α-indexの動向とその要因の検討

Abstract

The α-index, a qualitative index of infant mortality, is the ratio of the number of neonatal deaths under 28 days of age to that of infant deaths under one year of age. The α-index is based on the Annual Vital Statistics Reports compiled between 1900 and 1990 by the Statistics and Information Department, Minister's Secretariat, Ministry of Health and Welfare. We evaluated the change of α-index and factors related to neonatal mortality and infant mortality. The findings of this study are summarized as follows. 1. Except during World War II, the α-index decreased gradually until 1976, after which increased each year until 1990. 2. Since 1977, the decrease of neonatal mortality rate was greater than that of infant mortality rate. 3. The decrease of neonatal deaths attributed to "birth trauma" and "premature infant" effectually contributed to decreasing neonatal mortality rate. 4. Relative increase of infant mortality attributed to "accidents and adverse effects" and "other external causes" slightly attenuated the decrease of infant mortality rate. The α-index is an effective index which indicates the "death-velocity-coefficient" of various diseases. It is suggested that health management and parental health education programs should emphasize "accidents and adverse effects".