Exposure to risk factors for ulcerative colitis occurs during an early period of life.

OBJECTIVE: It has been speculated that environmental factors play a role in the etiology of ulcerative colitis. A previous analysis revealed that the time trends of ulcerative colitis in England were shaped by an underlying birth-cohort pattern. We undertook this study to test whether the birth-cohort pattern was a unique feature of the English vital statistics or whether a similar phenomenon could also be ascertained in the mortality statistics from a different country, such as Switzerland. Besides comparing the data of ulcerative colitis from Switzerland and England, the trends of ulcerative colitis were compared with those of gastric and duodenal ulcer.
METHODS: Death rates from ulcerative colitis, gastric ulcer, and duodenal ulcer were plotted against the period of death and period of birth. An age-standardized cohort mortality ratio was calculated as a summary statistic of the overall mortality associated with each consecutive birth-cohort.
RESULTS: Mortality from ulcerative colitis increased among successive generations born throughout the 19th century. It peaked in individuals born around 1890 and has declined since then. Strikingly similar patterns were found in Switzerland and England. The birth-cohort pattern underlying the time trends of ulcerative colitis applied equally to the data for women and men. In comparison with peptic ulcer, the birth-cohort pattern of ulcerative colitis was almost identical to that of duodenal ulcer. It peaked in both countries 10-20 yr later than gastric ulcer.
CONCLUSIONS: The birth-cohort pattern indicates that acquisition of ulcerative colitis is strongly influenced by environmental risk factors and that the exposure to these factors occurs during an early period of life. The similarity in the birth-cohort patterns of duodenal ulcer and ulcerative colitis could hint at a childhood infection or a related mode of transmission in both diseases.