What is the correlation between smoking and Inflammatory Bowel Disease (IBD)?

Smoking and IBD: Contrasting Effects on Crohn's Disease and Ulcerative Colitis

Smoking has opposite effects on the two major forms of IBD: it worsens Crohn's disease outcomes while appearing protective in ulcerative colitis, making smoking cessation essential for Crohn's disease patients but potentially problematic for those with ulcerative colitis. 1

Effects of Smoking on Crohn's Disease

Negative Impact on Disease Course

• Smoking is more common in patients diagnosed with Crohn's disease, particularly in those diagnosed after age 40 (47% prevalence vs. 27% in background population) 1
• Continued smoking results in:
  • Worse disease course compared to non-smokers or those who quit
  • Higher risk of disease flares
  • Increased incidence of surgery
  • Worse outcomes after surgery (2.5-fold increase in risk of repeat surgery)
  • 2-fold increased risk of clinical recurrence 1

Important Considerations

• Even passive smoking and light smoking (<10 cigarettes/day) are as harmful as heavy smoking
• Smoking effects are more pronounced in women than men with Crohn's disease
• Smoking increases surgical complications for all colorectal surgeries 1

Effects of Smoking on Ulcerative Colitis

Paradoxical Protective Effect

• UC is more common in non-smokers
• UC is more likely to arise in those who recently quit smoking (highest risk period: 2-5 years after stopping)
• UC patients who smoke experience:
  • Reduced colectomy rates
  • Less primary sclerosing cholangitis
  • Less back-wash ileitis
  • Less extensive disease with higher cigarette consumption
  • Reduced need for therapy 1

Smoking Cessation in UC

• UC patients who quit smoking have a significantly worse disease course than those who continue
• Increased need for corticosteroids and azathioprine
• Higher hospitalization rates 1

Clinical Management Recommendations

For Crohn's Disease Patients

• All Crohn's disease patients who smoke should be strongly encouraged to stop smoking, as this significantly improves disease outcomes and reduces complications. 1
• Benefits of quitting accrue at any stage of Crohn's disease
• Active smoking cessation measures should be employed:
  • Behavioral therapy (e.g., cognitive behavioral therapy)
  • Pharmacotherapy (nicotine replacement, bupropion, varenicline)
  • The TABACROHN study showed 31% of patients quit initially, with 23% still abstinent after 18 months 1

For Ulcerative Colitis Patients

• UC patients who smoke should still be encouraged to stop for general health benefits
• Patients should be warned about the increased risk of disease flare after smoking cessation
• Medication adjustments may be required to control disease after smoking cessation 1

Practical Approach to Smoking Cessation in IBD

1. Assessment: Identify all IBD patients who smoke
2. Education: Explain disease-specific effects of smoking
3. Intervention:
   • Refer to smoking cessation services
   • Combine behavioral therapy with pharmacotherapy
   • Consider setting up dedicated smoking cessation services for IBD patients (cost-effective due to reduced disease management costs) 1
4. Follow-up: Monitor disease activity closely after smoking cessation, especially in UC patients

Important Caveats

• Despite the apparent protective effect in UC, the overall health risks of smoking outweigh any disease-specific benefits
• Education about the relationship between smoking and IBD appears inadequate, as cessation rates after diagnosis are similar between CD and UC patients 2
• Higher education levels are associated with better smoking cessation rates in both CD and UC patients 2
• The mechanisms behind these opposing effects remain unclear but may involve nicotine's effects on gut immunity and microbiota 3, 4

By addressing smoking status and providing appropriate cessation support, clinicians can significantly improve outcomes for patients with Crohn's disease while managing potential disease flares in those with ulcerative colitis who quit smoking.