A comparison of correlates of self-rated health and functional disability of older persons in the Far East: Japan and Korea

Abstract

Self-rated health and physical functioning are recognized as important indicators of health in older persons. Rarely, however, there have been studies done which examine cross-cultural differences in the health of older people using these measures, especially among non-Western countries. The objective of this study was to examine patterns of association of self-rated health and functional disability of Japanese and Korean elderly people living in the community, using nationwide surveys of persons aged 60 years or over. There were striking similarities in the general pattern of associations with covariates. In the multivariate analysis, age, work status, comorbidity, depressive symptoms, life satisfaction, hospitalization, and functional disability were strongly associated with self-rated health in both populations. For functional disability, older age, female, low social contact, depressive symptoms, poor life satisfaction, and poor self-rated health were found to be significantly associated. Some differences in the structure of associations with self-rated health, however, were noted. Women tended to assess their health more favorably than men in Korea, but in the Japanese elderly gender differences disappeared when other variables were taken into account. Health-related variables tended to be more closely associated with functional disability in the Japanese sample. An overall similarity, however, in the pattern of associations of these measures supports their utility in assessing and comparing the health of older populations in this region.

Introduction

With population aging emerging as a worldwide phenomenon, researchers and policy makers are increasingly turning to cross-national research to better understand the health of the nation's older population. For scientists comparative analysis using nation-level data enhances understanding of differentials in health status among nations and the dynamics of population aging and its impact on health and health care. It is also useful in assessing the generalizability of findings and validity of interpretations across diverse cultural settings (Liang and Jay, 1992). Cross-national comparisons of population health, if done appropriately, may also aid policy makers in evaluating the performance of the nation's health care system (Kovar et al., 1995, World Health Organization, 2000) and facilitate the development of effective policies and programs that promote the health of older people (National Research Council, 2001).

Most cross-national research on aging and health reported thus far, however, have been largely based on comparisons of Western populations or have looked at ethnic groups within a specific country. Relatively few research exist that have examined health status of elderly populations in Asia, where the growth in the number and proportion of older persons is found to be one of the fastest among the world's major regions (Myers, 1990).

Countries in East and Southeast Asia, in particular, are aging most rapidly (Kinsella and Velkoff, 2001). In the Far Eastern part of the region, Japan and Korea top the rank in the rate of population aging. Japan is one of the world's foremost aged societies, with over 17% of the population being aged 65 and older in 2000. It took Japan 26 years, from 1970 to 1996, for its 65+ percentage to double from 7 to 14%. In comparison, Korea still has a relatively young population composition, with 7.2% of the population in the 65+ age stratum (National Statistical Office, 2001). Recent projections, however, indicate a faster aging rate than in Japan, with an estimated period of 19 years to reach 14% by the year 2019. The pace at which population aging is progressing in these two countries is alarming compared with that of Western nations. The 7–14% rise in the 65+ population occurred over a period of 115 years (1864–1979) in France and is expected to take 69 years (1944–2013) in the United States.

Moreover, previous efforts at comparisons between the nation's elderly have largely focused on gross indicators of health, such as morbidity and mortality. Although important, these measures do not reflect the older individual's perspectives on his or her overall health. They further fail to encompass physical functioning, an important indicator of the ability for older persons to maintain independence in the community; also increasingly being recognized as a ‘vital sign’ for geriatric care (Bierman, 2001).

Self-reports of health, in terms of self-rated health and physical functioning, are key indicators of health and well-being of older adults. They provide valid information as to the older person's general health status and dependency or care needs. Being simple in form and easy to administer through questionnaires or interviews, these person-centered measures complement more ‘objective’ assessments performed in the doctor's office. These perceptions about one's health and functional capacity, moreover, are significantly associated with adverse health outcomes of aging. Studies of older persons have found self-rated health and physical functioning to be highly correlated with chronic diseases or symptoms (Mulsant et al., 1997, Woo et al., 1998, Fried et al., 1999, Bryant et al., 2000), hospitalization (Mor et al., 1994, Kennedy et al., 2001), functional decline or disability (Mor et al., 1994, Idler and Kasl, 1995, Lawrence and Jette, 1996, Lee, 2000), and mortality (Idler and Benyamini, 1997, Scott et al., 1997, Lee, 2000).

Until now, there have been very few cross-national comparisons examining the correlates of self-rated health and physical functioning of older people (Liang et al., 1991, Kovar et al., 1995, Lamb, 1996, Jylhä et al., 1998). And to our knowledge, there has been no comparisons done using national samples of older populations in Far East Asia. Findings of similarities in the structure of these measures, in regard to their associated factors, would enhance the generalizability of results of existing research and support their utility as a comparative health assessment tool in this regional setting. In this study, using national surveys, we examined patterns of associations between self-rated health and functional disability and sociodemographic and health-related correlates among older persons in Japan and Korea.