A recent review suggests that migration and race influence the risk of developing inflammatory bowel disease. In particular, South Asian migrants have a consistently higher incidence of ulcerative colitis and a lower incidence of Crohn’s disease, researchers have found.

The review titled, “Epidemiology of inflammatory bowel disease in racial and ethnic migrant groups,” was published in the World Journal of Gastroenterology.

Ulcerative colitis (UC) and Crohn’s disease (CD) comprise a chronic inflammatory condition known as inflammatory bowel disease (IBD). While the cause is unknown, it is thought to emerge as an exaggerated immune response to various stimulations by the gut microbiome. IBD tends to develop in people who are genetically susceptible.

Some studies have reported that migrants who move away from countries with low incidence to countries with high incidence of theses diseases tend to change and exhibit the disease prevalence of the adopted country. This is interesting as it implies there may be an environmental trigger for the diseases.

So, European researchers sought to summarize the current literature and define patterns of disease in migrant and racial groups. Thirty-three studies on incidence, prevalence and disease phenotype of migrants and races, compared with indigenous groups, were eligible for inclusion in the review.

“Migrants” is a term that refers to people who move to a new country as a first generation, or second generation when born there. The term “race” classifies people biologically according to physical characteristics.

Sifting through the Individual studies, researchers found there were significant variations in the incidence, prevalence and disease type between migrants or race and indigenous groups.

A pooled analysis conducted using incidence studies on South Asians showed that, compared to the Caucasian population, South Asians had a lower incidence of CD with a rate ratio of 0.78, and a higher incidence of UC with a rate ratio of 1.39.

Across five countries, South Asians showed consistently higher incidence and more extensive UC than the country’s indigenous population. Interestingly, a similar pattern was observed for Hispanics in the United States.

The results from this study suggest that migration and race influence the risk of developing IBD, which may be due to “different inherent responses upon exposure to an environmental trigger in the adopted country,” the researchers concluded.

Researchers are becoming increasingly interested in the role of environmental factors on microbial colonization. The study authors added that “studying these early life perturbations in a genetically predisposed population, such as second generation migrants, bought up in a ‘western’ environment, for example SA (South Asians], may help to decipher the impact of genetic and environmental factors.”