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Case–control Study
A case–control study (also known as case–referent study) is a type of observational study in which two existing groups differing in outcome are identified and compared on the basis of some supposed causal attribute. Case–control studies are often used to identify factors that may contribute to a medical condition by comparing subjects who have that condition/disease (the "cases") with patients who do not have the condition/disease but are otherwise similar (the "controls"). They require fewer resources but provide less evidence for causal inference than a randomized controlled trial. A case–control study produces only an odds ratio, which is an inferior measure of strength of association compared to relative risk. Definition The case–control is a type of epidemiological observational study. An observational study is a study in which subjects are not randomized to the exposed or unexposed groups, rather the subjects are ''observed'' in order to determine both their expo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Richard Doll
Sir William Richard Shaboe Doll (28 October 1912 – 24 July 2005) was a British physician who became an epidemiologist in the mid-20th century and made important contributions to that discipline. He was a pioneer in research linking smoking to health problems. With Ernst Wynder, Bradford Hill and Evarts Graham, he was credited with being the first to prove that smoking increased the risk of :lung cancer and :heart disease. (German studies had suggested a link as early as the 1920s but were forgotten or ignored until the 1990s.) He also carried out pioneering work on the relationship between radiation and leukaemia as well as that between asbestos and lung cancer, and alcohol and breast cancer. On 28 June 2012, he was the subject of an episode of ''The New Elizabethans'', a series broadcast on BBC Radio Four to mark the Diamond Jubilee of Queen Elizabeth II, dealing with 60 public figures from her reign. Biography Doll was born at Hampton, Middlesex (now part of south-wes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epidemiology
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population. It is a cornerstone of public health, and shapes policy decisions and evidence-based practice by identifying risk factors for disease and targets for preventive healthcare. Epidemiologists help with study design, collection, and statistical analysis of data, amend interpretation and dissemination of results (including peer review and occasional systematic review). Epidemiology has helped develop methodology used in clinical research, public health studies, and, to a lesser extent, basic research in the biological sciences. Major areas of epidemiological study include disease causation, transmission, outbreak investigation, disease surveillance, environmental epidemiology, forensic epidemiology, occupational epidemiology, screening, biomonitoring, and comparisons of treatment effects such as in clinical t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prospective Cohort Study
A prospective cohort study is a longitudinal cohort study that follows over time a group of similar individuals (cohorts) who differ with respect to certain factors under study, to determine how these factors affect rates of a certain outcome. For example, one might follow a cohort of middle-aged truck drivers who vary in terms of smoking habits, to test the hypothesis that the 20-year incidence rate of lung cancer will be highest among heavy smokers, followed by moderate smokers, and then nonsmokers. The prospective study is important for research on the etiology of diseases and disorders. The distinguishing feature of a prospective cohort study is that at the time that the investigators begin enrolling subjects and collecting baseline exposure information, none of the subjects have developed any of the outcomes of interest. After baseline information is collected, subjects in a prospective cohort study are then followed "longitudinally," i.e. over a period of time, usually for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retrospective Cohort Study
A retrospective cohort study, also called a historic cohort study, is a longitudinal cohort study used in medical and psychological research. A cohort of individuals that share a common exposure factor is compared with another group of equivalent individuals not exposed to that factor, to determine the factor's influence on the incidence of a condition such as disease or death. Retrospective cohort studies have existed for approximately as long as prospective cohort studies. Design The retrospective cohort study compares groups of individuals who are alike in many ways but differ by a certain characteristic (for example, female nurses who smoke and ones who do not smoke) in terms of a particular outcome (such as lung cancer). Data on the relevant events for each individual (the form and time of exposure to a factor, the latent period, and the time of any subsequent occurrence of the outcome) are collected from existing records and can immediately be analyzed to determine the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nested Case–control Study
A nested case–control (NCC) study is a variation of a case–control study in which cases and controls are drawn from the population in a fully enumerated cohort. Usually, the exposure of interest is only measured among the cases and the selected controls. Thus the nested case–control study is more efficient than the full cohort design. The nested case–control study can be analyzed using methods for missing covariates. The NCC design is often used when the exposure of interest is difficult or expensive to obtain and when the outcome is rare. By utilizing data previously collected from a large cohort study, the time and cost of beginning a new case–control study is avoided. By only measuring the covariate in as many participants as necessary, the cost and effort of exposure assessment is reduced. This benefit is pronounced when the covariate of interest is biological, since assessments such as gene expression profiling are expensive, and because the quantity of blood availabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Randomized Controlled Trial
