[Cigarette smoking and ulcerative colitis--is there a causal relationship?].

The relation between cigarette smoking and ulcerative colitis was assessed in a case-control study of 235 cases of ulcerative colitis and 311 age- and sex-matched control subjects admitted to the hospital for conditions unrelated to smoking. Smoking habits and daily number of cigarettes smoked were analysed. We found significantly less number of smokers and more ex-smokers in the ulcerative colitis group. The intensity of smoking was equal in both groups. It was noted that pancolitis occurred more frequently in the ex-smokers group. The intensity of smoking did not influence the extension and clinical course of ulcerative colitis. For ulcerative colitis, the relative risk for nonsmokers was 7.4. The study revealed a positive correlation between nonsmoking and ulcerative colitis, higher incidence of pancolitis among ex-smokers and higher relative risk of ulcerative colitis for never-smokers. Various possible causes of influence of smoking on ulcerative colitis are discussed.