Smoking in inflammatory bowel diseases: Good, bad or ugly?

Table 1 Smoking in IBD: Practice points

Ulcerative colitis (UC)	Crohn’s disease (CD)
Current smoking decreases the risk for UC by app. 50%, in contrast former smoking is associated with an app. 2-fold increased risk	Both current and former smoking (presumable also passive smoke exposure during childhood) increases the risk of CD almost 2-fold
The protective effect is smaller in females	The risk is greater in females compared with males
Proximal extension of the disease is less likely in smokers as well as disease course is milder but the risk of lung cancer and vascular disease is higher	Smoking is associated with complicated (stricturing or penetrating) and ileal disease
Patients who stop smoking experience an increase in disease activity at least during the first year after cessation	Smokers with CD need more steroids, more immunosuppressants and more operations than non-smokers
The effect of smoking is similar in indeterminate colitis (less evidence is available)	Smoking cessation improves rapidly the course of CD
Nicotine-replacement therapies and antidepressants are useful in heavy smokers motivated to stop smoking Geographic differences exists (e.g. Israel, Korea)