Inga Reynisdottir and colleagues from deCODE Genetics, Inc., Reykjavík, Iceland, and the National University Hospital at Hringbraut and the National University Hospital at Fossvogur, also both in Reykjavik, Iceland, conducted a study to examine the genetic component in inflammatory bowel disease in Iceland.
Crohn's disease and ulcerative colitis (collectively inflammatory bowel disease) have both been shown to result from both genetic and environmental factors.
The research group therefore used a population-based sample, representing everyone diagnosed with inflammatory bowel disease (IBD) in Iceland from 1950 to 1996. This sample was studied using a computerized population-wide genealogic database.
This allowed to relationships among patients to be analyzed by calculating the kinship coefficient and the relative risk.
Using this type of analysis, the researchers were able to show that the kinship coefficients for the patients were significantly greater than the mean kinship coefficient for the controls.
The risk ratio for siblings of IBD, ulcerative colitis, and Crohn's disease patients was 5.0, 5.9, and 4.1 respectively, while the cross-risk ratio for siblings of ulcerative colitis patients developing Crohn's disease (or vice versa) was 2.6.
According to the research group, their results indicate that the IBD patients are more closely related than the controls, which strongly supports the involvement of a genetic component in the development of IBD in Icelandic patients.
Going into more detail, the researchers add that they found the increase in risk for relatives of ulcerative colitis probands (the family member through whom a family medically "comes to light") to develop ulcerative colitis, or relatives of Crohn's disease probands to develop Crohn's disease, is greater than the increase in risk for relatives of ulcerative colitis probands to develop Crohn's disease, or relatives of Crohn's disease probands to develop ulcerative colitis.