Factors influencing happiness in the elderly based on the Anderson model

： Background: The happiness of elderly people is an important indicator of successful aging. Research shows that happiness among the elderly is not only affected by physical conditions, social relations and other factors, but is also used as a measure of other aspects of happiness. This study examined the relationship between happiness and social relationships, contextual characteristics, and the medical outcomes of the elderly in China. Methods: A total of 669 subjects over the age of 60 years were randomly selected from 13 cities in Heilongjiang province and surveyed using questionnaires. We used a structural equation based on the Anderson model to analyze the factors influencing happiness in the elderly. Results: The main factors for happiness in the elderly were social relationships (P = 0.51), contextual characteristics (P = 0.26),

The fifth section mainly evaluated medical treatment of the elderly. Specifically, the participants were asked whether they had been hospitalized in the last year. They were also asked whether they have had chronic diseases in the last year. In both cases, if they had, the answers were scored with 1 point, and otherwise they were scored with 0.

Data analysis
Data were processed using Epidata and were double-entered to ensure quality. Sample characteristics were analyzed using SPSS V. 19.0. Descriptive statistics were reported for socioeconomic and demographic characteristics, physical health, and life satisfaction in urban and rural areas. According to the actual situation of the elderly in China, we used social relations to replace healthy behavior in Anderson's model. In addition, demographic variables could not be included in the structural equation as explicit variables, so the path of individual characteristics was excluded. Finally, the structural equation model was used to measure the relationship among contextual characteristics, social relationships, medical outcomes, and happiness. The following indices were used to evaluate the overall model fit: the goodness-of-fit statistic, the goodness-of-fit index (GFI), the Tucker-Lewis index (TLI), the comparative fit index (CFI), and the root mean square error of approximation (RMSEA). Table 1 shows the socioeconomic and demographic characteristics of the participants. In the sample, 47.3% respondents were male, and 52.7% were female. The age of the elderly was mainly concentrated between 60 and 70 years old (50.6%), 27.9% were between 70 and 79 years old, and 21.4% were older than 80 years old. Most respondents had children (94.7%). The proportion of the elderly who owed property was 61.3%. In addition, the monthly income of the elderly was such that 35.3% had less than 999 RMB, 19.8% had between 1000 RMB and 1999 RMB, 27.7% had between 2000 RMB and 2999 RMB, and 17.1% had more than 3000 RMB.

Structural equation modelling
The Andersen model showed that each coupled dimension was related. We connected every two exogenous variables to build a structural equation model for happiness (Figure 1). The regression weights and standardized regression weights are shown in Table 2. As can be seen from Table 2, the path of satisfaction with community medical institutions was not statistically significant (p = 0.193, ＞ 0.05), and so the path was eliminated. In light of this, we rebuilt the model after correcting it ( Figure 2). The regression weights and standardized regression weights of this model are shown in Table 3, showing that every path is meaningful. The goodness-of-fit index of the model was suitable for the requirements of the structural model ( Table 4).
The path coefficient from social relationships to happiness was 0.507, which is statistically significant at p < 0.001. Social relationships thus had a positive effect on elderly happiness. The relationship between contextual characteristics and happiness was 0.256, which is statistically significant at p < 0.001. Thus, contextual characteristics had a positive effect on elderly happiness. The relationship between medical outcomes and happiness was 0.232, which is statistically significant at p < 0.001. Thus, medical outcomes had a positive effect on elderly happiness.

Discussion
The Anderson model provides a mature framework in which social relationships, contextual characteristics, and medical outcomes were included to observe their impact on elderly happiness. In recent years, the happiness of Chinese people has significantly improved 18 . The results of this study show that social relations, environmental factors, and medical outcomes have the greatest impact on the happiness of the elderly.
First, Table 3 shows that social relationships are the most influential factors for the happiness of the elderly. This is consistent with the results of Moeini 1920 . A good social support network can increase quality of life 21 , thus improving happiness. Xiaotong proposed the difference model to explain the composition of China's social network. Compared to Western society, relatives account for a higher proportion of Chinese social networks 22 . Research has shown that satisfaction with interpersonal relationships and support from friends importantly impact happiness. Due to family and work, adult children rarely have time to accompany their parents 23 , so the role of the community with regard to the happiness of the elderly should be emphasized. In developed countries, social isolation is a problem that needs attention. The elderly are vulnerable to a loss in social relationships, since community resources to form social networks in old age are limited 24 . Reducing social isolation of the elderly and promoting their integration into society is an urgent problem.
Second, contextual characteristics played the second-biggest role in the happiness of the elderly, according to our study. In this dimension, the main influential factor was monthly income, which is consistent with the results of Shamsk and other studies 2526 . According to the Easterlin paradox, personal income is closely related to happiness. The theory states that at the micro-level, personal income is positively correlated with happiness. At the macro-level, however, there is no significant correlation between a country's economic growth and national happiness. Although Junqiang questioned the applicability of this theory to China, Easterlin's subsequent survey of developing countries showed that economic growth and national happiness have a U-shaped trend. This theory has been confirmed in a study specifically aimed at China. Since 1990, China's resident happiness index has been on a downward trend, dropping to its lowest level between the years 2000 and 2005, and then slowly picking up. Therefore, the revised Easterlin paradox still applies to China. For the elderly, there is a positive correlation between personal income and happiness. In 2016, no city in Heilongjiang was among the top ten cities in China's urban happiness index. According to the official website of China's National Bureau of Statistics, in 2016, Heilongjiang ranked 18th in terms of per capita disposable income. Therefore, we should pay more attention to the income of the elderly to improve their happiness.
Finally, there is a correlation between medical outcomes and the happiness of the elderly, and there is a positive correlation between self-assessment of health and happiness, which is consistent with the results of other research 2728 . Indeed, the deterioration of health will lead to a decline in happiness 29 . According to our survey, elderly who were not hospitalized or ill were happier. This is consistent with the results of a survey 30 . A decline in health as a result of stroke or cancer, for example, negatively affects happiness 31 . The relationship between disease and happiness is complex, and disease can affect happiness through its impact on health. The extent of disease has various effects on the ability of the elderly to care for themselves, which, in turn, affects their overall level of happiness 32 . According to hedonic adaptation theory, however, people adapt to disease over time, and the effect of physical health on happiness gradually decreases 33 . In addition, mental health must be considered. Better screening, diagnosis, and treatment for depression, social phobia, and other mental disorders that afflict the elderly cannot be ignored.
The influence of contextual characteristics, social relationships, and medical outcomes on the happiness of the elderly is not independent. Retired elderly, especially those in poor health, spend most of their time in the community 34 . Due to the physical health and family life of the elderly, social networks in later years are shrinking. Therefore, interpersonal communication in the community and elderly satisfaction with the acquisition of medical resources are important. They help the elderly to maintain their health and reduce their loneliness.

Conclusions
Increasing attention has been paid to the happiness of the elderly. Regarding this, we should attach importance to social communication networks for the elderly. Good social communication can reduce the sense of social isolation. In addition, sufficient medical resources should be provided for the elderly to ensure their health and improve their well-being.

Declarations
Ethics approval and consent to participate Approval for this study was granted by the Institutional Research Board of Harbin Medical University. The data were collected anonymously. Respondents were assured that participation in this survey was voluntary, with the return of completed questionnaires taken as consent to participate.

Consent for publication
All presentations of case reports received consent for publication.
Availability of data and materials Data will not be shared. We promised not disclose information regarding the respondents when we signed the informed consent form.

Competing interests
The authors declare that they have no competing interests.

Funding
This study was funded by the National Science Foundation of China (NSFC), No. 71573066/G0308.