembled from existing records or health care registers.

A "prospective cohort" defines the groups before the study is done, while historical studies, which are sometimes referred to as "retrospective cohort", defines the grouping after the data is collected. Examples of a retrospective cohort are Long-Term Mortality after Gastric Bypass Surgery^[8] and The Lothian Birth Cohort Studies.^[9]

Though historical studies are sometimes referred to as retrospective study, it a misnomer as the methodological principles of historical cohort studies and prospective studies are the same.^[7]

Nested case-control study

An example of a nested case-control study is Inflammatory markers and the risk of coronary heart disease in men and women, which was a case control analyses extracted from the Framingham Heart Study cohort.^[10]

Household panel survey

Household panel surveys are an important sub-type of cohort study. These draw representative samples of households and survey them, following all individuals through time on a usually annual basis. Examples include the US Panel Study of Income Dynamics (since 1968), the German Socio-Economic Panel (since 1984), the British Household Panel Survey (since 1991), the Household, Income and Labour Dynamics in Australia Survey (since 2001) and the European Community Household Panel (1994–2001).

Cohort analysis in business

For an example in business analysis, see cohort analysis.

References

^ "Cohort Studies". Web Center for Social Research Methods. Archived from the original on 2011-09-09.
^ Porta, Miquel, ed. (2008). A Dictionary of Epidemiology (5th ed.). New York: Oxford University Press.
^ "FAQ: What is a cohort study?". California Department of Public Health, Environmental Health Investigations Branch. June 2, 2001.
^ Blumenthal, Ursula J.; Fleisher, Jay M.; Esrey, Steve A.; Peasey, Anne (2001). "Chapter 7: Epidemiology: a tool for the assessment of risk" (PDF). In Fewtrell, Lorna; Bartram, Jamie. Water Quality: Guidelines, Standards, and Health : Assessment of Risk and Risk Management for Water-related Infectious Disease. IWA Publishing. pp. 143–144.
^ Power C and Elliott J (2006). "Cohort profile: 1958 British Cohort Study". International Journal of Epidemiology 35 (1): 34–41. doi:10.1093/ije/dyi183. PMID 16155052.
^ The Caerphilly and Speedwell Collaborative Group. (1984 September). "Caerphilly and Speedwell collaborative heart disease studies.". Journal of Epidemiology and Public Health 38 (3): 259–262. PMID 6332166 PMC 1052363.
^ ^a ^b Meirik, O. "Cohort and Case-Control Studies". In Campana, Aldo. Reproductive Health. Geneva Foundation for Medical Education and Research.
^ Adams TD; Gress RE; Smith SC et al. (2007). "Long-term mortality after gastric bypass surgery". N. Engl. J. Med. 357 (8): 753–61. doi:10.1056/NEJMoa066603. PMID 17715409.
^ "The Lothian Birth Cohort Studies". University of Edinburgh. Archived from the original on 2009-10-22. Retrieved 8 May 2011.
^ Pai, JK; Pischon, T; Ma, J et al. (2004). "Inflammatory markers and the risk of coronary heart disease in men and women". N. Engl. J. Med. 351 (25): 2599–2610. doi:10.1056/NEJMoa040967. PMID 15602020.

External links

Prospective cohorts
Retrospective cohorts
Study Design Tutorial Cornell University College of Veterinary Medicine
Birth cohort study timelines (ESDS Longitudinal)
Centre for Longitudinal Studies

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Economic stressors and alcohol-related outcomes: Exploring age cohort differences.

Brown RL1, Richman JA2, Rospenda KM3.
Addictive behaviors.Addict Behav.2015 Dec;51:193-6. doi: 10.1016/j.addbeh.2015.07.016. Epub 2015 Jul 26.
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Audrain-McGovern J1, Rodriguez D2.
Addictive behaviors.Addict Behav.2015 Dec;51:177-83. doi: 10.1016/j.addbeh.2015.07.032. Epub 2015 Aug 1.
OBJECTIVE: Research has documented that physical activity is associated with a lower risk of adolescent smoking uptake, yet it is unclear whether this relationship exists for all types of physical activity. We sought to determine whether certain types of physical activity are associated with a decre
PMID 26280377

A social network analysis approach to alcohol use and co-occurring addictive behavior in young adults.

Meisel MK1, Clifton AD2, MacKillop J3, Goodie AS4.
Addictive behaviors.Addict Behav.2015 Dec;51:72-9. doi: 10.1016/j.addbeh.2015.07.009. Epub 2015 Jul 21.
INTRODUCTION: The current study applied egocentric social network analysis (SNA) to investigate the prevalence of addictive behavior and co-occurring substance use in college students' networks. Specifically, we examined individuals' perceptions of the frequency of network members' co-occurring addi
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Japanese Journal

Are regional variations in activity of dispatcher-assisted cardiopulmonary resuscitation associated with out-of-hospital cardiac arrests outcomes? A nation-wide population-based cohort study

Resuscitation 98, 27-34, 2016-01-01
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Predictors for chronic neck and low back pain in office workers : a 1-year prospective cohort study

Journal of Occupational Health 58(1), 16-24, 2016-01
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新しいコホート研究の立ち上げと今後の展望 : 神戸研究と鶴岡メタボロームコホート研究 (特集わが国における脳・心血管疾患予防のための疫学研究)

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Related Pictures

★リンクテーブル★

リンク元	「コホート研究」
拡張検索	「prospective cohort study」「retrospective cohort study」
関連記事	「study」「stud」「cohort」

「コホート研究」

　　[★]

英: cohort study
関: 研究デザイン、コホート内症例対照研究

観察研究

分析疫学

定義

対照集団を要因の有無別に分けて、疾病罹患の傾向を比較する
ある時点で研究対象を決めて、その人たちを追跡調査するスタイルの研究

なんらかの共通特性をもった人たちと、その特性をもっていない人たちを追跡調査し、疾病の発症率を調べることで、特性の有無が疾病の発生リスクにどのような効果をもつかを直接計算できる。(http://phi.med.gunma-u.ac.jp/epi-spc/term4.pdf)

種類

前向きコホート研究 (Prospective Cohort Study)
後ろ向きコホート研究 (Retrospective Cohort Study)

特徴

	名称	患者対照研究	コホート研究
	時間軸	後向き研究	前向き研究
	調査の方法	既往調査、病歴調査	追跡調査
対象	曝露情報の信頼性	患者の過去の記録やカルテに頼るため信頼性は低い	現時点での曝露状況が判明しているので信頼性は高い
対象	偏りバイアス	抽出の段階で、既に患者、対照群ともに偏りが発生している場合が多い	母集団から、要因の有無別に対照群が抽出されるため、偏りは小さい
対象	まれな要因	評価不能	評価可能
調査	観察期間	なし	長期
調査	費用労力	患者と対照のみを観察するので、費用・労力が少ない	大きな集団を長期に追跡しなければならないので、費用・労力が多い
疾患	対照疾患	単一	複数
疾患	診断の正確性	正確性が高い	正確性が低い →診断基準が必要
疾患	まれな疾患	可能	困難
解析	罹患率	計算不可	算出可能
解析	相対危険度	近似値の算出	算出可能
解析	寄与危険度	計算不可	算出可能