title: Microbial exposure in infancy and subsequent appearance of type 1 diabetes mellitus-associated autoantibodies: a cohort study.
abstract: OBJECTIVE
  The role of microbial exposure during early life in the development of type 1 diabetes mellitus is unclear.
  
  
  OBJECTIVE
  To investigate whether animal contact and other microbial exposures during infancy are associated with the development of preclinical and clinical type 1 diabetes.
  
  
  METHODS
  A birth cohort of children with HLA antigen-DQB1-conferred susceptibility to type 1 diabetes was examined. Participants included 3143 consecutively born children at 2 hospitals in Finland between 1996 and 2004.
  
  
  METHODS
  The following exposures during the first year of life were assessed: indoor and outdoor dogs and cats, farm animals, farming, visit to a stable, day care, and exposure to antibiotics during the first week of life.
  
  
  METHODS
  Clinical and preclinical type 1 diabetes were used as outcomes. The latter was defined as repeated positivity for islet-cell antibodies plus for at least 1 of 3 other diabetes-associated autoantibodies analyzed and/or clinical type 1 diabetes. The autoantibodies were analyzed at 3- to 12-month intervals since the birth of the child.
  
  
  RESULTS
  Children exposed to an indoor dog, compared with otherwise similar children without an indoor dog exposure, had a reduced odds of developing preclinical type 1 diabetes (adjusted odds ratio [OR], 0.47; 95% CI, 0.28-0.80; P = .005) and clinical type 1 diabetes (adjusted OR, 0.40; 95% CI, 0.14-1.14; P = .08). All of the other microbial exposures studied were not associated with preclinical or clinical diabetes: the odds ratios ranged from 0.74 to 1.58.
  
  
  CONCLUSIONS
  Among the 9 early microbial exposures studied, only the indoor dog exposure during the first year of life was inversely associated with the development of preclinical type 1 diabetes. This finding needs to be confirmed in other populations.
authors: The National Institute for Health and Welfare, Nutrition Unit, Helsinki, Finland2Center for Child Health Research, University of Tampere and Tampere University Hospital, Tampere, Finland3The Science Center of Pirkanmaa Hospital District, Tampere, Finland4.
authors: Suvi M
authors: SM
authors: Virtanen
authors: The National Institute for Health and Welfare, Nutrition Unit, Helsinki, Finland4School of Health Sciences, University of Tampere, Tampere, Finland.
authors: Hanna-Mari
authors: HM
authors: Takkinen
authors: School of Health Sciences, University of Tampere, Tampere, Finland.
authors: Bright I
authors: BI
authors: Nwaru
authors: Center for Child Health Research, University of Tampere and Tampere University Hospital, Tampere, Finland5University of Helsinki, Hjelt Institute, Helsinki, Finland.
authors: Minna
authors: M
authors: Kaila
authors: The National Institute for Health and Welfare, Nutrition Unit, Helsinki, Finland3The Science Center of Pirkanmaa Hospital District, Tampere, Finland4School of Health Sciences, University of Tampere, Tampere, Finland.
authors: Suvi
authors: S
authors: Ahonen
authors: Department of Statistics, Faculty of Mathematics and Natural Sciences, University of Turku, Turku, Finland.
authors: Jaakko
authors: J
authors: Nevalainen
authors: The National Institute for Health and Welfare, Nutrition Unit, Helsinki, Finland.
authors: Sari
authors: S
authors: Niinistö
authors: Children's Hospital, University of Helsinki, and University Central Hospital, Helsinki, Finland8University of Helsinki, Diabetes and Obesity Research Program, Helsinki, Finland.
authors: Heli
authors: H
authors: Siljander
authors: Department of Pediatrics, Faculty of Medicine, University of Turku, Turku, Finland.
authors: Olli
authors: O
authors: Simell
authors: Immunogenetics Laboratory, University of Turku, Turku, Finland11Department of Clinical Microbiology, Faculty of Health Sciences, University of Eastern Finland, Kuopio.
authors: Jorma
authors: J
authors: Ilonen
authors: School of Medicine, University of Tampere, Tampere, Finland.
authors: Heikki
authors: H
authors: Hyöty
authors: Department of Pediatrics, University of Oulu, Oulu, Finland.
authors: Riitta
authors: R
authors: Veijola
authors: Center for Child Health Research, University of Tampere and Tampere University Hospital, Tampere, Finland7Children's Hospital, University of Helsinki, and University Central Hospital, Helsinki, Finland8University of Helsinki, Diabetes and Obesity Research.
authors: Mikael
authors: M
authors: Knip
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000009:adverse effects; D001323:Autoantibodies / Q000097:blood*; D015551:Autoimmunity; D002415:Cats; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology / Q000235:genetics / Q000276:immunology*; D004285:Dogs; D004781:Environmental Exposure; D005260:Female; D005387:Finland / Q000453:epidemiology; D020022:Genetic Predisposition to Disease; D006680:HLA Antigens / Q000235:genetics; D006801:Humans; D006920:Hygiene; D007223:Infant; D007231:Infant, Newborn; D007515:Islets of Langerhans / Q000276:immunology; D008297:Male; D064307:Microbiota; D012307:Risk Factors; D011795:Surveys and Questionnaires
chemical_list: D000890:Anti-Infective Agents; D001323:Autoantibodies; D006680:HLA Antigens