title: Autoimmune hepatitis: the role of environmental risk factors: a population-based study.
abstract: OBJECTIVE
  The etiology of autoimmune hepatitis (AIH) likely involves a complex interaction of genetic and environmental factors. We aim to investigate the associations between exposure to putative environmental factors and AIH and to quantify AIH risk in a first-degree relative.
  
  
  METHODS
  We conducted a population-based case-control study. Cases were AIH patients who were alive and resided in Canterbury, New Zealand, between 1 July 2011 and 30 June 2012. Controls were randomly selected from the Electoral Roll and were matched 2:1 to each case by age and gender. Self-reporting questionnaires that cover lifestyle factors, childhood factors and family history were used.
  
  
  RESULTS
  72 AIH cases and 144 controls were included. We found that exposure to antibiotics within 12 months prior to AIH diagnosis (OR 12.98, 95 % CI 2.49-67.67, p < 0.01) was an independent risk factor for the development of AIH. Alcohol consumption (OR 0.43, 95 % CI 0.28-0.68, p < 0.01) and childhood home with wood heating (OR 0.30, 95 % CI 0.14-0.63, p < 0.01) were independently associated with reduced risks of later development of AIH. The crude risk of AIH in first-degree relatives of a patient with AIH was 0.2 % (95 % CI <0.1-2.0).
  
  
  CONCLUSIONS
  We found that antibiotics are an independent risk factor for the development of AIH, whereas alcohol consumption and living in a childhood home with wood heating are independent protective factors against the later development of AIH.
authors.affiliation: University of Otago, Christchurch, Canterbury, New Zealand. jeffrey.ngu@cdhb.health.nz.|Department of Gastroenterology, Christchurch Hospital, Private Bag 4710, Christchurch, New Zealand. jeffrey.ngu@cdhb.health.nz.
authors.forename: Jing H
authors.initials: JH
authors.lastname: Ngu
authors.affiliation: University of Otago, Christchurch, Canterbury, New Zealand. richard.gearry@cdhb.health.nz.|Department of Gastroenterology, Christchurch Hospital, Private Bag 4710, Christchurch, New Zealand. richard.gearry@cdhb.health.nz.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Gearry
authors.affiliation: University of Otago, Christchurch, Canterbury, New Zealand. chris.frampton@otago.ac.nz.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Frampton
authors.affiliation: University of Otago, Christchurch, Canterbury, New Zealand. catherine.stedman@cdhb.health.nz.|Department of Gastroenterology, Christchurch Hospital, Private Bag 4710, Christchurch, New Zealand. catherine.stedman@cdhb.health.nz.
authors.forename: Catherine A M
authors.initials: CA
authors.lastname: Stedman
keywords: Autoimmune hepatitis; Environmental; Pathogenesis; Risk factors