Trends in breast cancer incidence and mortality in Denmark, 1943-1982.

The trend in breast cancer incidence and mortality was examined using data from the Danish Cancer Registry and the national mortality statistics respectively. The study population comprised 65,870 incident cases and 33,817 deaths from breast cancer in Denmark between 1943 and 1982. The incidence rate remained almost constant up to around 1960, whereafter it rose steadily. Comparatively little change was observed in mortality. Possible explanations for the differing trends in incidence and mortality include under-reporting of breast cancer from death certificates and improvement in survival. A multivariate statistical analysis showed that the increase in incidence was due mostly to a cohort effect, though calendar time may have had a slight effect as well.