Increased Ultraviolet Light Exposure is Associated With Reduced Risk of Inpatient Surgery Among Patients With Crohn's Disease

Background and aims: 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 481 712 hospitalizations with a primary diagnosis of CD. Of these hospitalizations, 67 751 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.