Causal Structure for the Healthy Longevity Based on the Socioeconomic Status, Healthy Diet and Lifestyle, and Three Health Dimensions, in Japan

Abstract

This chapter aims to clarify the causal relationship between healthy life expectancy, socioeconomic status, dietary habits, lifestyle habits, and three health factors, as indicated by the WHO. In addition, the annual income threshold for couples to maintain a certain number of survival days will be clarified. Of the 16,462 elderly people aged 65 and over, 13,195 were included in the self-assessment questionnaire survey conducted in September 2001. A follow-up survey was completed in 2004, and 8,162 survivors were followed until August 2007. From a cross-lagged effects variation model, causal relationships were analyzed using longitudinal survival days between 2004 and 2007. After estimating a best-fit model, we discovered that current dietary and lifestyle habits did not determine healthy longevity. However, the survival days were more directly affected by three health-related dimensions three years earlier based on educational attainment and previous annual income indirectly. This study suggests that it might be of great importance for elderly individuals to emphasize income maintenance rather than focusing on diet and lifestyle improvements. In addition to showing a statistically significant relationship between income and survival days, we clarified that there is a threshold for income to maintain a certain number of survival days. For the elderly, it was 4.5 million yen(3,462 US $) for both sexes as a marital yearly income.