Research on socioeconomic status, mediating factors, incident functional disability and healthy aging in older population

概要

Introduction: Previous studies have indicated that the association between SES and health were mediated by lifestyle and social factors. In Japan, SES-mediator-disability pathway might differ according to age because age-specified causes of disability are different; additionally, compared to developed countries, Indonesia (as a developing country) has different SES and public health problems, suggesting the SES-mediator-healthy aging pathway might be unique. However, neither the age-specified SES-mediator-disability association in Japan nor the SES-mediator-healthy aging association in Indonesia has been investigated yet. Higher SES is associated with better health and might be mediated by certain mediating factors. Thus, this study aimed to investigate the association between SES and health (incident functional disability and healthy aging), and whether mediating factors on these associations differ among the elderly population in both Japan and Indonesia.

Methods: 1) To investigate age-specified SES-mediator-disability association in Japan, we follow-up 8,680 Japanese individuals (≥65 years) living in Ohsaki city, Japan, for 9 years. In a baseline survey, we collected data on education level and potential mediators. Data on incident functional disability were retrieved from the Long-term Care Insurance database. Mediating effects were estimated using accelerated failure time model and a logistic regression model. 2) To investigate SES-mediator-healthy aging association in Indonesia, longitudinal data of 696 elderly Indonesian individuals (≥50 years) living in 13 different provinces in Indonesia were collected twice (2007 and 2014). In the 2007 survey, data on education level, monthly per-capita expenditure (PCE) and potential mediators were collected. Information on healthy aging was obtained both in 2007 and 2014. The mediating effect of mediating factors was estimated using the four-way effect decomposition.

Results: 1) Participation in community activities had the largest mediating effect (34.7%) on the association between education level and incident functional disability. This effect remained among those aged 65-74 years (19.9%) but became negligible among those aged ≥75 years. Other potential modifiable risk factors (such as smoking and drinking status) were also tested, but these showed only small mediating effects. 2) Higher education level was associated with healthy aging. However, monthly PCE was not associated with healthy aging among older Indonesian individuals. The associations between education level, monthly PCE and healthy aging were not mediated by modifiable factors.

Conclusions: Education level was significantly associated with better health in both Japan and Indonesia. This association was largely mediated by participation in community activities among elderly Japanese, but no mediators were identified in Indonesia.