Study designs in genomic epidemiology

The choice of an appropriate study design is a critical first step in any genomic epidemiology research, especially considering the current unprecedented capacity of generating massive information derived from genomics and other "-omics” disciplines. In this chapter, we will review the main types of study designs used to discover novel genes or gene variants related to human diseases, as well as to assess their quantitative impact on disease risk. Several study designs are commonly used in the field of epidemiology (for example, cohort, classical case-control, and case-cohort studies). In contrast, other study designs based on the observation of resemblance among relatives come primarily from the field of human genetics, such as family aggregation, adoption, and monozygotic-dizygotic twin studies. Finally, the massive incorporation of genetic markers and next-generation sequencing data has been used in linkage studies of nuclear or multigenerational families, genomic studies of population isolates, and genome-wide association studies.