Quiz 9: Epidemiological Applications


Epidemiology is the science that deals with the study of the distribution of a disease in a population and its determinants. It is helpful in understanding the factors contributing to health and disease, health promotion, disease prevention measures, infectious agent's detection, and characterization. It involves a detailed prospect of disease with reference to a person, place, time, factors, characteristics, behaviors, and contexts that influence health parameters. Epidemiology also focuses on the causes and associated factors that boost disease progression. Epidemiological studies involve detailed study of the selected population for the identification of possible causes of disease and health in the communities. This investigation helps in evaluating interventions that are necessary for maintaining good health. In fourth century Hippocrates firstly examined health and disease in the community based on its geography, climate, seasons, food, and water consumed. In the eighteenth and nineteenth century a drastic change occurs in the Hippocrates conceptual use of quantitative methods began for analysis. During the twentieth century development of antibiotics, vaccination and chemotherapies influenced the further development of epidemiology. In the twentieth century the concentration from single disease epidemiology changed to etiology based on many factors. People started realizing that all diseases are not age specific. With the development of genetics and molecular technique, epidemiologist started understanding the classification of persons in terms of exposures and inherent susceptibility to disease.

Epidemiology focuses on health state distribution and events. Epidemiologists often use geographic information system to identify the disease patterns. Rates and proportions are important for epidemiological studies. In proportion, ratio denominator includes the numerator. Proportion can vary between 0 to 1. For getting the percentage, these proportions are multiplied by 100. The rate is defined as the measure of the health event frequency in different populations at certain periods. In rate ratio, the denominator is a function of population size and dimension of time while the numerator represents a number of events. The rate may be greater than 1. Risk represents the probability of an event occurrence within a specified period. A risk population is the population, in which there is some probability of disease occurrence. There are some exceptions for the risk factors also. Epidemiology explains that the disease occurrence is a complex process among the causative agents, persons with susceptibility, and environmental factors. Agent, host and environment elements together are called the epidemiological triangle. A change in any one of the factors in the triangle may affect the disease occurrence process. The ecological model treats the multiple health determinants as they are correlated with each other and act parallel.

Epidemiology can be defined as a study of determination of states of health, events in the population of humans, its distribution as well as the application of such studies in control as well as the prevention of any health related consequences. Information on epidemiology plays a very essential role in completing the objectives of public health that is aimed for promoting mental, physical as well as well-being inside the population. The steps in the epidemiological process are as follows: 1. Data sources- It is the first step in the epidemiological process to know how the data will be obtained. Birth and mortality statistics are calculated from vital records. It gives health related information, hence vital in many countries. Census data, birth certificates, death certificates, and surveillance data come under this category. 2. Rate adjustment- Rates are an essential factor for epidemiological studies. Age adjustment is done by direct or indirect methods. A standard population is considered as an external population that serves as a reference. 3. Comparison groups- The exposed group is compared with the unexposed group to decide, whether the disease rate is the result of suspected risk factors. This comparison is important for observational studies to control for confounding variables or factors.

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