The promises and challenges of epigenetic epidemiology.

The union between epidemiology and epigenetics creates a new science that combines the strengths of both fields: the appropriate study design with adequate sample size to identify disease biomarkers and to uncover mechanistic pathways for environmental exposure and disease associations while controlling for confounding variables. Realization of the promises of epigenetic epidemiology requires overcoming some challenges in the design, conduct, and interpretation of epigenetic studies in human populations. These challenges include the choice of the appropriate tissue, confounding, misclassification, and effect modification. In particular, the tissue-specificity of epigenetic marks restricts epidemiologic studies of adequate size to easily accessible tissues.