1.3 Study Objectives and Significance

1.3.1 A Comprehensive View of Prior Study and Analyses

Findings from previous empirical research gave us a better understanding of the effect of SES on health status and mortality. Many social scientists and public health researchers also provided suggestions on how to promote health status and reduce the risk of premature death. Although results in available literature are not quite consistent, they have still laid the foundation for associations between SES and health. Socioeconomic inequalities in health exist all over the world, but vary by country, age, and gender. Some studies place the emphasis on understanding the mechanisms linking SES to health, including health status and mortality. Critical limitations of prior studies and analyses should be addressed in attempts to elucidate the association of SES-health and the mechanisms which this association acts on.

Firstly, looking at the target research population, the issues of health disparity by SES have been long known in western countries, but less in Asian countries, especially in Asian developing countries. Given that older adults constitute the majority of people who have health problems, special focus should be given to elderly people.

Secondly, looking at the methodological issue, structural equation modeling（SEM）is a statistical method that combines factor analysis and regression analysis. It can be applied to study both direct and indirect effects, and display the co-variation between all independent variables and dependent variables. To this point, it is superior to commonly used logistic regression analysis in previous studies in this field.

Thirdly, the perspective of this mechanism study is that few studies have explored the mechanism of how SES affects health status and survival time in an integrated perspective. A large number of studies have investigated the explanatory impact of healthy lifestyle on the SES-health status and on SES-mortality, however whether it applies to the elderly is still unclear. In addition, whether social interaction can mediate socioe-conomic differences in health among elderly people in Asian countries is also far from clear. Furthermore, little studies have taken distal, midrange and proximal factors of health into account simultaneously.

Lastly, indicators will be used on the basis of inconsistent findings in existing literature, partly due to multifarious indicators. Different indexes could set limitations on international comparisons.