The results of the present study revealed that those having social support had a higher probability of achieving healthy aging than those lacking social support. To the best of our knowledge, this study is the first to investigate the association between emotional and instrumental social support and healthy aging in Japan.
We also conducted a sensitivity analysis by excluding those with better cognitive and motor function, but the results did not change substantially, which suggests that the benefits of social support in reaching healthy aging remained even in a relatively healthier population. In addition, we conducted an analysis using the combination of having or lacking emotional social support and instrumental social support. Interestingly, we found that the likelihood of healthy aging increased significantly in the group that had both types of social support but not in those who had only one type.
Only one study has investigated the association between social support and healthy aging, which was a cohort study following 4497 Norwegian participants (mean age: 52.7 y) for 22 years . They measured social support by asking two questions and categorized participants into the three groups of poor, moderate, and good social support. They found that people with good (but not moderate) social support had a significantly higher probability of healthy aging compared with those with poor social support. This observation is generally consistent with ours, where only those with both emotional and instrumental social support had a greater likelihood of healthy aging. We also found that social support was associated with a higher probability of showing each given component of healthy aging. Previous studies have also found that social support may have benefits for multiple health outcomes, such as lower risk of mortality [39, 40], functional disability , incident dementia [5–8], and depression , as well as a higher probability of life satisfaction [11, 12], which is consistent with the present findings.
This study has several strengths. First, we used a relatively large population-based cohort with a long follow-up period of 11 years. Second, our definition of successful aging considered not only physiological but, crucially, also psychological indicators, which have not been fully considered in previous studies. Third, we confirmed the consistency of our findings by conducting several sensitivity and stratification analyses.
The present study also has some limitations. First, among the four healthy aging components, only functional disability and depression were investigated in the 2006 baseline survey, and the remaining components of HRQOL and life satisfaction are unknown. Second, among the 9,947 participants who were eligible for follow-up, 1,715 were excluded from the 2017 analysis for the reasons of incomplete responses for social support or healthy aging assessment, questionnaire not returned, or invalid responses. Compared with the responders, these people might have received less social support. For instance, it is possible they may have been living alone and had no one to help them. Therefore, the association between social support and healthy aging could have been underestimated. Finally, information about social support is self-reported, which may have led to misclassification of the exposure.
Although Japan is among the countries with the longest life expectancy worldwide, a smaller proportion of older people in Japan have social support compared with those in other high-income countries . Thus, it is possible that some older Japanese people may not have as much social support as they need. The present study suggests that social support has great benefits for healthy aging but is limited to those who have both emotional and instrumental social support. This finding highlights the importance of sufficient social support in the promotion of healthy aging among older adults in an aging society.