title: Fine-scale geographic variations of inflammatory bowel disease in France: correlation with socioeconomic and house equipment variables.
abstract: BACKGROUND
  In a previous study we found a north-south gradient for Crohn's disease (CD) incidence in France. The aim of the present study was to determine if socioeconomic factors may influence the geographic distribution of CD and ulcerative colitis (UC) in France.
  
  
  METHODS
  Using the national health insurance databases, incidence rates of CD and UC were estimated for each of 341 metropolitan "job areas" in 2000-2002. Relationships between incidence rates and relevant contextual variables from the 1999 French census were tested for significance using a Poisson regression. Mapping of smoothed relative risks (sRR) for CD and UC at the scale of job areas, using a Bayesian approach and adjusting for significant contextual variables, was carried out in order to search for geographic variations.
  
  
  RESULTS
  CD incidence rates were negatively related to the percentage of farmers and to the percentage of housing with bathroom and toilets and positively related to the unemployment rate and to the percentage of households below the poverty threshold. Mapping of sRR for CD showed a clear north-south gradient, which was slightly improved after including the percentage of farmers and the percentage of housing with toilets. In UC we found no significant correlation between either incidence and socioeconomic variables or incidence and house equipment variables, and there was no north-south gradient. However, there was a positive and significant correlation between CD and UC incidence.
  
  
  CONCLUSIONS
  The present study shows that geographic risk factors of CD in France are northern latitude, nonrural areas, and areas with poor sanitary house equipment. Among these factors the most important is northern latitude.
authors.affiliation: *Pôle pharmaceutique, Centre Hospitalo-Universitaire, Besançon France, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Nerich
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Monnet
authors.forename: Alain
authors.initials: A
authors.lastname: Weill
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vallier
authors.forename: Vincent
authors.initials: V
authors.lastname: Vanbockstael
authors.forename: Guy-Robert
authors.initials: GR
authors.lastname: Auleley
authors.forename: Corine
authors.initials: C
authors.lastname: Balaire
authors.forename: Patrick
authors.initials: P
authors.lastname: Dubost
authors.forename: Stéphane
authors.initials: S
authors.lastname: Rican
authors.forename: Hubert
authors.initials: H
authors.lastname: Allemand
authors.forename: Franck
authors.initials: F
authors.lastname: Carbonnel
mesh_terms: D000328:Adult; D003093:Colitis, Ulcerative / Q000453:epidemiology*; D003424:Crohn Disease / Q000453:epidemiology*; D005260:Female; D005602:France / Q000453:epidemiology; D005828:Genetics, Population; D005843:Geography; D006798:Housing / Q000592:standards*; D006801:Humans; D015994:Incidence; D008297:Male; D009313:National Health Programs; D011379:Prognosis; D012307:Risk Factors; D012959:Socioeconomic Factors; D055815:Young Adult