About Epidemiology

Epidemiology is, literally, the study of epidemics--what causes them, where they come from and how often they occur--but inherently includes the study and prevention of illnesses and disease. Research in this field incorporates an interdisciplinary approach that relies on data, information and methods used in a variety of different fields.

Instructions

Function

1. The observation of how and when diseases arise became necessary as populations grew. Epidemiology is the primary means by which health problems are contained, prevented and controlled within populations. Its methodologies form the basis of public health research.

   Through the use of data collection and analysis, statistical models are constructed from which hypotheses are tested. Drawing from a number of related disciplines--social science, biology, medicine, mathematics, statistics, psychology, social policy and anthropology--epidemiology is able to observe, define and predict patterns of disease and illness within target populations. Specialists in this field can be found in a variety of settings depending on their areas of expertise.

Identification

1. The "epidemiologic triad" is the fundamental model used within the field to examine causal relationships between a host, an agent and an environment, where the host is the population observed, the agent is the illness or disease being tracked and the environment is the area in which the agent is active.

   Specific criteria are employed to asses the validity of observed causal relationships within the epidemiologic triad. Cause-effect relationships are determined by
   · consistency in findings--experimental versus observation
   · specificity of conditions--a particular place, a particular population and a specific set of health problems
   · reasonable cause--an identifiable way by which illness can spread
   · probability--based on the presence of similar factors

History

1. Hippocrates is recognized as the father of epidemiology, having published the first study of environmental influences on human health in the 3rd century, B.C.E. Titled "On Airs, Waters, and Places," Hippocrates records cause-effect occurrences of illness and disease within a population using observational methods.

   As of the 17th century, quantitative methods were incorporated into the study of public health. John Graunt was the first to apply the principle of "social arithmetic" in the field, marking an official beginning to the field of modern epidemiology. His book, "Observations on the Bills of Mortality" made use of church christening records, death certificates and burial records and identified causes of death to compile patterns of illness and life expectancy rates.

   The standard epidemiological nomenclature and classification system in use today was first compiled by William Farr in the mid-19th century. Using health data statistics from military records and census data collections gathered from his involvement in the first modern census (conducted in Great Britain), Farr formulated a general law of epidemics and invented the first standardized mortality rate table.

Types

1. There are two basic types of epidemiology--descriptive and analytic. The descriptive type deals with specific population groups, whereas the analytic type focuses on health risk factors and preventive measures.

   When working with specific population groups, researchers track health factors by collecting and analyzing how a particular health problem develops, what its symptoms are, its frequency of occurrence and relative mortality rates. Analytic measures are then applied by comparing people within the population group, or target group, who experience illness with the ones who don't to determine how an illness takes root.

   A third approach, which is a variation on both the descriptive and analytic types, is the clinical, or experimental, type. This is a laboratory-based approach that incorporates clinical trials done on volunteers, groups or animals. This research is typically carried out in hospitals and laboratories for the purpose of finding cures and treatments for known diseases.

Considerations

1. 

   With the growth of vast populations of people across many continents, identifying causal factors leading to illness and disease within target groups has become a difficult undertaking. The accuracy and quality of research findings are only as good as the methods used. The cause-effect model of study used uncovers risk factors and probable points of origin; however, final conclusions can only be based on what is inferred from the data.

   Diseases shown to have multiple risk factors are more difficult to track and assess within a target population, especially if no cause for the disease is known. Seemingly insignificant risk factors that show a low incidence of occurrence may play a larger part in the cause-effect process than what can be observed from the data. As modern day illnesses and diseases become more contagious and resistant to cures, the methods of epidemiology and its use within the public sectors will need to accommodate a more global approach in its work.

Resources

• Epidemiology at a Glance
• Epidemiology--Research & Statistics Resources