Factors affecting the longevity of total Japanese population

To clarify the relative importance of social life factors in longevity by age and sex, the authors analyzed the effects of 8 social life factors on life expectancy at birth and at ages 20, 40 and 65 years for males and females in 46 Japanese prefectures. The analysis was conducted twice at five-year intervals during the period of rapid urbanization using stepwise regression analysis after classification of twenty-two variables by factor analysis. The results indicated that urban residence was the major factor for life expectancy at birth for males and females and at ages 20 and 40 years for males; whereas proportions of old and young persons in the population were essential factors for life expectancy at age 40 years for females and at age 65 years for males and females. In addition, in males, proportions of old and young persons in the population also positively affected life expectancy at birth and at age 20 years; employment and high income factor positively affected life expectancy at birth and at ages 20 and 40 years. Unique position of Japan in comparison with Western countries regarding social life factors for longevity is discussed in the light of these findings.