IE - Epidemiology Defined Lesson

Epidemiology Defined

Before reading about Epidemiology, watch this brief video: What is Epidemiology?

 

Epidemiology is...

...the study of the patterns, causes, and effects of health and disease in defined populations. It is the cornerstone of public health, and informs policy decisions and evidence-based medicine by identifying risk factors for disease and targets for risk factors. Epidemiologists help with study design, collection and statistical analysis of data, and interpretation and dissemination of data. Major areas of epidemiological study include disease etiology, outbreak investigation, disease surveillance and screening, monitoring, and comparisons of treatment effects such as in clinical trials. Epidemiologists rely on other scientific disciplines like biology to better understand disease processes, biostatistics to make efficient use of the data and draw appropriate conclusions, and social sciences to better understand risk factors using exposure assessment.

For a long time the predominant interest in epidemiology was the area of infectious diseases. The occurrence of highly contagious infectious diseases varied in obvious ways, and often increased dramatically from time to time. It was found that individuals who had been in contact with sick people often became ill themselves and that those who recovered seldom got sick again. Such epidemiologic observations became the basis of theories about infectiousness and immunity and suggested effective means to prevent diseases, even before microorganisms and antibodies were discovered.
Epidemiologic studies contributed decisively to understanding the role of cigarette smoking in the occurrence of lung cancer. Other studies have shown that there is an association between exposure to some types of ionizing radiation and certain forms of cancer. Many epidemiologic studies have demonstrated the connection between exposure to certain chemical substances and some kinds of malignant tumors.

These examples of fields of application suggest a close connection between epidemiology and preventive medicine. In general, prevention interventions maybe evaluated by comparing disease rates among those receiving the preventive program with rates among those who do not. In recent years the value of information about disease distribution for planning the delivery of health care has become more apparent. In several studies disease occurrence has been related to healthcare need, demand, and supply. There is also an increasing interest in studying the effectiveness of the healthcare system and/or of different treatments.

The common basis for these different applications of epidemiology is the study of disease occurrence and its relation to various characteristics of individuals or their environment. Descriptive and Analytical Epidemiology are two methods that are used to study disease. Descriptive epidemiology deals with the distribution of health outcomes and analytical epidemiology deals with the causes of health outcomes. The next section deals with descriptive epidemiology, you will learn about analytical epidemiology in a later module.

Descriptive Epidemiology

Descriptive Epidemiology is the aspect of epidemiology concerned with organizing and summarizing data regarding the persons affected, time, and place. Epidemiologists utilize person, place, and time information to describe how the disease is distributed. The description of who the sick people are, where they are sick, and when they became sick is the descriptive epidemiology of the disease. Person level descriptors include age, gender, race/ethnicity, occupation, and education. Place descriptors include occupation, residence, geographical site, presence at specific events, and anatomical site. Time descriptors include year, season, day, date of onset, and duration. Each disease has its own descriptive epidemiology.

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