: An inverse relation between
appendectomy and
ulcerative colitis and smoking and
ulcerative colitis has been proposed. Our study examined the frequency of common surgical interventions and of smoking in 500 patients with
inflammatory bowel disease. They comprised 177 patients with
ulcerative colitis, 134 patients with
Crohn's disease, and 189 controls matched for age, sex, and socioeconomic group. Subjects were questioned on all previous surgery and on smoking history. The
appendectomy rate among controls was 17.5% (33 of 189), which was significantly greater than that of patients with
ulcerative colitis: 8.5% (15 of 177; p < 0.05). However, after using multiple variable logistic regression analysis, this was no longer statistically significant. There was no significant difference in
appendectomy rate between patients with
Crohn's disease and controls. The three groups had comparable rates of
tonsillectomy and
cholecystectomy. Of patients with
ulcerative colitis, 84.2% were nonsmokers at the time of diagnosis in contrast to 50.4% among the patients with
Crohn's disease (p < 0.01). In this case-control study, by using multivariate logistic regression analysis,
appendectomy offers no significant protection from developing
ulcerative colitis or
Crohn's disease. Smoking appears to be deleterious in
Crohn's disease, whereas a cessation of smoking precedes the onset of
ulcerative colitis in a significant number of cases.