Epidemiology: theory, study design, and planning for education.

Many health professionals have received formal training in epidemiology; however, much of it has been limited to introductory courses at the undergraduate level. Further, continuing education for health professionals has focused historically on substantive rather than methodologic issues in epidemiology. A methodologic focus is recommended to improve continuing education for the health of the public. It is crucial to equip educators and health professionals with the necessary tools or resources to understand study design, conduct research, analyze and interpret data, and critically evaluate published research. Thus, in this article, a general overview of epidemiologic study design and some of the most common methodologic issues are presented. Issues such as confounding, effect modification, measurement error, and power and sample size are highlighted. A broader recognition of these issues by educators and health professionals may ultimately help to improve public health by facilitating effective educational interventions, proper study design, analysis, interpretation, and application of epidemiologic research.