Sex differential in life expectancy in Japan and Scotland: age and causes of death.

The contribution of age groups and causes of death to the sex difference in life expectancy (SDLE) at birth in Japan and Scotland was estimated for the period 1965-1990. The purpose was to determine the particular age groups and causes of death responsible for the opposite trend of SDLE in the two countries. SDLE has been widening and narrowing in Japan and Scotland, respectively. The availability of complete and reliable data for these two developed countries facilitated the study. A method of decomposing the total SDLE into age and cause of death components was employed. About 40-60% contribution to SDLE was observed for ages after 65 years. Marked increase in the contribution of the 75+ age group and marked decrease in the contribution of ages 45-64 for Japan and Scotland, respectively, had a major effect on the widening and narrowing of SDLE in the two countries, respectively. The contribution of diseases of the circulatory system was the maximum until 1980 in Japan (< or = 1.8 years or 33.6%; cerebrovascular disease alone < or = 23.4%) and until 1990 in Scotland (< or = 3.1 years or 47.0%; ischemic heart disease alone < or = 42.0%). In Japan, the contribution of malignancy had a marked increased from 0.7 year (12.3%) to 2.0 years (32.6%), particularly for the trachea, bronchus and lung, while there was only a small increase in Scotland from 1.0 year (16.6%) to 1.2 years (19.8%) with an increase in the negative contribution of female breast malignancy. In Japan, the contribution of diseases of the respiratory system increased considerably from 0.5 year (8.5%) to 1.1 years (18.1%) while it decreased in Scotland from 1.0 year (16.5%) to 0.6 year (10.7%). About 60-75% of SDLE is due to the above three groups of causes of death. Malignancy and diseases of the respiratory system had a persistently increased contribution in Japan with resultant widening of SDLE by 0.9 year. Diseases of the circulatory system have always had a high contribution. On the contrary, in Scotland the contribution of diseases of the circulatory system and malignancy was practically unchanged and diseases of the respiratory system had a decrease with a consequent narrowing of SDLE by 0.4 year. Further epidemiological study is necessary to detect and analyze in detail the internal gradients (environmental and genetic-biological) of major contributor diseases to SDLE in Japan and Scotland.