A randomized controlled trial (or randomized control trial; RCT) is a form of scientific experiment used to control factors not under direct experimental control. Examples of RCTs are clinical trials that compare the effects of drugs, surgical techniques, medical devices, diagnostic procedures or other medical treatments. Participants who enroll in RCTs differ from one another in known and unknown ways that can influence study outcomes, and yet cannot be directly controlled. By randomly allocating participants among compared treatments, an RCT enables ''statistical control'' over these influences. Provided it is designed well, conducted properly, and enrolls enough participants, an RCT may achieve sufficient control over these confounding factors to deliver a useful comparison of the treatments studied. Definition and examples An RCT in clinical research typically compares a proposed new treatment against an existing standard of care; these are then termed the 'experimental' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archie Cochrane
Archibald Leman Cochrane (12 January 1909 – 18 June 1988) was a Scottish doctor noted for his book ''Effectiveness and Efficiency: Random Reflections on Health Services''. This book advocated the use of randomized control trials to make medicine more effective and efficient. His advocacy of randomized controlled trials eventually led to the development of the Cochrane Library database of systematic reviews, the establishment of the UK Cochrane Centre in Oxford and the international organisation Cochrane. He is known as one of the fathers of modern clinical epidemiology and evidence-based medicine and is considered to be the originator of the idea of evidence-based medicine in the current era. Biography Cochrane was born in Kirklands, Galashiels, Scotland, into a family he described as "industrial upper middle class". His father was killed whilst serving with the King's Own Scottish Borderers during World War I. He won a scholarship to Uppingham School, and obtained another ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Philip E
Philip, also Phillip, is a male given name, derived from the Greek (''Philippos'', lit. "horse-loving" or "fond of horses"), from a compound of (''philos'', "dear", "loved", "loving") and (''hippos'', "horse"). Prominent Philips who popularized the name include kings of Macedonia and one of the apostles of early Christianity. ''Philip'' has many alternative spellings. One derivation often used as a surname is Phillips. It was also found during ancient Greek times with two Ps as Philippides and Philippos. It has many diminutive (or even hypocoristic) forms including Phil, Philly, Lip, Pip, Pep or Peps. There are also feminine forms such as Philippine and Philippa. Antiquity Kings of Macedon * Philip I of Macedon * Philip II of Macedon, father of Alexander the Great * Philip III of Macedon, half-brother of Alexander the Great * Philip IV of Macedon * Philip V of Macedon New Testament * Philip the Apostle * Philip the Evangelist Others * Philippus of Croton (c. 6th c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Incidence Rate Ratio
In epidemiology, a rate ratio, sometimes called an incidence density ratio or incidence rate ratio, is a relative difference measure used to compare the incidence rates of events occurring at any given point in time. It is defined as: : \text = \frac where incidence rate is the occurrence of an event over person-time (for example person-years): : \text = \frac The same time intervals must be used for both incidence rates. A common application for this measure in analytic epidemiologic studies is in the search for a causal association between a certain risk factor and an outcome. See also *Odds ratio *Ratio In mathematics, a ratio shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ... * Risk ratio References Biostatistics Epidemiology Rates {{statistics-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rare Disease Assumption
The rare disease assumption is a mathematical assumption in epidemiologic case-control studies where the hypothesis tests the association between an exposure and a disease. It is assumed that, if the prevalence of the disease is low, then the odds ratio (OR) approaches the relative risk (RR). The idea was first demonsterated by Jerome Cornfield. Case control studies are relatively inexpensive and less time-consuming than cohort studies. Since case control studies don't track patients over time, they can't establish relative risk. The case control study can, however, calculate the exposure-odds ratio, which, mathematically, is supposed to approach the relative risk as prevalence falls. Sander Greenland showed that if the prevalence is 10% or less, the disease can be considered rare enough to allow the rare disease assumption. Unfortunately, the magnitude of discrepancy between the odds ratio and the relative risk is dependent not only on the prevalence, but also, to a great de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Austin Bradford Hill
Sir Austin Bradford Hill (8 July 1897 – 18 April 1991) was an English epidemiologist and statistician, pioneered the randomised clinical trial and, together with Richard Doll, demonstrated the connection between cigarette smoking and lung cancer. Hill is widely known for pioneering the "Bradford Hill" criteria for determining a causal association. Early life Hill was born in London, son of Sir Leonard Erskine Hill FRS, a distinguished physiologist, and Janet Alexander. He was the grandson of noted scholar George Birkbeck Hill. As a child he lived at the family home, Osborne House, Loughton, Essex; he was educated at Chigwell School, Essex. He served as a pilot in the First World War but was invalided out when he contracted tuberculosis. Two years in hospital and two years of convalescence put a medical qualification out of the question and he took a degree in economics by correspondence at London University. Career In 1922, Hill went to work for the Industry Fatigue Re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
