Epidemiology is a field of medicine that investigates disease on a population level through the use of statistical tools. Epidemiological research looks for statistical correlations between different phenomena in an attempt to elucidate a relationship between them. While such a study can demonstrate a statistical correlation, it cannot provide insight into a physiological mechanism by which A causes B (causal link).
In order to prove a causal association in science, physiological (biomedical, mechanistic) studies must be performed. In medicine, a causal link between two phenomena is often ambiguous and difficult to identify. A certain condition may be caused by several co-factors operating synergistically, each required for its development, but none causing it on its own.
That is, a risk factor present in a particular person, heavy and prolonged smoking, for instance, might not necessarily cause the disease, lung cancer, in that individual. The difficulty in identifying relevant risk factors–including their roles, relative importance, and interrelationships–makes it challenging for modern medicine to explain the origins of many diseases.
It is quite common, therefore, for medical bodies to make recommendations without a thorough understanding of the mechanism underlying a specific health condition. One such recommendation is the advice to parents to lay babies on their backs to prevent “crib death”, which is based entirely on epidemiological data.
Epidemiological studies come in several varieties.
In an interventional study (trial), subjects are asked by researchers to take specific actions (e.g., take a drug), while in an observational study, researchers only gather information about the subjects.
A prospective study tracks a group of people for a specific period of time and collects relevant data about them.
A retrospective study analyzes existing data. Interventional studies are more expensive to perform than observational studies, but their results are generally of higher quality.
Prospective studies are more expensive and take longer than retrospective studies, but they suffer less from selection and information bias, which makes their results more reliable.
Epidemiological studies cannot predict whether a particular individual will get a certain disease, nor can they prove that a particular factor was, or wasn’t, the cause for that individual’s disease.
Since they only deal with statistical correlations, they cannot refute the results of physiological studies.
The fields of epidemiological and physiological research complement each other.
Each has its own advantages, disadvantages, and uses.
Despite the fact that formal techniques and statistical tools are used in epidemiological research, there are no fixed recipes to follow when designing studies.
Researchers must carefully select the research method, collect complete and reliable data, neutralize any bias, and apply correct analytical methods.
Producing high-quality, meaningful research is no simple matter; some even consider it an art form.”
— Turtles All The Way Down: Vaccine Science and Myth by Anonymous
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Author: brianpeckford
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