Ecological risk factors for mortality from major malignant neoplasms by age and sex.

Japan has a unique position among industrialized countries as regards cancer mortality. For example, Japan is among the countries with the highest mortality from stomach cancer and the lowest for breast cancer1). Evidence has been given recently that some 80-90% of cancers can be related to environmental influences within a very broad definition2). Therefore, the international differences in cancer mortality can be ascribed to the effects of environmental as well as genetic factors. Thus, we have assumed that there are characteristic living mode effects on cancer mortality in Japan. Furthermore, the effects might be different among different age groups, as their lifestyles are not necessarily identical. We recently analyzed the effects of ecological factors on mortality rates from malignant neoplasms and on all causes of death in 46 prefectures in Japan3,4). The results indicated that urban residence was the principal factor affecting four of the five major malignant neoplasms, despite the fact that rural residence was the key factor affecting the total (malignant neoplasms and all other causes of death) mortality. In the present study, we analyze the age-specific effects of a wide variety of ecological factors on the mortality from major malignant neoplasms by stepwise regression analysis.