Age and cause of death contributing to reduction of disparity in age-adjusted overall mortality between males in Okinawa and mainland Japan

Abstract

 Objectives We here propose a new index, the difference-change contribution proportion, to quantify contributions of age and cause of death to differences in age-adjusted overall mortality disparities between two groups over time. The present study was conducted with the aim of elucidating age and cause of death contributions to the recent decrease in disparity in life expectancy between males in Okinawa and mainland Japan. The longer-term goal is to apply the findings to developing appropriate preventive measures against diseases for Okinawa people.
 Methods Changes in disparity between age-adjusted overall mortality of male populations of Okinawa and Japan nationwide during a 15-year period, between 1985 and 2000, were measured and difference-change contribution proportions for age-adjusted overall mortality were computed.
 Results Causes of death that showed high difference-change contribution proportions included cerebral infarction (24.26%), cardiac failure (18.45%), other cerebrovascular diseases (15.11%), malignant gastric neoplasms (11.89%), ischemic heart disease (11.06%), hepatic disease (10.93%), suicide (5.71%), and diabetes (5.36%). Of these, cerebral infarction, cardiac failure, other cerebrovascular diseases, malignant gastric neoplasm, ischemic heart disease, and diabetes indicated high difference-change contribution proportions among seniors 65 years old and above, while hepatic disease and suicide ranked highly among the middle-aged.
 Conclusion The results of this study revealed the extent of age and cause of death contributions to the decreasing disparity observed between populations of Okinawa and Japan nationwide in male age-adjusted overall mortality. The causes of death and the age revealed by this study are critical to taking preventive measures against diseases. Moreover, this study confirmed that the difference-change contribution proportion is a useful method to quantify contributions of age and cause of death to changes in variation regarding life expectancy.