Colorectal cancer in Denmark 1943-1988.

Nation-wide incidence rates are presented of colorectal cancer in Denmark from 1943 to 1988. In Denmark notification of malignant and related diseases is mandatory. The percentage of histologically confirmed tumours is now 95. The annual incidence rate of colon cancer in Denmark has been increasing among men and women combined from 684 cases in 1943-47 to 2020 cases in 1988. In the same period the incidence of rectal cancer has been increasing from 762 cases in 1943-47 to 1108 cases in 1988. We analyzed the effects of age, calendar time, and birth cohort with multiplicative Poisson models. We did not find consistent period effects in the models. We suggest the trends in colorectal cancer incidence rates may be due to changes in environmental factors such as dietary habits and in physical activity. Furthermore, we suggest an etiologic distinction between carcinoma of the rectum, the left colon and the right colon.