Preface

The aging of the population is increasing worldwide due to increasing longevity and declining birth rates. Japan leads the world in the pace of aging，with currently over 1 in 5 individuals aged 65 years and over. On the positive side，Japan has ranked first in terms of life expectancy at birth，especially for females. On the negative side，significant aging of the population has increased the number of older people who are bedridden，have dementia，or are in need of long-term care（LTC）or support for daily living. Thus，whether longer life expectancy is accompanied by better health measures within aging populations is becoming a great concern. Shifting the previous narrow focus on length of life，in recent years，healthy life expectancy（HALE）has been increasingly used to measure an individual’s health status according to a series of indicators，such as self-rated health（SRH），disability，and disease consequences. The primary purpose of this book is to investigate Japanese HALE and to analyze the consequences of physical disability and comorbidity on HALE at the individual level in the elderly.

Data from western nations show a well-established inverse gradient between socioeconomic status（SES）and mortality or morbidity. Because the use of SES and health indicators may depend on social context，whether health-related SES variables would diminish，persist，or grow with age is disputed. Although Japan has been long heralded as an egalitarian and largely middle-class society，the trend towards greater socioeconomic equality in terms of health has been less obvious since the 1990s. This trend has coincided with a gradually increasing income inequality. Thus，the second purpose of this book is to examine the SES’s impact on HALE in the Japanese elderly，with a special emphasis on direct and indirect effects interacting with gender，age and location factors. A series of models estimating the structural causal relationships between individual SES，physical health，and HALE among the Japanese elderly will be validated.

In the LTC field，there is a consensus that disability among the elderly is the primary factor driving the demand for LTC services，leading to the Long-term Care Insurance Law introduced by the Japanese government in April 2000. The third purpose of this book is to explore the structural causal relationships between SES，LTC needs，physical health and HALE in elderly individuals，which would have implications for LTC management in the Japanese elderly. Results from the book may also construct lessons for the evaluation of the nation’s health and the impact of health policies for other countries as well.

This book is organized as follows. Chapter 1 provides an introduction to five key concepts in the development of this book：population aging，HALE，SES，physical health and LTC. Furthermore，I discuss the existing theories about population health status changes and theoretical hypotheses about SES effects on HALE due to the aging of the population. Using findings from the literature，an international comparison，the trend over time，as well as gender and age differences will be presented. Subsequently，I will address the rationale，objectives，methods，and hypothetical model of the book.

Chapter 2 presents an empirical study on prefectural mortality in relation to socioeconomic status and long-term care in Japan. Prefectures in Japan were used as units of analysis and 7 indicators were obtained from multiple data sources，which were published by government organizations and public institutions for years centering on 1995，2000，and 2005. Based on the correlation and linear regression analyses，factors that explain the mortality，LTC and SES variation demonstrated that prefectures with higher socioeconomic levels and lower LTC application rates had lower mortality of male and elderly people in Japan. With respect to gender differences，prefectural SES and LTC displayed significant associations with mortality for men but not for women.

Chapter 3 presents a study on healthy life expectancy in relation to socioeconomic status and physical health among Japanese elderly. A questionnaire survey was conducted with all residents aged 60 years and older in 16 municipalities of Japan where we could obtain the help of public health centers in 1998. Participants were followed until June，2000. In all，15，254 individuals were analyzed. Data analysis was performed by survival analysis and structural equation modeling（SEM）using SPSS 19.0 and AMOS 17.0 for Windows. The data indicated that SES was the determinant of HALE；lower SES of the elderly was associated with an increase in mortality directly and with a decrease in SRH indirectly via physical health status. The significant distribution of SES，physical health and HALE were found by gender，age and location among the elderly people in 16 municipalities of Japan.

Chapter 4 is a study on healthy life expectancy in relation to socioeconomic status，physical health and long-term care among Japanese elderly，and aims to elucidate the effects of SES，physical disability，comorbidity，and LTC on HALE among the suburban elderly in Japan. A questionnaire survey was conducted among all residents aged 65 years and older in a suburban area of Tokyo in 2001，with two follow-up studies being conducted in 2004 and 2007. In all，7，905 respondents were included as analysis subjects. Data analysis was performed using survival analysis and SEM. The results indicated that improvement in SES of the elderly works toward extending their life expectancy of living with good health via improving daily living capabilities and preventing the needs for LTC. Significant gender differences were found in the relationship between SES and HALE among the Japanese suburban elderly. Furthermore，with increased age，declining physical health within the high SES category appeared to override the significant effects of SES on HALE for the Japanese suburban elderly.

Chapter 5 summarizes the most important findings and draws conclusions as follows：（1）A SES disparity in terms of HALE was found in Japan，while SES’s impacts on HALE in the elderly represented a significant direct effect；（2）In addition to the direct effects，indirect effects of SES on HALE in the elderly were transferred by physical health，and LTC levels；（3）There were significant model differences in terms of gender，age，and location of the elderly in Japan. In this section，I also elucidate the new insights that this book has generated，and point out the questions that still remain as well as new questions that have originated. Finally，there are certain issues for future studies in terms of external validity and reliability.

In Japan’s aging society，a rapid increase in the elderly population is inevitable. This study promotes a deeper understanding and awareness of socioeconomic HALE determinants interacting with gender，age and location，which will contribute to the development of a multi-sectorial health policy to improve the overall health of the elderly people in Japan.