Abstract
From about the springtime of 1980 in Japan the problem about the sudden increase of deaths of middle aged persons born in the period from 1927 (Showa 2) to 1934 (Showa 9) has been much talked in some parts of society. With the object of clarifying the propriety of this problem the present writers and the joint researcher selected "Vital Statistics" as the data of this study. Using these data each cohort group by sex who became 35 years of age in the following 3 terms such as agreeing with the object of the study was set up. (1) We historically intended to compare the trends of cohort deaths of middle aged persons by sex born in the period from 1927 to 1934 with those of cohort deaths of another cohort groups. (1): 1899-1908, (2): 1920-1951, (3): 1962-1967 (2) At the same time we tried to find out restrictions et cetra on making use of statistics by comparison between the trend of the above mentioned cohort deaths and that of period deaths by each year in the same terms. In consequence, referring to (1) the range of age which shows the similar ascending tendency as the trend of dx-curves is wider in males than in females. In case of being observed these ascending phenomena in quality, however, it couldn't be recognized that deaths of middle aged persons born in the period from 1927 to 1934 are increasing more than that of other annual cohort groups. Respecting to (2) it became clear that a prudent attitude should be needed, especially within a definite range of age, in using the way of thinking of Period Life Table.
