title: Smoking habit and load influence age at diagnosis and disease extent in ulcerative colitis.
abstract: BACKGROUND
  Cigarette smoking affects susceptibility to ulcerative colitis (UC), but its effects on age at diagnosis, disease extent, and need for surgery are less well defined. We examined these parameters in a detailed retrospective analysis of a large cohort of well-characterized UC patients.
  
  
  METHODS
  499 UC patients (254 male, median age 34.3 yr) were studied. Data were collected on smoking habits, smoking load (pack-years), age at recruitment, age at diagnosis, surgery, and disease extent. Colonoscopic and histological data at both diagnosis and follow-up (median follow-up time 4.6 yr) were available on 349 patients.
  
  
  RESULTS
  Ex-smokers were older at diagnosis than current or nonsmokers, (46.5 yr vs 31.1 or 29.4 yr, respectively, P < 0.001). Before diagnosis, ex-smokers had a higher smoking load than current smokers (13.0 vs 6.94 pack-years, P < 0.001). A Cox model for age at diagnosis, with smoking as a time-dependent covariate, showed that at any age, ex-smokers were significantly more likely to develop UC than current smokers (hazard ratio 1.8, 95% CI 1.41-2.44, P < 0.001). For current smokers at latest colonoscopy, those with extensive disease were the lightest smokers (median 0.320 pack-years), whereas those with healthy colons were the heaviest smokers (median 9.18 pack-years, P= 0.006). At 5 yr, regression of extensive disease was more frequent in current than ex-smokers or nonsmokers (30% current smokers vs 8% nonsmokers and 5% ex-smokers, chi(2)= 30.4, P < 0.001) but these differences were not maintained over a longer time period.
  
  
  CONCLUSIONS
  Smoking habit influences the age at diagnosis and changes in disease extent in UC. Mechanisms are likely to be complex and require further investigation.
authors.affiliation: Gastrointestinal Unit, Molecular Medicine Centre, School of Molecular and Clinical Medicine, University of Edinburgh, Western General Hospital, Edinburgh, Scotland, UK.
authors.forename: Marian C
authors.initials: MC
authors.lastname: Aldhous
authors.forename: Hazel E
authors.initials: HE
authors.lastname: Drummond
authors.forename: Niall
authors.initials: N
authors.lastname: Anderson
authors.forename: M Reza
authors.initials: MR
authors.lastname: Baneshi
authors.forename: Linda A
authors.initials: LA
authors.lastname: Smith
authors.forename: Ian D R
authors.initials: ID
authors.lastname: Arnott
authors.forename: Jack
authors.initials: J
authors.lastname: Satsangi
mesh_terms: D000328:Adult; D000367:Age Factors; D001706:Biopsy; D003093:Colitis, Ulcerative / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D003113:Colonoscopy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D011795:Surveys and Questionnaires