Experimental epidemiology

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Experimental epidemiology is a type of epidemiological investigation that uses an experimental model to confirm a causal relationship suggested by observational studies. It studies the relationships of various factors determining the frequency and distribution of diseases in a community. [1] [2]

Contents

Case types

There are three case types in experimental epidemiology: randomized controlled trial, typically used for new medicine or drug testing; field trial, which is conducted on those at high risk of contracting a disease; and community trial, in which research is conducted on an entire community or neighborhood. [1] Randomized controlled trial determines the efficacy of a particular treatment, while other trials may be preventive intervention. [3]

Method

Experimental epidemiology employs prospective population experiments designed to test epidemiological hypotheses, and usually attempts to relate the postulated cause to the observed effect. Trials of new anthelmintics are an example. [1] Intervention or experimentation involves attempting to change a variable in one or more groups of people. This could mean eliminating a dietary factor thought to cause allergy, or testing a new treatment on a selected group of patients. The effects of an intervention are measured by comparing the result in the experimental group with that in a control group. [4]

See also

Related Research Articles

Design of experiments method and a specialization in statistics

The design of experiments is the design of any task that aims to describe or explain the variation of information under conditions that are hypothesized to reflect the variation. The term is generally associated with experiments in which the design introduces conditions that directly affect the variation, but may also refer to the design of quasi-experiments, in which natural conditions that influence the variation are selected for observation.

Epidemiology is the study and analysis of the distribution, patterns and determinants of health and disease conditions in defined populations.

Randomized controlled trial experimental method designed to reduce bias

A randomized controlled trial is a type of scientific experiment that aims to reduce certain sources of bias when testing the effectiveness of new treatments; this is accomplished by randomly allocating subjects to two or more groups, treating them differently, and then comparing them with respect to a measured response. One group—the experimental group—has the intervention being assessed, while the other—usually called the control group—has an alternative condition, such as a placebo or no intervention. The groups are followed under conditions of the trial design to see how effective the experimental intervention was. Treatment efficacy is assessed in comparison to the control. There may be more than one treatment group or more than one control group.

Clinical trials are experiments or observations done in clinical research. Such prospective biomedical or behavioral research studies on human participants are designed to answer specific questions about biomedical or behavioral interventions, including new treatments and known interventions that warrant further study and comparison. Clinical trials generate data on safety and efficacy. They are conducted only after they have received health authority/ethics committee approval in the country where approval of the therapy is sought. These authorities are responsible for vetting the risk/benefit ratio of the trial – their approval does not mean that the therapy is 'safe' or effective, only that the trial may be conducted.

The science of epidemiology has matured significantly from the times of Hippocrates, Semmelweis and John Snow. The techniques for gathering and analyzing epidemiological data vary depending on the type of disease being monitored but each study will have overarching similarities.

A cohort study is a particular form of longitudinal study that samples a cohort, performing a cross-section at intervals through time. While a cohort study is a panel study, a panel study is not always a cohort study as individuals in a panel study do not always share a common characteristic.

Case–control study

A case–control 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 with patients who do not have the condition/disease but are otherwise similar. They require fewer resources but provide less evidence for causal inference than a randomized controlled trial. We only get odds ratio from a case–control study, which is an inferior measure of strength of association as compared to relative risk.

Womens Health Initiative long-term U.S. national health study that has focused on strategies for preventing the major causes of death, disability, and frailty in older women, specifically heart disease, cancer, and osteoporotic fractures

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Scientific control subject or observation selected to minimize the effects of variables other than the independent variable of an experiment

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Clinical study design is the formulation of trials and experiments, as well as observational studies in medical, clinical and other types of research involving human beings. The goal of a clinical study is to assess the safety, efficacy, and / or the mechanism of action of an investigational medicinal product or procedure, or new drug or device that is in development, but potentially not yet approved by a health authority. It can also be to investigate a drug, device or procedure that has already been approved but is still in need of further investigation, typically with respect to long-term effects or cost-effectiveness.

Confounding A variable that influences both the dependent variable and independent variable causing a spurious association

In statistics, a confounder is a variable that influences both the dependent variable and independent variable, causing a spurious association. Confounding is a causal concept, and as such, cannot be described in terms of correlations or associations.

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The DASH diet is a dietary pattern promoted by the U.S.-based National Heart, Lung, and Blood Institute to prevent and control hypertension. The DASH diet is rich in fruits, vegetables, whole grains, and low-fat dairy foods; includes meat, fish, poultry, nuts, and beans; and is limited in sugar-sweetened foods and beverages, red meat, and added fats. In addition to its effect on blood pressure, it is designed to be a well-balanced approach to eating for the general public. DASH is recommended by the United States Department of Agriculture (USDA) as one of its ideal eating plans for all Americans.

In epidemiology, Mendelian randomization is a method of using measured variation in genes of known function to examine the causal effect of a modifiable exposure on disease in observational studies. The design was first proposed in 1986 and subsequently described by Gray and Wheatley as a method for obtaining unbiased estimates of the effects of a putative causal variable without conducting a traditional randomised trial. These authors also coined the term Mendelian randomization. The design has a powerful control for reverse causation and confounding, which often impede or mislead epidemiological studies.

A quasi-experiment is an empirical interventional study used to estimate the causal impact of an intervention on target population without random assignment. Quasi-experimental research shares similarities with the traditional experimental design or randomized controlled trial, but it specifically lacks the element of random assignment to treatment or control. Instead, quasi-experimental designs typically allow the researcher to control the assignment to the treatment condition, but using some criterion other than random assignment. In some cases, the researcher may have control over assignment to treatment. Quasi-experiments are subject to concerns regarding internal validity, because the treatment and control groups may not be comparable at baseline. With random assignment, study participants have the same chance of being assigned to the intervention group or the comparison group. As a result, differences between groups on both observed and unobserved characteristics would be due to chance, rather than to a systematic factor related to treatment. Randomization itself does not guarantee that groups will be equivalent at baseline. Any change in characteristics post-intervention is likely attributable to the intervention. With quasi-experimental studies, it may not be possible to convincingly demonstrate a causal link between the treatment condition and observed outcomes. This is particularly true if there are confounding variables that cannot be controlled or accounted for.

Pharmacoepidemiology is the study of the uses and effects of drugs in well-defined populations.

A glossary of terms used in clinical research.

Epidemiology of cancer The study of the extent of cancer spread

The epidemiology of cancer is the study of the factors affecting cancer, as a way to infer possible trends and causes. The study of cancer epidemiology uses epidemiological methods to find the cause of cancer and to identify and develop improved treatments.

Prevention science is the application of a scientific methodology that seeks to prevent or moderate major human dysfunctions before they occur. Regardless of the type of issue on hand, the factors that lead to the problem must be identified and addressed. Prevention research is thus focused primarily on the systematic study of these potential precursors of dysfunction, also known as risk factors; as well as components or circumstances that reduces the probability of problem development in the presence of risk, also known as protective factors. Preventive interventions aim to counteract risk factors and reinforce protective factors in order to disrupt processes or situations that give rise to human or social dysfunction.

References

  1. 1 2 3 "Epidemiology and Public Health". courses.lumenlearning.com. Retrieved 23 March 2018.
  2. "experimental epidemiology". medical-dictionary.thefreedictionary.com. Retrieved 23 March 2018.
  3. Ahrens, Wolfgang; Pigeot, Iris (2007-07-26). Handbook of Epidemiology. Springer. p. 7. ISBN   9783540265771.
  4. Bonita, R.; Beaglehole, R.; Kjellström, Tord. "Basic Epidemiology" . Retrieved 23 March 2018.