title: Symptoms suggestive of cow's milk allergy in infancy and pediatric inflammatory bowel disease.
abstract: Risk factors of pediatric inflammatory bowel disease (PIBD) are incompletely understood. Recently, we reported that among patients with PIBD, a previous diagnosis of cow's milk allergy (CMA) and asthma occurred more frequently than among age- and sex-matched peers. We tested at a national level the hypothesis that CMA is associated with the risk of contracting PIBD.
  
  
  
  A nationwide birth cohort (n = 225,041), including all Finnish children born between 1999 and 2002, was followed up until July 1, 2014. We identified all children with a diagnosis of CMA, asthma, and PIBD from a national register; the data were based on certificates, including diagnostic criteria. The 95% confidence intervals (CI) for the incidence rates per 100,000 person-years were calculated assuming a Poisson distribution.
  
  
  
  We identified 7,910 infants with CMA yielding a cumulative incidence of 3.5% by 2 years of age. The cumulative incidence of PIBD was 0.14% (n = 316) and that of asthma 6.6% (14,807). Children with CMA were more likely to develop PIBD than non-CMA children, incidence ratio 2.6 (95% CI 1.7-3.8). Children with a diagnosis of CMA contracted PIBD at a younger age than the respective non-CMA group (9 vs. 11 years, p < 0.05). The risk was more evident for ulcerative colitis than for Crohn's disease. The association between CMA and asthma was stronger than that between CMA and PIBD.
  
  
  
  CMA in infancy is associated with subsequent development of asthma and PIBD. This suggests that in a subgroup of patients, CMA may share underlying background with PIBD, warranting thorough follow-up.
authors.affiliation: Research Department, Social Insurance Institution of Finland, Turku, Finland.
authors.forename: Lauri J
authors.initials: LJ
authors.lastname: Virta
authors.affiliation: Unit of Primary Health Care, Helsinki University Hospital, Helsinki, Finland.|Department of General Practice, University of Helsinki, Helsinki, Finland.|Unit of Primary Health Care, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Hannu
authors.initials: H
authors.lastname: Kautiainen
authors.affiliation: Children's Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland.
authors.forename: Kaija-Leena
authors.initials: KL
authors.lastname: Kolho
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D017668:Age of Onset; D000900:Anti-Bacterial Agents / Q000009:adverse effects; D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D003093:Colitis, Ulcerative / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology; D003424:Crohn Disease / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D016269:Milk Hypersensitivity / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents
keywords: Crohn's disease; antibiotics; asthma; children; ulcerative colitis