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Motivation: A steadily increasing number of experiments with microarrays stimulate the further development of the statistical methods of the analysis of gene expression data. One of the central problems in this area is detecting differential gene expression under two or more conditions. Unfortunately, up to now it has not been studied how the correlations between related individuals, such as twins influence the estimates of differential gene expression., Results: In this paper, we discuss this problem and propose a new method that is robust with respect to correlations of gene expression data for twins.

Abstract: Introduction: Environmental factors may play an important role in the pathogenesis of IBD. The history of patients of the German IBD twin study was analyzed by questionnaires and interviews. Methods: Randomly selected German monozygotic (MZ) and dizygotic (DZ) twins with at least one sibling suffering from IBD (n=512) were characterized in detail including demography, medical history and concomitant medications. Controls comprised of non-twin IBD patients (n=392) and healthy subjects (n=207). Results: The most significant variables that were associated with Crohn''s disease (CD) or ulcerative colitis (UC) included living abroad before time of diagnosis (OR, 4.32; 95% CI, 1.57–13.69), high frequency of antibiotic use (MZ CD OR, 5.03; 95% CI 1.61–17.74, DZ CD OR, 7.66; 95% CI, 3.63–16.82, MZ UC OR, 3.82; 95% CI, 1.45–10.56, DZ UC OR, 3.08; CI, 1.63–5.92), high consumption of processed meat including sausage (MZ CD OR, 7.9; 95% CI, 2.15–38.12, DZ CD OR, 10.75; 95% CI, 4.82–25.55, MZ UC OR, 5.69; 95% CI, 1.89–19.48, DZ UC OR, 18.11; 95% CI, 7.34–50.85), and recall of bacterial gastrointestinal infections (MZ CD OR, 15.9; 95% CI, 4.33–77.14, DZ CD OR, 17.21; 95% CI, 4.47–112.5, MZ UC OR, 5.87; 95% CI, 1.61–28.0, DZ UC OR, 11.34; 95% CI, 4.81–29.67). Conclusions: This study reinforced the association of life style events, in particular a specific dietary and infections history, with IBD. Alteration of gut flora or alterations of the mucosal immune system in reactivity to the flora could be an important factor to explain the relationship between life-style and disease. [Copyright &y& Elsevier]