Genetics and environmental factors are implicated in the etiology of inflammatory bowel disease (IBD).
Dr Jonas Halfvarson and colleagues studied environmental factors in a population-based Swedish-Danish twin cohort using the co-twin control method.
The investigative team sent a questionnaire to 317 twin pairs regarding markers of exposures in several areas.
The team included questions on infections or colonization and diet as well as smoking, appendectomy, and oral contraceptives.
| Some of these effects might be mediated by long-term changes in gut flora|
|Inflammatory Bowel Diseases|
Odds ratios were calculated by conditional logistic regression.
When confounding appeared plausible, multivariate conditional logistic regression was added.
The investigators divided the questions into topic groups, and adjustment was made for multiple testing within each of the groups.
The response rate to the questionnaire was 83%.
In consideration of the study design, the team only included discordant pairs.
The investigators included 102 pairs with Crohn's disease, and 125 with ulcerative colitis.
The team found that recurrent gastrointestinal infections were associated with both ulcerative colitis, and Crohn's disease.
Hospitalization for gastrointestinal infections was associated with Crohn's disease.
The investigators observed that smoking was inversely associated with ulcerative colitis, and associated with Crohn's disease.
Dr Halfvarson's team concludes, “The observed associations indicate that markers of possible infectious events may influence the risk of IBD.”
“Some of these effects might be mediated by long-term changes in gut flora or alterations in reactivity to the flora.”
“The influence of smoking in IBD was confirmed.”