Commentary: Migrant study designs for epigenetic studies of disease risk

Comparisons of migrant, native and host populations are particularly useful in elucidating the balance between genetic and environmental influences on disease risk. In this issue, Campanella and colleagues 1 have conducted a novel study of epigenetics in Italian migrants and non-migrants from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Italy. Differences in DNA methylation were identified at several CpG sites when comparing migrant and host populations, including after adjustment for available dietary and lifestyle factors. They hypothesized that patterns they observed fit with an adaptive mechanism to counter the mismatch between early life exposures and later life environment experienced in the migrant population. The role of epigenetics and its interaction with the genome to mediate the changing health outcomes observed in many migrant groups is clearly important. However, migrant studies are complex. The effects of changing environments on health outcomes vary not only according to ethnicity and regions of origin and destination, but also according to who is migrating, why and when they migrate and what health outcome is being measured and over what period. We discuss a small selection of historic migrant studies in order to illustrate their utility and interpretation, alongside aspects of the new epigenetic study by