[Trend analysis in Hodgkin disease mortality in the German Federal Republic 1955-1989: a comparison of log-linear models with descriptive standard methods].

Age-Period-Cohort (APC) models have become a widely accepted method to analyse incidence and mortality rates of cancer or other diseases. In this paper we compare simple descriptive methods such as plotting age-specific rates and standardized rates with regression models in order to investigate mortality rates of Morbus Hodgkin's disease in Germany (West-Germany) between 1955 and 1989. With any of the approaches it can be seen that the mortality of Morbus Hodgkin's disease has been decreasing around 1970. Although APC-models allow some detailed investigation of the separate influence of the age, period and cohort effect, the results are difficult to interpret as there is no unique solution for the parameter estimates (identification problem of APC-models). For the mortality of Morbus Hodgkin's, the result of the APC-modelling shows that the decrease of mortality is overestimated if the cohort effect is not taken into consideration. We therefore conclude that the interpretation of the APC-model should be done in connection with other methods to avoid misinterpretation. The combination of both approaches will lead to a better understanding of the incidence or mortality patterns of cancer.