[Current status and trends in cancer mortality in Japan]

Trends of cancer mortality in Japan were reviewed in comparison with all-cause mortality, by major sites and age groups. The proportion of cancer mortality to all-cause mortality is on the increase among young children, and the middle-aged population, due to the decreased mortality other than cancer. The number of deaths from cancer is still on the increase, mainly due to the aging population. But the age-standardized rates now seem to be leveling off among males and bottoming out for females. The trends are not simple, because the cancer mortality has been influenced by many factors such as the rapidly aging population or the drastic change in the social situation after World War II. In lung or liver cancer, the apparent birth cohort effect was observed; there were birth cohorts suggested to have lower or higher cancer mortality. Such birth cohort effects were related to the trends in strong risk factor such as tobacco smoking or hepatitis virus, and thus may influence the trends of cancer mortality. Therefore, on estimating the future trends of cancer mortality in Japan, it is important to take into account such trends in risk factors.