Childhood exposure to environmental tobacco smoke and the risk of ulcerative colitis.

Previous reports have suggested that there may be a protective effect of active cigarette smoking on the risk of ulcerative colitis. Because passive smoking may also have other health consequences, the authors examined the effect of exposure to environmental tobacco smoke during childhood on adult risk of ulcerative colitis in a case-control study of 172 cases drawn in 1986-1987 from the rosters of North Carolina chapters of the Crohn's & Colitis Foundation of America and 131 peer-nominated neighborhood controls. Active smokers were less likely to develop ulcerative colitis than were nonexposed nonsmokers (odds ratio = 0.53, 95% confidence interval 0.24-1.14). The risk was also decreased in passive smokers, i.e., those whose parents had smoked (odds ratio = 0.50, 95% confidence interval 0.25-1.00). Risk estimates were not related to sex, education, age at onset of symptoms, or year of onset of symptoms. Both active smoking in adulthood and passive childhood exposure to environmental tobacco smoke appear to decrease the risk of ulcerative colitis. The results indicate that childhood passive smoke exposures can influence adult susceptibility to ulcerative colitis.