Environmental factors and risk of pediatric onset inflammatory bowel disease

Background. Pediatric inflammatory bowel disease (IBD) is a chronic illness that affects as many as 100,000 children and adolescents in the United States. IBD includes Crohn's disease (CD), characterized by inflammatory processes occurring anywhere in the luminal gastrointestinal tract, and ulcerative colitis (UC), where the colon alone is affected. Environmental factors acting upon the luminal bacteria including infectious agents, breast milk, and cigarette smoke exposure are of particular interest. The strongest predictor of IBD is a positive family history. However, the concordance rate for monozygotic twins is only 37% for CD and 10% for UC suggesting an environmental etiology combined with a familial predisposition.;Objective. To identify prenatal and early life risk factors for pediatric onset IBD, with an emphasis on birth characteristics, infections and cigarette smoke exposure.;Study design. We conducted a population-based, matched, case control study within the Kaiser Permanente Northern California membership to identify prenatal and early life risk factors for pediatric-onset IBD, with an emphasis on birth characteristics, infections and cigarette smoke exposure. We identified a large, representative cohort of 501 incident pediatric IBD cases receiving care at Kaiser Permanente since 1996. We utilized information from the computerized medical history to identify birth characteristics, infections and active cigarette smoke during the prenatal period and childhood before the onset of IBD. Conditional logistic regression was used.;Results. Infections and cigarette smoking play roles in the development of pediatric-onset IBD. No specific infection was identified to play a major role. Timing of the infection and initiation of cigarette smoking were important. No birth characteristic was strongly associated with IBD. Children with IBD were more likely to have mothers with IBD.;Implication. Future studies of risk factors for pediatric-onset IBD should consider the timing of infection and cigarette smoking initiation in addition to the presence or absence of the exposures. Infections and cigarette smoking initiation may play a role in the development of IBD. These exposures may also serve as markers of symptoms related to undiagnosed IBD.