12.0: Introduction
Did you ever wonder where clinical guidelines originate? For example, screening for lung cancer with computed tomography is recommended for adults 50–80 years of age who have a 20-pack-a-year smoking history. On what evidence is this recommendation based? Recommendations like this one are the result of epidemiological study. This chapter will introduce basic concepts of epidemiology, how it has evolved, and how it is used today, focusing on the application of epidemiology to public health practice.