Epidemiological Study Designs

Introduction

When pharmaceutical companies invent new drugs they determine safety and effectiveness by conducting a series of research studies using a limited number of patients. All new treatments can be tested this way. This type of study is called a clinical trial. Clinical trials are an example of one of the epidemiological study designs that you will learn about in this module. You will also be introduced to case control, ecological, cohort, and cross-sectional studies.

Essentials Questions

What are the strengths and limitations of the different epidemiological study designs?
When is it appropriate to use a descriptive study design versus an analytic study design?
How do we control bias in epidemiological studies?

Key Terms

Observational study - a study in which researchers observe events for individuals in the study without altering them.
Experimental study - a study where the participants are purposely manipulated for the purpose of studying the effect of an intervention.
Cohort study - a study in which individuals who have been exposed to a selected health outcome are compared with another group of individuals who have not been exposed.
Case control study - an observational epidemiological study of persons with the disease of interest and a suitable control group of persons without the disease are compared to see if the cases are more or less likely than the controls to have had the disease.
Cross sectional study - a study that involves observation of all of a population, or a representative subset, at one specific point in time.
Ecologic study - a study involving making comparisons between variables from data at the population level.
Bias - systematic error in the collection or interpretation or epidemiological data.
Selection bias - bias in the selection of individuals for a study.
Case - individuals with the disease or outcome being studied.
Control - individuals without the disease or outcome being studied.

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