title: Is current smoking still an important environmental factor in inflammatory bowel diseases? Results from a population-based incident cohort.
abstract: BACKGROUND
  Previous studies suggest that smoking is an important environmental factor in inflammatory bowel diseases (IBDs), with dichotomous effects in ulcerative colitis (UC) and Crohn's disease (CD). The aim of this study was to analyze the relationship between smoking and IBD risk in a population-based database from Veszprem Province, which included incident cases diagnosed between January 1, 1977, and December 31, 2008.
  
  
  METHODS
  Data from 1420 incident patients were analyzed (UC: 914, age at diagnosis: 38.9 years; CD: 506, age at diagnosis: 31.5 years). Both inpatient and outpatient records were collected and comprehensively reviewed. Overall, smoking frequency in the adult general population was 36.1%.
  
  
  RESULTS
  Of patients with CD, 47.2% were current smokers at diagnosis. Smoking was more frequent in male patients (P = 0.002) and was associated with an increased risk of CD (odds ratio, 1.96; 95% confidence interval, 1.63-2.37; P < 0.001). In contrast, current smoking was protective against UC (odds ratio, 0.33; 95% confidence interval, 0.27-0.41). The effect of smoking was linked to gender (in CD, more deleterious in male patients) and age at diagnosis and was most prominent in young adults, with a difference already being seen in 18- to 19-year-olds. In CD, a change in disease behavior (P = 0.02), location from ileal or colonic to ileocolonic (P = 0.003), arthritis/arthropathy (P = 0.002), need for steroids (P = 0.06), or AZA (P = 0.038) was more common in current smokers. Smoking in UC was associated with more extensive disease (P = 0.01) and a tendency for decreased need for colectomy (P = 0.06).
  
  
  CONCLUSIONS
  Current smoking was associated with the risk of IBD. This effect was linked to gender and age at diagnosis and was most prominent in young adults. No association was observed in pediatric or elderly patients. The deleterious and protective effects of smoking on the course in CD and UC were partially confirmed.
authors: 1st Department of Medicine, Semmelweis University, Budapest, Hungary. lakatos.peter_laszlo@med.semmelweis-univ.hu
authors: Peter L
authors: PL
authors: Lakatos
authors: Zsuzsanna
authors: Z
authors: Vegh
authors: Barbara D
authors: BD
authors: Lovasz
authors: Gyula
authors: G
authors: David
authors: Tunde
authors: T
authors: Pandur
authors: Zsuzsanna
authors: Z
authors: Erdelyi
authors: Istvan
authors: I
authors: Szita
authors: Gabor
authors: G
authors: Mester
authors: Mihaly
authors: M
authors: Balogh
authors: Istvan
authors: I
authors: Szipocs
authors: Csaba
authors: C
authors: Molnar
authors: Erzsebet
authors: E
authors: Komaromi
authors: Petra A
authors: PA
authors: Golovics
authors: Michael
authors: M
authors: Mandel
authors: Agnes
authors: A
authors: Horvath
authors: Miklos
authors: M
authors: Szathmari
authors: Lajos S
authors: LS
authors: Kiss
authors: Laszlo
authors: L
authors: Lakatos
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003093:Colitis, Ulcerative / Q000453:epidemiology / Q000209:etiology*; D003424:Crohn Disease / Q000453:epidemiology / Q000209:etiology*; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006814:Hungary / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D055815:Young Adult