title: Increased ultraviolet light exposure is associated with reduced risk of inpatient surgery among patients with Crohn's disease.
abstract: OBJECTIVE
  Due to the formation of strictures and fistulas, patients with Crohn's disease (CD) frequently need surgery. Vitamin D has been found to play a role in the degree of inflammation. We aimed to study the effect of UV exposure on the need for inpatient surgery in patients with CD.
  
  
  METHODS
  The national inpatient sample, the largest database of hospitalizations from the USA, was used to conduct a retrospective study of patients hospitalized from 2004-2011 with CD by ICD-9CM code 555. Surgery was characterized as any intestinal surgery or fistula repair. An average state UV exposure was calculated for each hospitalization. Multivariate logistic regression was used to calculate the effect of UV exposure on surgery accounting for important covariates.
  
  
  RESULTS
  There were 481712 hospitalizations with a primary diagnosis of CD. Of these hospitalizations, 67751 included a relevant surgical procedure code. Mean UV exposure was statistically lower in the group undergoing surgery (4.3 units versus 4.4 units, p = 0.001). The ratio of hospitalizations per UV exposure tertile for CD was statistically different compared with all hospitalizations (p < 0.001). In univariate analysis, increased UV exposure was associated with a lower risk of inpatient surgery with an OR of 0.90 per unit (95% CI 0.84-0.96, p = 0.001). Accounting for age, gender, race/ethnicity, season, income, hospital setting, and Charlson-Deyo comorbidities, the effect of UV exposure remained protective for inpatient surgery (OR 0.91, 95% CI: 0.84-0.98, p = 0.01).
  
  
  CONCLUSIONS
  Increased UV exposure is associated with a reduced risk of inpatient surgery among patients with CD. Further studies of vitamin D's role in CD are necessary.
authors.affiliation: Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, MI, USA shailg@umich.edu.
authors.forename: Shail M
authors.initials: SM
authors.lastname: Govani
authors.affiliation: Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Peter D R
authors.initials: PD
authors.lastname: Higgins
authors.affiliation: Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Stidham
authors.affiliation: United States Army Research Institute of Environmental Medicine, Natick, MA, USA.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Montain
authors.affiliation: Department of Internal Medicine, Division of Gastroenterology, University of Michigan, Ann Arbor, MI, USA Veterans Affairs Center for Clinical Management Research, Ann Arbor, MI.
authors.forename: Akbar K
authors.initials: AK
authors.lastname: Waljee
mesh_terms: D000328:Adult; D003424:Crohn Disease / Q000601:surgery*; D013505:Digestive System Surgical Procedures; D005260:Female; D005500:Follow-Up Studies; D006760:Hospitalization / Q000639:trends; D006801:Humans; D015994:Incidence; D007297:Inpatients; D008297:Male; D011183:Postoperative Complications / Q000453:epidemiology / Q000517:prevention & control*; D011300:Preoperative Care / Q000379:methods*; D012189:Retrospective Studies; D012307:Risk Factors; D014466:Ultraviolet Rays; D014467:Ultraviolet Therapy / Q000379:methods*; D014481:United States / Q000453:epidemiology
keywords: Crohn’s disease; UV light; Vitamin D; surgery