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P328. Revaluation of risk factors for inflammatory bowel diseases according to the “hygiene hypothesis”: A South-Italian, case–control, multi-centre prospective study

A. Rispo1, M. Diaferia1, F. Morace2, C. Meucci3, A. Panarese4, A. Cuomo5, A. Testa1, M. Romano6, M. Rea1, F. Sasso1, C. D'Onofrio1, F. Castiglione1

1Gastroenterology, University “Federico II” of Naples, Naples, Italy; 2Gastroenterology, San Gennaro Hospital, Naples, Italy; 3Gastroenterology, Maresca Hospital, Torre del Greco, Italy; 4Gastroenterology, Hospital “Santa Maria delle Grazie”, Pozzuoli, Italy; 5Gastroenterology, Hospital “Umberto I”, Nocera Inferiore, Italy; 6Gastroenterology, Second University of Naples, Naples, Italy

Introduction/Objectives: Ulcerative colitis (UC) and Crohn's disease (CD) are two inflammatory bowel diseases (IBD) of unknown aetiology. The “hygiene hypothesis” (HH) is thought to be a significant contributor to the increased incidence of auto-immune diseases in the last decades. Regarding IBD, the HH could be supported by the evidence of a deficient immunological response to infections, probably secondary to the lack of previous antigenic exposure.

Aim: To revaluate risk factors for IBD according to HH.

Methods: We prospectively performed a questionnaire-based, case–control, multi-centre study focused on the principal risk factors for development of IBD according to HH. We investigated the main surrogated markers of HH (childhood and helmintic infections; antibiotics in childhood; breastfeeding; family size/sibship; urban upbringing; personal and domestic hygiene) in UC and CD patients, in comparison with a control group of functional dyspeptic subjects. In addition, the traditional risk factors for IBD (familial aggregation, smoke, appendectomy) were also recorded. Statistics were performed by using Pearson's chi-square and relative risk values. The analysis was two-tailed; p < 0.05 was considered significant.

Results: The study population included 330 UC, 268 CD and 354 controls. None of the surrogated risk factors of HH was significant in IBD population. On the contrary, the traditional risk factors confirmed their statistical significance in IBD population. Familial aggregation was the main risk factor (RR 4.8 for UC; RR 5.1 for CD). Furthermore, both smoking habit and appendectomy confirmed their opposite risk profile in IBD (smoking habit: RR 0.5 for UC; RR 1.8 for CD; appendectomy: RR 0.22 for UC; RR 1.5 for CD).

Conclusion: Even if HH is a suggestive interpretative explanation for the increasing calendar trend of IBD incidence, its actuarial role in our population appears to be not significant. Familial aggregation, smoking habit and appendectomy still remain the main risk factors associated with IBD.