Exposome-wide association studies: A data-driven approach for searching for exposures associated with phenotype

Abstract

The promise of a unified way to measure the human exposome is the discovery of novel environmental factors associated with and potentially causative of disease. The human exposome has been tentatively defined as the totality of environmental exposures such as dietary nutrients, pharmaceutical drugs, infectious agents, and pollutants encountered from birth to death. Much as human genetics has benefited from high-throughput profiling in the form of genome-wide association studies (GWAS), a data-driven paradigm for the exposome is needed to systematically and reproducibly discover the environmental determinants of disease. In this chapter, we describe methods for associating the exposome with phenotypic state such as disease. Specifically, this chapter will describe hands-on analytic examples and data to search the exposome for correlates with phenotype, called the "environment/ exposome-wide association study" (EWAS). First, we will describe the philosophy behind such a study, including transparency and mitigation of the chances for selection biases. Second, we will describe how to mitigate chances of type 1 error and investigate the possibility of true signals in a sea of possible false positives. We will describe open-source tools for visualization and display of correlated data to enable investigators to efficiently ascertain patterns in phenotypic associations. We end by describing a few success stories of the approach.