Evaluation of risk factors for chronic diseases using case controls
Case control studies compare a group of people with a disease or condition to another group of people without it. The Doll and Hill (1950) study of cigarette smoking and cancer in Britain is a classic example, and is credited with starting our current series of efforts to control tobacco use.
Long term population studies using cohorts
In cohort studies, subjects are categorized on a predetermined basis and followed over time for the development of health conditions. One well-known example is the Framingham Heart Study in which 5200 residents were followed over 35 years. Findings of this study have been used to develop improved cardiovascular disease prevention methods.
Design of clinical trials to evaluate interventions
Clinical trials in humans are conducted to determine whether methods found effective in laboratory conditions can be safely applied to a large population under “normal” conditions to demonstrate its application to the control of disease.