To test the theories put forward within descriptive epidemiology, researchers are turning to analytic epidemiology, which includes observational and experimental studies. Carneiro and Howard (2011) affirm that observational study does not involve interventions and experiments. In an observational study, events are given a natural course, and changes in one feature are compared with others. These studies include case-control and cohort studies.
A case-control study may be performed to identify an association between any risk factor and clinical outcome. Such a study compares the proportion of participants who experienced adverse effects in two groups, one of which developed and the other did not have the clinical outcome under study. Also, as part of such a study, individuals with a particular disease can be compared with those who do not have the disease (CDC, 2012). The relationship between the trait and the disease is studied by comparing patients and non-patients by the frequency of occurrence of the trait among them or, if the traits are quantitative, by the level of the trait in each group. For example, such a study could analyze the relationship between tuberculosis and smoking among residents of a rural district who have tuberculosis and who are healthy.
A cohort study involves studying factors that may cause the development of a particular disease. For example, among TB patients in rural areas, the influence of lifestyle on the risk of developing TB can be studied. Such characteristics as gender, age, zip code, and ethnicity will be considered, as well as smoking, alcohol consumption, sports activities, and family history of TB.
An experimental study is a study in which a population is selected for a planned trial of an intervention, and the effects of treatment in the experimental group are studied by comparing the outcome with another intervention in the control group. Its main difference from various observational studies is that the authors of such studies are not passive observers of the phenomena of interest to them. Still, they influence the objects under study to assess subsequent changes. For example, an experiment on how a protein diet affects the course of tuberculosis among residents of a rural district can be conducted.
Carneiro, I. & Howard, N. (2011). Introduction to epidemiology (2nd ed.). Open University Press.
Centers for Disease Control and Prevention (CDC). (2012). Lesson 1: Introduction to epidemiology, Section 7: Analytic epidemiology. Principles of epidemiology in public health practice (3rd ed.), pp. 1-31. U.S. Department of Health and Human Services, Office of Workforce and Career Development. Web.