Smoking Is Not an Independent Risk Factor for Surgery in Patients with Crohn's Disease on Biologic Therapy.

Introduction: The development and course of inflammatory bowel disease appear to be influenced by environmental factors. Particularly, smoking has been shown to assume a harmful role in Crohn's disease (CD) and a protective role in ulcerative colitis. This study aims to examine the effect of smoking on need for surgery in patients with moderate to severe CD receiving biologic therapy.

Methods: This was a retrospective study of adult patients with CD at a University Medical Center over a 20-year period.

Results: A total of 251 patients were included (mean age 36.0 ± 15.0; 70.1% males; current, former, and nonsmokers: 44.2%, 11.6%, and 43.8%, respectively). Mean duration on biologics was 5.0 ± 3.1 years (>2/3 received anti-TNFs, followed by ustekinumab in 25.9%) and a third of patients (29.5%) received more than one biologic. Disease-related surgeries (abdominal, perianal, or both) occurred in 97 patients (38.6%): 50 patients had surgeries prior to starting biologics only, 41 had some surgeries after, and 6 had insufficient information. There was no significant difference in surgeries between ever-smokers (current or previous) versus nonsmokers in the overall study group. On logistic regression, the odds of having any CD surgery were higher in patients with longer disease duration (OR = 1.05, 95% CI = 1.01, 1.09) and in those receiving more than one biologic (OR = 2.31, 95% CI = 1.16, 4.59). However, among patients who had surgery prior to biologic therapy, smokers were more likely to have perianal surgery compared to nonsmokers (OR = 10.6, 95% CI = 2.0, 57.4; p = 0.006).

Conclusion: In biologic-naive CD patients requiring surgery, smoking is an independent predictor of perianal surgery. Smoking, however, is not an independent risk factor for surgery in this cohort after starting biologics. The risk of surgery in those patients is primarily associated with disease duration and the use of more than one biologic.