Comparison of Trends in Cancer Incidence and Mortality in Osaka, Japan, Using an Age-Period-Cohort Model

Background. We aimed to estimate the effects of age, period and birth cohort on trends in cancer incidenceand death for all sites and selected sites of cancer in Osaka using an age-period-cohort model. Methods. Cancerincidence data during 1968-2003 were obtained from the Osaka Cancer Registry, and cancer mortality withpopulation data in Osaka during 1968-2007 were obtained from vital statistics departments. We estimated age,period and birth cohort effects for incidence and mortality using Nakamura’s Bayesian Poisson age-periodcohortmodel. Results. For most sites of cancer, linear ageing effects were observed, the exceptions being breastand cervix which levelled-off at around 40 years old, while period effects were small. Decreasing cohort effectswere observed in stomach and liver cancer. Cohort effects peaked at the generation born in the early 1950sfor colorectal, lung, breast cancers. For most sites of cancer, incidence and mortality showed similar trends,but in the late cohorts for cervical cancer, cohort effects decreased in mortality, while increasing in incidence.Conclusion. Period effects reflecting immediate effects to cancer incidence and mortality, such as developmentof the effective treatment and screening programme were stable in most sites of cancer. Cohort effects influencedby long-term risk factors were prominently observed for every site, decrease in stomach and liver cancer casesbeing related to reduction in risk factor prevalence. Cancer control activities could be evaluated through theresults, indicating utility for future cancer control planning.