Lifestyle and Cancer after the Second World War in Japan

Abstract

In this article, the changes in lifestyle and in the mortality rates of lifestyle-related cancers of Japanese people are discussed from the viewpoint of descriptive epidemiology. In Japan, stomach cancer was formerly one of the most frequent causes of cancer death. Colorectal, pancreas, breast and prostate cancers were not frequent. Thus, the kinds of cancer that Japanese people contracted were different from those in western countries. However, after the Second World War, the crude mortality rate of colorectal cancer increased, and in 1992 it became higher than that in the USA. The age-adjusted mortality rates of colorectal, pancreas, breast and prostate cancers increased, and that of stomach cancer gradually decreased. That is, the kinds of cancer of Japanese people have been westernized. In Japan, during the 70 years after the Second World War, the lifestyle, especially eating habits, greatly changed. Before the war the Japanese people ate much plant food, but after the war, the percentage of the intake of animal protein and animal fat greatly increased due to increased consumption of meat and poultry. The changes in the age-adjusted mortality rates of colorectal, pancreas and prostate cancers after the war can be at least partially accounted for by the change in eating habits. In Japan, the smoking rate was the highest for both males and females in 1966, and thereafter it has been decreasing. The age-adjusted mortality rate of lung cancer increased until 1995, but has been decreasing since that year. Since there is an interval of about 30 years between them, the "latent period" of smoking for lung cancer seems to be about 30 years. The mean age of women's first marriage and that of the first delivery have both increased and may be factors contributing to the constant increase of the age-adjusted mortality of breast cancer.