The Association of Smoking and Surgery in Inflammatory Bowel Disease is Modified by Age at Diagnosis.
OBJECTIVE
We assessed the association of smoking at diagnosis of inflammatory bowel disease (IBD) on the need for an intestinal resection.


METHODS
The Health Improvement Network was used to identify an inception cohort of Crohn's disease (n=1519) and ulcerative colitis (n=3600) patients from 1999-2009. Poisson regression explored temporal trends for the proportion of newly diagnosed IBD patients who never smoked before their diagnosis and the risk of surgery within 3 years of diagnosis. Cox proportional hazard models assessed the association between smoking and surgery, and effect modification was explored for age at diagnosis.


RESULTS
The rate of never smokers increased by 3% per year for newly diagnosed Crohn's disease patients (incidence rate ratio (IRR) 1.03; 95% confidence interval (CI): 1.02-1.05), but not for ulcerative colitis. The rate of surgery decreased among Crohn's disease patients aged 17-40 years (IRR 0.96; 95% CI: 0.93-0.98), but not for ulcerative colitis. Smoking at diagnosis increased the risk of surgery for Crohn's disease patients diagnosed after the age of 40 (hazard ratio (HR) 2.99; 95% CI: 1.52-5.92), but not for those diagnosed before age 40. Ulcerative colitis patients diagnosed between the ages of 17 and 40 years and who quit smoking before their diagnosis were more likely to undergo a colectomy (ex-smoker vs. never smoker: HR 1.66; 95% CI: 1.04-2.66). The age-specific findings were consistent across sensitivity analyses for Crohn's disease, but not ulcerative colitis.


CONCLUSIONS
In this study, the association of smoking and surgical resection was dependent on the age at diagnosis of IBD.
Department of Medicine, University of Calgary, Calgary, Alberta, Canada.|Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.
Alexandra D
AD
Frolkis
Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.|Department of Pediatrics, University of Calgary, Calgary, Alberta, Canada.
Jennifer
J
de Bruyn
Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.|Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.
Nathalie
N
Jette
Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.|Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.
Mark
M
Lowerison
Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.|Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.
Jordan
J
Engbers
Department of Medicine, University of Calgary, Calgary, Alberta, Canada.|Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.
William
W
Ghali
Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
James D
JD
Lewis
Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.|Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.
Isabelle
I
Vallerand
Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.|Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.
Scott
S
Patten
Department of Medicine, University of Calgary, Calgary, Alberta, Canada.
Bertus
B
Eksteen
Department of Medicine, University of Calgary, Calgary, Alberta, Canada.|Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.
Cheryl
C
Barnabe
Department of Medicine, University of Calgary, Calgary, Alberta, Canada.
Remo
R
Panaccione
Department of Medicine, University of Calgary, Calgary, Alberta, Canada.
Subrata
S
Ghosh
Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.|Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.
Samuel
S
Wiebe
Department of Medicine, University of Calgary, Calgary, Alberta, Canada.|Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.
Gilaad G
GG
Kaplan