title: Low exposure to sunlight is a risk factor for Crohn's disease.
abstract: BACKGROUND
  Low sunshine exposure might contribute to the pathogenesis of inflammatory bowel disease (IBD).
  
  
  OBJECTIVE
  To assess the geographic distribution of IBD incidence in relation to sunshine exposure in France to test the hypothesis that higher sun exposure is associated with lower IBD risk.
  
  
  METHODS
  Using the national health insurance database, incidence rates of Crohn's disease (CD) and ulcerative colitis (UC) were estimated for each of the 94 French administrative areas ('départements'), between 2000 and 2002. The surface UV radiation intensity was obtained by combining modelling and satellite data from Meteosat, the European meteorological satellite. Relationships between incidence rates and sun exposure were tested for significance by using a Poisson regression. We mapped smoothed relative risks (sRR) for CD and UC, using a Bayesian approach and adjusting for sun exposure, to search for geographical variations.
  
  
  RESULTS
  Areas with a smoothed RR of CD incidence significantly above 1 corresponded to areas with low sunshine exposure, whereas those with high or medium sunlight exposure had smoothed RRs either lower than 1 or not significantly different from 1. There was no association between sun exposure and UC incidence.
  
  
  CONCLUSIONS
  This geographic study suggests that low sunlight exposure is associated with an increased incidence of Crohn's disease. Further studies are needed to determine if this association is causal.
authors.affiliation: Pôle pharmaceutique, University Hospital, Besançon, France. v1nerich@chu-besancon.fr
authors.forename: V
authors.initials: V
authors.lastname: Nerich
authors.forename: P
authors.initials: P
authors.lastname: Jantchou
authors.forename: M-C
authors.initials: MC
authors.lastname: Boutron-Ruault
authors.forename: E
authors.initials: E
authors.lastname: Monnet
authors.forename: A
authors.initials: A
authors.lastname: Weill
authors.forename: V
authors.initials: V
authors.lastname: Vanbockstael
authors.forename: G-R
authors.initials: GR
authors.lastname: Auleley
authors.forename: C
authors.initials: C
authors.lastname: Balaire
authors.forename: P
authors.initials: P
authors.lastname: Dubost
authors.forename: S
authors.initials: S
authors.lastname: Rican
authors.forename: H
authors.initials: H
authors.lastname: Allemand
authors.forename: F
authors.initials: F
authors.lastname: Carbonnel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001499:Bayes Theorem; D003093:Colitis, Ulcerative / Q000453:epidemiology; D003424:Crohn Disease / Q000453:epidemiology*; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013472:Sunlight