Epidemiology

The word epidemiology comes from the Greek words epi, meaning on or upon, demos, meaning people, and logos, meaning the study of. In other words, the word epidemiology has its roots in the study of what befalls a population. Many definitions have been proposed, but the following definition captures the underlying principles and public health spirit of epidemiology:
Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems (1). To continue reading about the definition of epidemiology visit the book developed by the Centers for Disease Control and Prevention (CDC) available here.

The CDC breaks this definition down into the important principles of epidemiology, check it here
The most common types of epidemiological studies are case studies, cross sectional studies and cohort studies:

• Case studies describe characteristics of a group of people who have the same disease or the same exposure. Its major aim is to understand the demographics, presentation and prognostics.
• Cross sectional studies take a selected population, that is representative of the whole population and measure health information at a certain point in time. They are also known as prevalence studies when they measure the number of people with a disease at a particular point in time.
• Cohort studies follow a group of people during a certain period of time in order to collect information about the risk factors. Its main purpose is to compare outcomes between the people who were exposed to a certain risk factor (example: disease), and those who were not.

• Let's Learn Public Health prepared a video, where an overview of the most common types of epidemiological studies, their advantages and disadvantages is given.  It also looks at systematic reviews and meta-analysis. Watch it below:

   

References:

1. Introduction to Epidemiology. Lesson 1 in: Centers for Disease Control and Prevention. Principles of Epidemiology in Public Health Practice, An Introduction to Applied Epidemiology and Biostatistics. https://www.cdc.gov/OPHSS/CSELS/DSEPD/SS1978/Lesson1/Section1.html (accessed April 2021)