How to Do Genetic and Molecular Epidemiologic Research

Epidemiology is an established field that studies the distribution of disease in populations, and evaluates the effects of disease determinants in attenuating disease presentation and natural history. Compared to traditional epidemiology, genetic and molecular epidemiology are relatively young fields that have evolved with recent advances in genetics and molecular biology, and represent the union of several disciplines including laboratory science, biostatistics, and epidemiology. Genetic epidemiology focuses on the study of genetic variants, and their role in disease in the context of environmental factors. Molecular epidemiology studies molecular processes, and how variations in biochemical and cellular processes can impact disease etiology and presentation. As both fields can study the contribution of genetic and environmental risk factors to the development and distribution of disease across families and populations, there is overlap between the two. Importantly, epidemiologic methods can be extremely useful in translating laboratory observations into a better understanding of disease pathophysiology. In this chapter, a brief summary of the fields will be provided, followed by an overview of study designs related to these fields to provide a resource for those wishing to learn more about them when applied to gastrointestinal disease.