[Sex differential in life expectancy at birth in Japan: (2) trends in sex differential in life expectancy at birth from 1920 to 1990]

This study analyzed sex differentials in life expectancy at birth in Japan from 1920 to 1990, focusing on age structure and causes of death. Calculated life tables and vital statistics were mainly employed for the analysis. The results manifested that the sex differential in life expectancy at birth tended to increase throughout the period. Female/male ratios in life expectancy at birth had remained almost constant from 1960 to 1990 except 1975, though slight increase was observed in the recent decade. The sex differential in age-specific death rate in 0-4 year age group (particularly age 0) explained most of the sex differential in life expectancy at birth before 1947. After 1950, the age group of 60-79 played a major role in the sex differential in life expectancy at birth. It is noteworthy that female mortality exceeded male mortality in age groups of 2-41 before 1930. Consequently, excess of female mortality reduced the sex differential in life expectancy at birth at that period. As for the sex differential in mortality rates by causes of death, tuberculosis, pregnancy and childbirth related disease exerted a great influnece on decrease of the sex differential in life expectancy at birth before 1940. Recently, malignant neoplasm, heart diseases, cerebrovascular diseases, and accidents had become leading contributors to the sex differentials in life expectancy at birth.