Effects of cigarette smoking on the long-term course of Crohn's disease

In Crohn's disease, smoking increases the risk for surgical procedures. The influence of smoking on the overall severity of the disease remains controversial. The purpose of the study was to examine the effects of smoking on the long-term course of Crohn's disease and the relationship between smoking and therapy.

The medical charts of 400 consecutive patients whose smoking habits were specified by direct interview were reviewed.

Frequency and extent of excisional surgery were not significantly different in smokers and nonsmokers, but smokers required more glucocorticoids and immunosuppressive drugs. The effect of smoking on the need for immunosuppressive drugs was dose-dependent and was significant in women but not in men. For female smokers, the 10-year risk of immunosuppressive therapy was 52% +/- 11% compared with 24% +/- 10% for nonsmokers (P < 0.001). The risk of surgery increased only in patients who smoked and did not take immunosuppressive drugs. The surgical rate increased significantly during smoking in 19 patients who started smoking after diagnosis and decreased significantly in 34 patients who stopped compared with matched controls.

Patients who smoke, particularly women and heavy smokers, run a high risk of developing severe disease. Immunosuppressive therapy neutralizes the influence of smoking on surgical rates.