title: High residential sun exposure is associated with a low risk of incident Crohn's disease in the prospective E3N cohort.
abstract: BACKGROUND
  Vitamin D insufficiency has been suggested to be associated with high risk of Crohn's disease (CD). In France, where food fortification is limited, the major source of vitamin D is through sun exposure. The aim of this work was to analyze the relationship between residential sun exposure and the risk of incident CD or ulcerative colitis (UC).
  
  
  METHODS
  The E3N cohort consists of women living in France, aged 40 to 65 years and free of major diseases at inclusion in 1990. Among the 91,870 women included in the study, we identified 123 incident cases (45 CD, 71 UC, and 7 indeterminate colitis). To assess residential sun exposure, we used a database containing mean daily ultraviolet radiation (UVR) dose for each French county. The relationship between residential sun exposure and risk of incident inflammatory bowel diseases was explored using Cox models.
  
  
  RESULTS
  Higher levels of residential sun exposure were associated with a significant decreased risk of CD (hazard ratio [HR] for the third versus the first tertile of UVR dose, 0.49; 95% confidence interval (CI), 0.23-1.01; P for trend = 0.04), but not of UC (HR, 1.21; CI, 0.61-2.11). In women with available data on dietary vitamin D intake, we observed a lower risk of CD with higher residential UVR (HR, 0.29; 95% CI, 0.11-0.80; P for trend = 0.01). Dietary vitamin D intake was neither associated with the risk of CD (HR, 0.41; 95% CI, 0.14-1.24; P for trend = 0.14) nor UC (HR, 1.61; CI, 0.61-4.23).
  
  
  CONCLUSIONS
  In this prospective cohort of women, high residential sunlight exposure was associated with decreased incidence of CD, but not UC.
authors.affiliation: *Inserm, Centre for Research in Epidemiology and Population Health (CESP), U1018, Nutrition, Hormones and Women's Health Team, Villejuif, France; †Univ Paris Sud, UMRS 1018, Villejuif, France; ‡Inserm U1018, Institut Gustave Roussy, Villejuif, France; §Sainte Justine University Hospital, Montréal, Canada; and ‖Service de Gastroentérologie, Hôpitaux Universitaires Paris Sud, CHU de Bicêtre, APHP, Le Kremlin Bicêtre, France.
authors.forename: Prévost
authors.initials: P
authors.lastname: Jantchou
authors.forename: Francoise
authors.initials: F
authors.lastname: Clavel-Chapelon
authors.forename: Antoine
authors.initials: A
authors.lastname: Racine
authors.forename: Marina
authors.initials: M
authors.lastname: Kvaskoff
authors.forename: Franck
authors.initials: F
authors.lastname: Carbonnel
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Boutron-Ruault
mesh_terms: D000328:Adult; D000368:Aged; D003093:Colitis, Ulcerative / Q000453:epidemiology* / Q000378:metabolism; D003424:Crohn Disease / Q000453:epidemiology* / Q000378:metabolism; D004032:Diet; D015444:Exercise; D005260:Female; D005500:Follow-Up Studies; D005602:France / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D012111:Residence Characteristics; D012307:Risk Factors; D012867:Skin / Q000528:radiation effects*; D013472:Sunlight; D011795:Surveys and Questionnaires; D014807:Vitamin D / Q000378:metabolism*
chemical_list: D014807:Vitamin D