Genetics and environmental factors are implicated in the etiology of inflammatory bowel disease (IBD). We studied environmental factors in a population-based Swedish-Danish twin cohort using the co-twin control method. SUBJECTS AND
Methods
A questionnaire was sent to 317 twin pairs regarding markers of exposures in the following areas: infections/colonization and diet as well as smoking, appendectomy, and oral contraceptives. Odds ratios (OR) were calculated by conditional logistic regression. When confounding appeared plausible, multivariate conditional logistic regression was added. The questions were also divided into topic groups, and adjustment was made for multiple testing within each of the groups.
Results
The response rate to the questionnaire was 83%. In consideration of the study design, only discordant pairs were included (Crohn's disease [CD], n = 102; ulcerative colitis [UC], n = 125). Recurrent gastrointestinal infections were associated with both UC (OR, 8.0; 95% confidence interval [CI], 1.0-64) and CD (OR, 5.5; 95% CI, 1.2-25). Hospitalization for gastrointestinal infections was associated with CD (OR, 12; 95% CI, 1.6-92). Smoking was inversely associated with UC (OR, 0.4; 95% CI, 0.2-0.9) and associated with CD (OR, 2.9; 95% CI, 1.2-7.1).
Conclusions
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.
PMID 17012962 17012962 DOI 10.1097/01.mib.0000228998.29466.ac 10.1097/01.mib.0000228998.29466.ac
Cite this article
Halfvarson, J., Jess, T., Magnuson, A., Montgomery, S., Orholm, M., Tysk, C., Binder, V., & Järnerot, G. (2006). Environmental factors in inflammatory bowel disease: a co-twin control study of a Swedish-Danish twin population. Inflammatory bowel diseases, 12(10), 925-933. https://doi.org/10.1097/01.mib.0000228998.29466.ac
Halfvarson J, Jess T, Magnuson A, Montgomery S, Orholm M, Tysk C, et al. Environmental factors in inflammatory bowel disease: a co-twin control study of a Swedish-Danish twin population. Inflamm Bowel Dis. 2006;12(10):925-933. doi:10.1097/01.mib.0000228998.29466.ac
Halfvarson, Jonas, et al. "Environmental factors in inflammatory bowel disease: a co-twin control study of a Swedish-Danish twin population." Inflammatory bowel diseases, vol. 12, no. 10, 2006, pp. 925-933.
Previous epidemiological studies suggesting an association between oral contraceptive use and ulcerative colitis incidence have been weak and conflicting. To measure a possible association, 46 incident cases of ulcerative colitis patients, women aged 18-50 years, were compared with peer-nominated age-matched and sex-matched controls. There were no differences between case and control patients in demographic characteristics. There was no association between oral contraceptive use and ulcerative colitis (current odds ratio 0.70, 95% confidence interval 0.27-1.83; odds ratio 1.14, confidence interval 0.41-3.15; odds ratio 0.86, confidence interval 0.40-1.85). Stratifying by disease location (pancolitis or left-sided disease) also failed to identify an association. Controlling for possible confounding effects of cigarette smoking did not alter the lack of association between oral contraceptive use and ulcerative colitis. Similarly, testing for interaction failed to demonstrate any effect modification. Analyzing for duration of current oral contraceptive use or time interval since last use failed to demonstrate a "dose-response" effect. The study was of sufficient size to detect statistical significance for oral contraceptive use for odds ratios of 2.8 and higher. In this matched case-control study of incident cases and community controls, there was no association between oral contraceptive use and ulcerative colitis incidence. To date, there is no evidence suggesting that women predisposed to the development of ulcerative colitis should be advised to avoid oral contraceptive use.
Previous epidemiologic studies have suggested a weak association between oral contraceptive use and Crohn's disease, specifically Crohn's colitis. To measure a possible etiologic association, 51 women with Crohn's disease who were 18-50 yr old were studied and compared with peer-nominated ageand sex-matched controls. There were no differences between cases and controls with respect to race, religion, marital status, and number of pregnancies. There was no association between oral contraceptive use and Crohn's disease incidence [current odds ratio (OR) 0.73, 95% confidence interval (CI) 0.34-1.59; OR 1.80, CI 0.61-5.29; OR 1.00, CI 0.46-2.16]. Stratifying by disease location also failed to identify an association. Cigarette smoking was significantly associated with Crohn's disease incidence. Controlling for possible confounding effects of cigarette smoking did not alter the lack of association between oral contraceptive use and Crohn's disease. Similarly, testing for interaction failed to demonstrate any effect modification. Analyzing for duration of current oral contraceptive use or time interval since last use failed to demonstrate a "dose-response" effect. The study was of sufficient size to detect statistical significance for oral contraceptive use for odds ratios of greater than or equal to 2.76. From this community-based matched case-control study, there was no association between oral contraceptive use and Crohn's disease, and women need not be advised to discontinue oral contraceptive use when a diagnosis of Crohn's disease is made.
General OB/GYNInflammatory Bowel DiseaseAutoimmune Disease RiskTwin Studies
Twin studies provide insight into the complex interaction between genetic and environmental factors in the development of inflammatory bowel disease (IBD). We assessed associations between childhood environmental factors and development of Crohn's disease (CD) and ulcerative colitis (UC) in twins. Questionnaires on clinical demographics and exposure to environmental factors were sent to twins with IBD, their healthy co-twins, and their doctors. Kappa statistics were used to examine agreement between twin pairs and odds ratios were calculated by conditional logistic regression. In all, 250 IBD twin pairs (122 CD; 125 UC; 3 CD/UC; 28 concordant pairs) were analyzed. Concordant monozygotic twins with CD showed good agreement for disease location (κ 0.88; 95% confidence interval [CI]: 0.45-1.00), disease behavior (κ 1.00; 95% CI: 0.43-1.00), and moderate agreement for age at diagnosis and need for medical and surgical therapy. Concordant monozygotic twins with UC showed good agreement for disease extent (κ 0.60; CI 0.13-1.00) and use of thiopurines (κ 0.73; CI 0.10-1.00). In discordant twins, symptomatic childhood mumps infection (odds ratio [OR], 3.8; 95% CI, 1.2-11.3) and oral contraceptives (OR, 4.0; 1.1-14.2) were associated with CD. Smoking was associated with CD (OR, 4.3; 95% CI, 1.9-9.8) but inversely associated with UC (OR, 0.3; 95% CI, 0.1-0.9). Both CD and UC twins had suffered more "gastroenteritis" and spent more time with animals than their co-twins. Disease phenotype in CD and disease extent in UC appeared to be genetically influenced. Smoking is a risk factor for CD but is protective for UC. Early exposure to "infections" during childhood may be associated with the development of IBD.
General OB/GYNInflammatory Bowel DiseasePopulation-Based Studies
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