EPIDEMIOLOGICAL METHOD: STAGES AND CHARACTERISTICS, APPLICATION, BRANCHES - MEDICINE - 2025

The epidemiological method can be considered as a scientific method that uses logical reasoning to study the characteristics of diseases and other factors that cause damage to health, all with the purpose of modifying them and positively influencing the health of the population.

Epidemiology is a scientific discipline that studies the frequency and distribution of health-related phenomena and their determinants in specific population groups, using the results of these studies for the control and prevention of health problems.

The epidemiological method is based on the approach to the study based on the scientific method, so it can be said that it is a particular application of the scientific method.

In this case, based on the identification of a problem (disease or health phenomenon) and the review of existing knowledge, a hypothesis is formulated and objectives are set. Subsequently, the data are collected according to a previously developed research design.

Then, once the data has been analyzed and interpreted, conclusions are drawn that will allow modifying or adding new knowledge to existing ones. With this, the proposed objectives may or may not be achieved.

The word epidemiology derives from the Greek "epi" (about), "demos" (people) and "logos" (study or treatise), so it could be translated as "the study of the people."

Stages of the epidemiological method

The epidemiological method makes use of the scientific method and applies it to the health problems of a human population. For this reason it is used based on a series of stages that can be listed as follows:

- Observation of the phenomenon

- Data collection

- Data processing

- Identification and interpretation of the patterns of occurrence

- Hypothesis formulation

- Verification of the hypothesis or hypotheses

- Conclusions and applications.

Descriptive epidemiology, as a branch of epidemiology, deals with the observation and description of the phenomenon that affects the health of a population. It defines the time, place, person, quantifies the distribution of the phenomenon through incidence, prevalence and mortality rates.

In other words, descriptive epidemiology deals with the first four stages described: observation of the phenomenon, data collection, data processing and identification and interpretation of the patterns of occurrence (who, where and when? Person, place and weather).

- Characteristics of each stage

Observation of the phenomenon

For this, an updated information system is needed in which data can be obtained on the distribution of the disease under study in a given population, in a given geographic area and in a defined period of time.

Thus, the epidemiological phenomenon is characterized with the variables of person, time and place. Direct or bibliographic observation is made.

Data collection

They may refer to a causal agent or the one suspected to be the cause of the disease under study. In the cases of infectious agents, the type of agent, the quantity, the speed of reproduction and diffusion, the transformation capacity, among other related aspects, are studied.

In the case of potentially toxic substances, the physicochemical characteristics, production, distribution, etc. are studied.

In the case of risk factors related to habits capable of causing the appearance of a disease, these must be described and the data relating to the case must be collected.

Likewise, mortality and morbidity data are recorded with the patterns of occurrence and prevalence referring to the populations or exposed individuals.

Data processing

The data is tabulated, the required calculations are made and the ordered information is presented for analysis.

Identification and interpretation of the patterns of occurrence

The pattern of occurrence is the characteristic profile in which a disease commonly occurs, adopting particular traits for the different components of the population. The identification of these patterns is one of the core problems of epidemiology.

This is what makes it possible to explain why, when faced with the same risk factors or when exposed to the same agents, some people get sick and others do not. Therefore, factors related to people, place, temporal fluctuations and agents are studied.

Hypothesis formulation

Once the phenomenon under study has been characterized, an informed opinion or hypothesis is raised about the causes or motives for which said phenomenon or event has occurred. Here we enter the analysis. The hypothesis cannot be arbitrary, nor can it contradict solidly established facts.

The hypothesis must be consistent with the scientific knowledge available to date and cannot encompass processes that cannot be demonstrated by the research undertaken.

Verification of the hypothesis (s)

The verification of the proposed hypothesis implies the analytical phase itself, making use of the statistical analysis that allows verifying the reliability of the proposed associations.

Conclusions

Once the hypothesis has been verified, results can be obtained that allow the association of one or more causal or risk factors with the disease under study. This makes it possible to highlight the importance of these factors and propose the pertinent corrective and preventive measures.

Application of the epidemiological method

The application of the epidemiological method allows the identification of some causal or risk factors that affect the health of a particular population, in a geographic environment and in a particular period.

The identification of these phenomena makes it possible to apply specific corrective measures to protect the population at risk, thus preventing the disease, if necessary, taking health education measures and improving epidemiological surveillance services.

Branches of epidemiology

Analytical Epidemiology

Analytical epidemiology, which is another branch of epidemiology, establishes hypotheses and tests them by observation or experimentation.

This branch of epidemiology tries to establish, given all the factors to which the individuals and population groups under study are exposed, which ones are related to health effects.

In other words, it studies the absolute or relative risk factors establishing the probability of getting sick. It studies the determinants of diseases or the reasons why a certain disease has a high or low relative frequency in specific groups.

Experimental epidemiology

Experimental epidemiology, using population groups divided into groups subject or not to certain risk factors, studying how these phenomena affect and how they are related to the causes or determinants of a disease in human populations. So, draw your conclusions.

Ecoepidemiology

Another branch of epidemiology is ecoepidemiology, which studies the interaction of environmental factors with people and populations in their environment, and how these factors influence people's health or the evolution of a particular disease.

References

1. Alberto C Palladino. (2011) Introduction to Epidemiology. National University of the Northeast Primary Health Care, Faculty of Medicine. Epidemiology and Informatics.
2. Bombardier, C. (1988). Research challenges: overview of epidemiological study designs. The Journal of rheumatology. Supplement, 17, 5-8.
3. Elena Ruth Beber (2012) Epidemiological Method University of San Carlos de Guatemala. Faculty of Medical Sciences. Public Health Area. Compiled and reproduced for educational purposes.
4. Miguel Ángel Royo Bordonada, Javier Damián Moreno, (2009) "Epidemiological method". National School of Health (ENS) Carlos III Health Institute - Ministry of Science and Innovation. Madrid: ENS - Carlos III Health Institute
5. Stephenson, JM, & Babiker, A. (2000). Overview of study design in clinical epidemiology. Sexually transmitted infections, 76 (4), 244-247.
6. Thiese, MS (2014). Observational and interventional study design types; an overview. Biochemia medica: Biochemia medica, 24 (2), 199-210.