Abnormal Trend in Mortalities for Birth Cohorts Born in Around 1930 Year

Abstract

Abnormal trend in mortalities of cohorts born in the early Showa Era was reported by Okubo and others based on quinquennial mortalities of 5-year birth cohort . However, the results of those studies not always coincide in birth cohorts and causes of death for which abnormal trends were noticed. In this study cohort mortalities were calculated for single year birth cohort from 1950 through 1985 and analysed. Abnormal trend in mortalities for around 1930 birth cohorts were clearly observed among males, starting at age of 35 years, in general, as a poor improvement of mortality for all causes and many of the main chronic degenerative diseases. An extent of cohorts and causes of death for which abnormal trends were observed were fully examined. As to the cohort abnormal trends were observed in 1927 to 1932 born cohorts, 1929 and 1931 as a focus. In causes of death all causes, malignant neoplasms (all sites, stomach and lung), cerebrovascular diseases, heart diseases, chronic liver diseases and cirrhosis, and diabetes mellitus showed abnormal trends. Similar but weak trends were seen for ulcer of the stomach and duodenum, and suicide but there noticed stronger period effects than cohort's. Factors related to those abnormal trends of mortalities remained undefined but supposedly susceptibilities for those diseases might have been induced by poor nutritional conditions prevailed during their midteen's, the second growth accelerating period, due to the social and economic chaos just after the World War II. Controus maps method used in this study gave clearer visual images for age, period, and cohort effects and is useful in mortality analysis.